JP2006504900A - Method and apparatus for diagnosing an injector - Google Patents

Abstract

A tester for conveniently diagnosing a fuel injector of an internal combustion engine is described. The fuel injector includes an injector coil that is charged during the energization period. The tester calculates the difference between the two sample signals obtained during the energization period. The tester determines a first operating condition of the injector based on this difference and determines a second operating condition based on the level of at least one of the sampled signals.

Description

FIELD OF THE DISCLOSURE This disclosure relates generally to a method and apparatus for determining the operating status of a coil, and more particularly, evaluating a fuel injector having an injector coil based on signals obtained during its operation. The present invention relates to a failure detection method and apparatus for performing the above.

BACKGROUND Internal combustion engines employ various numbers of fuel injectors to supply fuel. For non-diesel engines, electronic fuel injectors are the most commonly used fuel injectors. An electronic fuel injector may have a plurality of electromagnetically actuated fuel injection valves that are sequentially filled with a determinable amount of fuel during a fuel metering period and fuel is engineered during subsequent periods. It is supposed to be injected into.

  FIG. 1 is an exemplary circuit for controlling the operation of a fuel injector. An injector coil 10, such as a solenoid coil, is disposed in association with each injection valve and is used to control its opening and closing. The injector coil 10 has one end coupled to the voltage source 12 and the other end coupled to the switch 14. Switch 14 controls the coupling of injector coil 10 to ground. The on / off of the switch is controlled by a controller or processor such as a PCM (powertrain control module), ECU (electronic control unit), or ECM (electronic control module).

  The injector coil 10 is controlled such that the injector coil activates or retracts a movable member such as a pintle disposed on the injection valve. When switch 14 is closed, current flows through the injector coil. The current energizes the injector coil or generates a magnetic field that activates the pintle of one of the injection valves so that fuel is injected through the valve opening into the combustion chamber of the cylinder. When switch 14 is open, no current flows through the injector coil 10. The pintle thus returns to its original position and closes the injector valve.

  It is necessary to evaluate the condition of the injector. There is also a need to automatically detect defective injectors. There is also a need for a simple and convenient process for determining the operation of the fuel injector without using a difficult to use current probe.

SUMMARY This disclosure describes a method and apparatus for conveniently diagnosing a fuel injector having an injector coil and a power source that charges the injector coil during an energization period. An exemplary tester monitors the signal from the fuel injector. The tester diagnoses the fuel injector based on the monitored signal. The tester includes a data port for receiving signals, a data storage device, and a data processing unit coupled to the data port and the data storage device. The data storage device has a command, the command being transmitted to the tester upon execution of the command by the data processing unit, a first signal representing a first energization state of the injector coil during the energization period, And a second signal representative of a second energization state of the injector coil during the period. The data processing unit then determines a first operating condition of the injector based on the level difference between the first energized state and the second energized state.

  In one aspect, the first and second signals represent the voltage on the injector coil during the period in which the voltage source sends current to the injector coil. These signals may be obtained before or during conduction of the diagnostics of the injector. These signals may be stored in a data storage device and accessible by the data processing unit. The data processing unit calculates a difference between the first signal and the second signal, and determines whether the difference falls within a predetermined range. If the difference is outside the predetermined range, the tester indicates that the injector coil has a high resistance.

  Optionally, the inspector may be further configured to determine a second operating condition of the injector based on at least one level of the first energized state and the second energized state. For example, the data processing unit may determine the injector voltage obtained during a time when the voltage source sends current to the injector coil to determine whether the injector current is lower than a threshold voltage, e.g., a voltage close to zero volts. You may access the data you represent. If the injector voltage is higher than the threshold voltage, the tester indicates that the injector coil has an unacceptable resistance. For example, the tester may indicate the injector coil as shorted or partially shorted.

  This disclosure is shown by way of illustration and not limitation in the figures of the accompanying drawings. In the drawings, like reference numerals refer to like elements.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring this disclosure.

  An exemplary tester for conveniently diagnosing an injector having an injector coil is disclosed. This inspector determines various operating conditions of the injector based on the signals generated thereby. One of the signals used by the tester is the injector coil voltage relative to ground. FIG. 2 shows the waveform of the signal displayed on the oscilloscope with a large scale, for example, a 50 volt scale. The injector coil voltage represents the energization status of the injector coil and can be determined at any point between the injector coil and the switch or any known to those skilled in the art to determine the energization status of the injector coil. It may be measured at other equivalent points. For example, the voltage waveform in FIG. 2 is obtained from point A in FIG.

