Diagnosis
Use the following diagnostic table to diagnose the generator F and L circuit.
Use the following scan tool parameters when diagnosing the Powertrain Control Module (PCM) controlled generator.
Generator PWM - Range 0-100 Percent: The generator F terminal is a pulse width modulated (PWM) duty cycle or load input to the PCM from the generator. As the generator load increases, the PCM can sense the change and adjust the idle speed accordingly.Generator L Terminal - Range Inactive/Active: The generator L terminal indicates whether the PCM is allowing the generator to operate. The PCM can disable the generator under certain conditions in order to ease starting. Active indicates that the PCM is allowing generator operation, while inactive indicates that the PCM is not allowing generator operation.
Circuit Description
The generator communicates to the Powertrain Control Module (PCM) over two lines, the L or lamp circuit and the F or Field circuit. The PCM uses the L circuit to monitor faults in the charging system. The F circuit is used by the PCM to monitor the duty cycle or load of the generator. The PCM will adjust the idle speed according to the generator load.
Diagnostic Aids
| • | A Body Control Module (BCM) DTC may set when a generator malfunction is present. Check for any BCM DTCs and make any necessary repairs. |
| • | When the engine is not running, the generator duty cycle will be displayed above 5%. If the generator duty cycle reads 0%, then the field circuit is either open or shorted to ground. |
| • | An Intermittent problem may be caused by the following conditions:. |
| • | Poor electrical connection |
| • | Rubbed through wire insulation |
| • | Wire that is broken inside the insulation |
| • | Any circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for the following items: |
| - | Improper mating |
| - | Broken locks |
| - | Poor terminal to wiring connections |
| - | Physical damage to the wiring harness |
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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If the volts telltale lamp is not operating, the IPC or the BCM is malfunctioning.
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If no malfunctions are present at this point, refer to Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
2 |
Was a DTC P0562, P0563, U1000 or U1064 set? | -- | Go to applicable DTC table | |
Turn ON the ignition switch leaving the engine OFF. Is the volts telltale lamp on the IPC illuminated? | -- | |||
4 |
Did the volts telltale lamp on the IPC turn OFF? | -- | ||
5 | Check if any Body Control Module (BCM) DTCs are set. Are any BCM DTCs set? | -- | Go to Diagnostic System Check - Body Control System in Body Control Systems. | Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gauges and Co. |
Operate the vehicle within the conditions under which the original symptom was observed. Does the system now operate properly? | -- | System OK |
