CHART A5 (2 of 2) - INJECTOR SYSTEM DIAGNOSIS

Fig 1: Chart A5, Injector System Diagnosis Schematic

NOTE: The injector circuit test should only be performed when driveability condition is present or when one injector is visually verified to be inoperative. For the injector circuit test to result in a positive diagnosis of an injector circuit fault, the voltage measurements requested by CHART A5 must be taken with injector fault present.

The fuel injectors are powered through the 3-amp injector fuses. The ECM turns on injectors by applying a ground to ECM connector terminals D15 and D16 (injector drive circuits). The ECM grounds injector drive circuits to turn on fuel injectors to supply fuel to engine. ECM data parameter ED06 (injector pulse width), reflects the time in milliseconds that ECM turns on ground to injectors for each injector pulse.

When measuring voltages between ECM connector terminals D15 and D16, the voltmeter should read "00.0" volts if ECM is able to control both fuel injectors to provide equal amounts of fuel. If one injector loses power from fuse or loses ground from ECM, the voltage measured between terminals D15 and D16 will not be zero. This reflects unequal voltage drops across injector coils. The voltage reading obtained when an injector fault is present can be used to diagnose injector open to voltage, injector open to ECM, injector coil open, or ECM unable to ground injector drive circuits.

To obtain an accurate and useable voltage reading, Digital Volt/Ohmmeter (DVOM J34029-A) must be used. The DVOM must be connected as directed by CHART A5 (Cont.) and must be set on 200-volt (DC) scale.

NOTE: Test numbers refer to test numbers on diagnostic chart.

If DVOM reads "00.0" volts, both injectors are being powered through fuses and grounded by ECM an equal amount. No fault exists at this time.
If DVOM reads "00.2" or "02.0" volts and voltage polarity is negative, injector "B" is inoperative. Terminal D15 of Red ECM connector is not grounding injector drive circuit No. 468. The cause is an ECM connector fault or an ECM fault. If voltage polarity is positive, injector "A" is inoperative. Terminal D16 of Red ECM connector is not grounding injector drive circuit No. 467. The cause is an ECM connector fault or an ECM fault.
If DVOM reads greater than "2.0" volts, the fault is an open circuit from one of the 3A injector fuses to ECM. A negative voltage polarity means that an open exists between injector "A" voltage supply and ECM. Check circuit No. 481, injector coil of injector connected to Blue and Red wires and circuit No. 467, for open or short circuits to ground. A positive voltage polarity means that an open exists between injector "B" voltage supply and ECM. Check circuit No. 482, injector coil of injector connected to Green and White wires, circuit No. 468 for open or short circuits to ground.

Fig 2: Flow Chart A5, Injector System Diagnosis

Fig 3: Flow Chart A5, Injector System Diagnosis