  The operation of the fuel injector can be understood by referring to FIGS. The waveform of FIG. 2 includes five sections, namely sections A, B, C, D and E, but section B and section D extend only in a very short time. In section A, switch 14 is opened and no current flows through injector coil 10. The measured injector voltage is approximately the same as the voltage of the voltage source 12. In section B, a control signal from the ECU or PCM closes switch 14, which pulls the injector voltage closer to ground. Current begins to flow through the injector coil 10 and the voltage source 12 begins to energize the injector coil 10. The current flowing through the injector coil 10 increases steadily in section C and approaches the saturation current level. The current passing through the injector coil 10 builds a magnetic field sufficient to operate a standard pintle on the injection valve so that fuel is injected into the cylinder's fuel chamber through the valve opening. Section C is usually called an energization period.

In section D, a control signal from the controller or data processor opens the switch 14. No current flows through the injector coil 10. The magnetic field established by the injector coil will therefore collapse. The energy storage in the injector coil 10 is released as a voltage pulse induction kick that exceeds the level of the voltage source 12. At this point, the magnetic field is weakened and is no longer sufficient to operate the pintle. In section E, the pintle is released. Due to the mechanical movement of the pintle relative to the coil, a voltage bulge occurs in section E.

  The waveform shown in FIG. 2 is observed using a large voltage scale of 0 to 75 volts. Under such an observation scale, when the injector coil 10 is energized in section C, the injector voltage appears constant. However, when this waveform is observed with a minute scale such as about 0.00 volt to 2.00 volt level, the waveform in the section C shows different characteristics.

  FIG. 3 is a waveform showing the same injector voltage as shown in FIG. 2 on a fine scale. Signals greater than 2.0V are clipped. Section C ′ in FIG. 3 is comparable to section C in FIG. 2, which corresponds to the injector voltage when the injector coil is energized. While section C in FIG. 1 shows a substantially constant voltage level, section C ′ in FIG. 3 shows that the injector voltage actually changes over time while the injector coil is energized. Yes. The inspector determines the operating state of the injector based on the characteristics of the injector voltage obtained while the injector is energized.

  4a and 4b show the injector voltage waveforms obtained from two injectors from the same vehicle, respectively. The injector of FIG. 4a has a high resistance, while the injector of FIG. 4b is normal. Two sample voltages VT1 and VT2 are obtained during the period when the injector coil is energized. In one embodiment, VT1 is sampled within 200 ms after the start of energization of the injector coil, and VT2 is sampled within 200 ms before the end of energization of the injector coil. The voltage difference between VT2 and VT1 is defined as “ΔV”.

  During the period when the injector coil is energized, it is observed that the injector voltage for the high resistance injector (FIG. 4a) is low or absent ΔV. On the other hand, the injector voltage for a normal injector (FIG. 4b) has a ΔV of about 0.50 volts. For this reason, the tester can determine whether the injector has a normal resistance or a high resistance based on the value of ΔV.

  The tester receives a voltage signal from the injector by means of a signal probe coupled thereto and determines the ΔV for the injector accordingly. To determine whether the injector has normal resistance, the inspector determines whether the injector ΔV is within a predetermined voltage range corresponding to the vehicle model or injector type being inspected. to decide. The predetermined voltage range corresponding to each vehicle model and / or injector type can be obtained empirically. The range of values can be stored in the data storage device of the tester. For example, a predetermined voltage range of 0.15 volts to 0.85 volts may be used for vehicles having 10-20 ohm injectors. If ΔV is outside this range, the data processing unit determines that the injector under test has an abnormal injector. On the other hand, if ΔV falls within the predetermined voltage range, the data processing unit indicates that the injector resistance may be acceptable. The determination result may be sent to a display monitor.

  FIG. 5a shows the voltage waveform of an injector having a lower resistance than normal, and FIG. 5b shows the voltage waveform of a normal injector. Although the waveform of FIG. 5a appears to have an acceptable ΔV, unlike the normal waveform of FIG. 5b, the waveform of FIG. 5a has not pulled the signal close to ground. Thus, the level of injector voltage obtained during energization of the injector coil is an indicator of whether the injector has a resistance less than that of a normal injector.

As described above, the tester samples the two injector voltages VT1 and VT2 and calculates ΔV during the period when the injector coil is energized. The same sampled voltage can be used to determine whether the injector has a resistance lower than that of a normal injector. In one embodiment, VT1 is used. If VT1 is greater than a predetermined voltage value, the tester determines that the injector under test has a resistance that is less than the resistance of a normal injector. In one example, the inspector indicates that the injector is shorted or nearly shorted. In other cases, the injector is considered to have normal resistance.

  The predetermined voltage value used to determine the injector status may vary from vehicle model to injector type. Predetermined values for different vehicle models or injector types can be determined empirically and stored in the inspector. For a typical SFI (sequential fuel injection) injector having a resistance in the range of 10Ω to 20Ω, the predetermined value may be set to 0.5 volts.

For an exemplary injector having a resistance in the range of 10Ω to 20Ω, the injector voltage during which the injector coil is energized may need to satisfy the following equation: VT2−VT1 = V, Medium, V falls between 0.15 volts and 0.85 volts. 0.0 <VT1 <0.5 volts.

  The above example uses only two sample voltages to determine if the injector has a resistance higher than that of a normal injector, but other numbers of sample voltages can be used to achieve the same result. It is also possible to use it. For example, three or more sample voltages may be measured during the energization period. Only the maximum and minimum voltages are retained and other sampled voltages are discarded. Next, ΔV is calculated based on the held voltage.

  Limitations in obtaining the injector voltage can also be used. For example, VT1 may be obtained only from the first half of the energization period, and VT2 may be obtained only from the second half of the energization period.

  In addition to determining whether ΔV falls within a certain voltage range, other determination methods based on variations in injector voltage may be used to evaluate the operating condition of the injector. For example, the threshold value or the threshold range may be compared using the rate of voltage change during the energization period. Thresholds or threshold ranges corresponding to different vehicle models or injector types may be obtained empirically. Other methods based on injector voltage variations may also be employed without departing from the broader spirit and scope of this disclosure.

Inspector Hardware Overview FIG. 6 shows an exemplary inspector 60 used to perform fuel injector diagnostics as described above. This inspector may be a stand-alone inspector or part of an onboard vehicle computer. The tester 60 includes a data port 61 for receiving signals, a data storage device 62 for storing data and instructions, and a data processing unit 63 coupled to the data port 61 and the data storage device 62. Optionally, the tester provides a display 64, such as a monitor or LCD (Liquid Crystal Display), and a user interface that communicates with the operator of the tester 60, such as a keyboard, mouse, push button, touch screen panel or voice control device. An input device 65 may be included. The data processing unit 63 performs various tasks by executing machine readable instructions such as signal processing, signal level calculation, providing a user interface to the operator, displaying instructions and diagnostic results, and receiving commands from the operator. It is configured as follows.

Data port 61 includes one or more data channels for connection to sensors, signal probes, and / or peripheral devices. Various types of data channels may be implemented, for example via USB port, PS / 2 port, serial port, parallel port, IEEE-1394 port, infrared communication port, native port, and / or data transmission network 70. There is a network connector 66 for connecting to a remote computer 75. Signals received from data port 61 are coupled to data processing unit 63 and data storage device 62 for storage and / or processing.

  The data storage device may include volatile and / or non-volatile memory. Volatile memory 67 includes random access memory (RAM) or other dynamic storage for storing instructions and information to be executed by the data processing unit. Volatile memory 67 may also be used to store voltage readings, primary variables or other intermediate information during execution of instructions to be executed by the data processing unit. Non-volatile memory 68 may include a read only memory (ROM), hard disk, CD-ROM, DVD-ROM or other static storage device for storing static information and instructions. Data storage device 62 may be a machine readable medium (not shown), such as a floppy disk, flexible disk, hard disk, magnetic tape or any other magnetic medium, CD-ROM, any other optical medium, punch From a card, paper tape, any other physical medium with a hole pattern, RAM, PROM, EPROM, FLASH-EPROM, any other memory chip or cartridge, or any other medium readable by the data processing system , Data and / or instructions may be read.

  The tester 60 is controlled in response to the data processing unit 63 executing one or more sequences of one or more instructions contained in the data storage device 62. Such instructions may be read into another type of memory device from another machine readable medium. Execution of the sequence of instructions causes the tester 60 to perform a process as described herein. In alternative embodiments, wiring circuitry may be used instead of software instructions or in combination with software instructions to implement this disclosure.

  In one embodiment, during command control, the tester 60 receives a voltage signal from a signal probe coupled to the injector to obtain a signal representative of the injector voltage. Multiple voltage signals may be sampled and stored in the data storage device. The sampled signal includes at least a first injector voltage and a second injector voltage obtained during a period in which the voltage source sends current to the injector coil. The sample signal may include, for example, VT1 and VT2 as shown in FIGS. 4a and 4b. The tester 60 then determines whether the injector has a resistance higher than that of a normal injector based on the voltage difference (ΔV) between VT1 and VT2, as described above.

  The tester 60 determines whether the injector has a resistance lower than that of a normal injector based on the injector voltage obtained during the period when the voltage source sends current to the injector coil, as described above. May be determined separately. The data processing unit may, for example, compare the threshold value obtained from a remote computer 75 stored in the data storage device 62 or connected to the tester via the data transmission network 70 with VT1. Good.

  It is more convenient to use a voltage signal to determine the operating situation than to use a current signal. This is because it is not necessary to connect a difficult-to-use current probe intrusively or non-intrusively. The voltage signal may be obtained using a simple voltage access point near the PCM or ECU that controls the injector.

FIG. 7 is a flow chart illustrating steps for diagnosing an injector coil using an exemplary inspector as described above. The user first connects the voltage probe of the tester to point A as shown in FIG. 1 (step 701). The inspector obtains an injector voltage waveform during operation of the vehicle (step 703). The tester then identifies sample voltage signals VT1 and VT2 (step 705). The tester then compares VT1 to a first threshold, for example 0.5 volts (step 707). If VT1 is greater than the first threshold, the tester determines that the injector coil has a resistance that is less than the resistance of a normal injector (step 09). In other cases, the tester continues to calculate the voltage difference ΔV between VT1 and VT2 (step 711). The inspector then compares ΔV to a second threshold, eg, 0.15 volts, to determine whether the injector coil has a resistance that is higher than an acceptable level (step 713). If ΔV is less than the predetermined value, the tester indicates that the injector coil has a resistance greater than that of a normal injector (step 715). Otherwise, the inspector indicates that the injector coil is normal (step 717).

  The above diagnosis is in one embodiment a test to determine if the injector coil has a resistance lower than the resistance of a normal injector, and the injector has a resistance greater than the resistance of a normal injector. Combined with the test to determine whether or not, the two tests can be performed separately.

  FIG. 8 is a flowchart illustrating the steps of another embodiment for diagnosing an injector coil using an exemplary inspector as described above. In step 801, the tester obtains an injector voltage waveform. In step 803, the user verifies whether there is a normal voltage source. For vehicles that use injectors with a resistance in the range of 10Ω to 20Ω, the voltage source is 13.2 volts to 14.6 volts. If the voltage source is not stable and the voltage source is not within the normal voltage range, the user can check the voltage source, such as adjusting the open voltage source or open circuit problem, if necessary, Repair is required (step 821).

  If the voltage source is normal, the tester determines whether the ECU / PCM energizes the injector by periodically turning the injector on or off (step 805). Otherwise, the tester may alert the user to verify the reason. There are many reasons why the ECU / PCM will not turn the injector on and off even if the voltage source is normal. For example, failure in the anti-theft system, absence of rpm signal, etc. The most common reason that a particular injector driver cannot operate consistently is a faulty ECU / PCM injector driver or a short circuit of the injector. In some cases, a short circuit of the injector can cause damage to the ECU / PCM injector driver. After repair of a shorted injector and / or its circuit, the PCM / ECU often functions normally. This is because the PCM / ECU shuts off certain injector drivers to protect each individual transistorized injector driver.

  If the tester determines in step 805 that the ECU / PCM is properly energizing the injector, the tester retrieves the sample voltages VT1 and VT2 and calculates ΔV based on VT1 and VT2 (step 807). In step 811, the tester compares VT1 to a first threshold, eg, 0.5 volts. If VT1 is greater than the first threshold, the tester alerts the user to check the PCM / ECU power ground. If the grounding condition is normal, the injector indicates that the injector coil has a resistance that is less than the resistance of a normal injector (step 825). The inspector may alert the user to check and replace the injector coil.

  If the comparison at step 811 determines that VT1 is less than the first threshold, the tester then compares ΔV to a second threshold, eg, 0.85 volts, and It is determined whether the vessel coil has a resistance higher than an acceptable level (step 813). If ΔV is greater than the second threshold, the tester indicates that the injector circuit has a low resistance, that is, a shorted or partially shorted injector / circuit (step 827). .

  If the tester determines that ΔV is less than the second threshold, the tester then determines whether ΔV is less than a third threshold, eg, 0.15 volts (step 815). . If ΔV is less than the third threshold, the tester indicates that there is a high resistance in the injector circuit (step 829). The inspector may alert the user to manually check the injector resistance. The resistance must not exceed 20 ohms. In other cases, replacement of the injector coil is required. The inspector may also alert the user to check the injector harness connection. This is because high resistance is often caused by corrosion at the injector terminal connection.

  If, at step 815, the inspector determines that ΔV is greater than the third threshold, then the inspector then determines that the injector has an acceptable resistance (step 817).

  In another embodiment, even if the injector is shown as having normal or abnormal resistance, the inspector performs a manual comparative analysis on the injector to determine whether the injector has normal resistance. The user may be warned to make a determination. For example, if ΔV falls within 20% of the threshold, the inspector generates a message indicating that a manual inspection for injector resistance may be necessary. The same approach may be applied to the determination of VT1 or other signals having a threshold.

  Although the above example describes the evaluation of an injector coil located in a fuel injector, the application of the present invention and apparatus is not limited to a fuel injector. A similar approach can be used to determine the operating status of other coils, such as solenoids or transformers, that have a voltage source that intermittently sends current to the coil.

  This disclosure has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and changes may be made thereto without departing from the broader spirit and scope of the disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

FIG. 2 shows an exemplary circuit for controlling the operation of a fuel injector. It is a figure which shows the waveform of the voltage of the injector coil with respect to the ground displayed with the big scale on the oscilloscope. FIG. 3 is a diagram of the injector voltage that is the same as that shown in FIG. 2 but shown on a fine scale. 4a and 4b are diagrams of injector voltage waveforms obtained from two injectors, one having a normal resistance and the other having a higher resistance than that of a normal injector. FIGS. 5a and 5b are diagrams of injector voltage waveforms obtained from two injectors, one having normal resistance and the other having lower resistance than that of a normal injector. FIG. 2 illustrates an example tester used to perform fuel injector diagnostics. Fig. 6 is a flow chart illustrating exemplary diagnostic steps. 6 is a flow chart illustrating the steps of another example of diagnosing an injector coil using an exemplary tester.

Claims (18)

An inspection device for diagnosing a fuel injector having an injector coil that is charged by a power source during an energization period,
A data port for receiving signals;
A data storage device;
A data processing unit coupled to the data port and the data storage device,
The data storage device has instructions, and the instructions are sent to the tester when the instructions are executed by the data processing unit.
Accessing a first signal representative of a first energization state of the injector coil during an energization period;
Accessing a second signal representative of a second energization state of the injector coil during the energization period; and
An inspection device for performing a machine-implemented step of determining a first operating state of the injector based on a level difference between the first signal and the second signal.   The instruction further causes the tester to determine a second operating condition of the injector based on a level of at least one of the first signal and the second signal when executing the instruction by the data processing unit. The inspection device according to 1.   The inspector of claim 1, wherein the first operating condition indicates whether the injector coil has a resistance value that is higher than an acceptable value.   The inspector according to claim 2, wherein the instruction causes the inspector to determine whether the level is lower than a predetermined value when the instruction is executed by the data processing unit.   The inspector according to claim 1, wherein the step of determining the first operating state of the injector determines whether or not a level difference between the first signal and the second signal falls within a predetermined range.   6. The inspector of claim 5, wherein the first and second signals represent injector coil voltages.   The instruction indicates to the inspector that, when executed, the injector coil has a high resistance in response to the level difference between the first energized state and the second energized state not being within a predetermined range. The inspection device according to claim 6.   The inspector of claim 4, wherein the first and second signals represent injector coil voltages.   9. The inspector of claim 8, wherein the instruction causes the inspector to indicate that the injector coil is short-circuited when executed in response to the level being greater than a predetermined value. A machine readable medium having instructions for controlling the operation of an inspector for diagnosing a fuel injector having an injector coil that is supplied with current during an energization period, the inspector comprising energizing the injector coil A data port configured to receive a signal representative of a state; a data retrieval device for reading data from the machine readable medium; and a data processing unit coupled to the data port and the data storage device, the instructions comprising: When executed by the processing unit,
Accessing a first signal representative of a first energization state of the injector coil during an energization period;
Accessing a second signal representative of a second energization state of the injector coil during the energization period; and
A machine-readable medium that causes a machine-implemented step of determining a first operating condition of an injector based on a level difference between a first signal and a second signal. An inspection device for diagnosing a fuel injector having an injector coil that is charged during an energization period,
A data port for receiving signals;
A data storage device;
A data processing unit coupled to the data port and the data storage device,
The data storage device has instructions, and the instructions are sent to the tester when the instructions are executed by the data processing unit.
Accessing a first signal representative of a first energization state of the injector coil during an energization period;
Accessing a second signal representative of a second energization state of the injector coil during the energization period;
Determining whether the fuel injector has a lower resistance than acceptable based on the levels of the first and second signals; and
A test that causes a machine-implemented step to determine whether the fuel injector has a greater resistance than is acceptable based on the level difference between the first signal and the second signal. vessel. An inspection device for diagnosing a fuel injector having an injector coil that is charged during an energization period,
A data port for receiving signals;
A data storage device;
A data processing unit coupled to the data port and the data storage device,
The data storage device has instructions, and the instructions are sent to the tester when the instructions are executed by the data processing unit.
Accessing a first signal representative of a first injector voltage during an energization period;
Accessing a second signal representative of a second injector voltage during energization;
Determining whether the fuel injector has a lower resistance than acceptable based on a level of at least one of the first and second injector voltages; and
A machine-implemented step of determining whether the fuel injector has a greater resistance than acceptable based on a level difference between the first injector voltage and the second injector voltage; Inspector to perform. An inspection device for diagnosing a coil to which electric current is intermittently supplied,
A data port for receiving signals;
A data processing unit coupled to the data port;
The data processing unit
Accessing a first signal representative of a first coil voltage when current is supplied to the coil;
Accessing a second signal representative of a second coil voltage as current is supplied to the coil; and
An inspector configured to perform a machine-implemented step of determining a first operating state of the coil based on a difference between the first coil voltage and the second coil voltage. An inspection device for diagnosing a coil to which electric current is intermittently supplied,
A data port for receiving signals;
A data processing unit coupled to the data port;
The data processing unit
Accessing a sample signal representative of the coil voltage as current is supplied to the coil;
Accessing a threshold; and
An inspector configured to perform a machine-implemented step of determining whether a coil has an abnormally low resistance based on a sample signal and a threshold. An inspection device for diagnosing a fuel injector having an injector coil to which electric current is intermittently supplied,
Signal receiving means for receiving a signal;
Data processing means for processing data received by the signal receiving means,
Data processing means
Accessing a first signal representative of a first injector voltage when current is supplied to the injector coil;
Accessing a second signal representative of a second injector voltage as current is supplied to the injector coil; and
It is configured to perform a machine-implemented step of determining whether the fuel injector has an abnormally high resistance based on the difference between the first injector voltage and the second injector voltage. The inspection device.   The data processing means is further configured to perform the machine-implemented step of determining whether the fuel injector has an abnormally low resistance based on the injector voltage at which current is supplied to the injector coil. The inspector according to claim 15, wherein An inspection device for diagnosing a coil to which electric current is intermittently supplied,
Means for receiving the signal;
Data processing means coupled to the data port;
Data processing means
Accessing a sample signal representative of the coil voltage as current is supplied to the coil;
Accessing a threshold; and
An inspector configured to perform a machine-implemented step of determining whether a coil has an abnormally low resistance based on a sample signal and a threshold. A method for diagnosing a fuel injector having an injector coil that is supplied with current during an energization period, comprising:
Accessing a first signal representative of a first energization state of the injector coil during an energization period;
Accessing a second signal representative of a second energization state of the injector coil during the energization period; and
A method comprising a machine-implemented step of determining a first operating condition of an injector based on a level difference between a first signal and a second signal.

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