Circuit Description
The powertrain control module (PCM) uses the generator turn on signal circuit to control the generator. A high side driver within the PCM allows the PCM to turn the generator ON and OFF. When Generator operation is desired, the PCM sends a 5 volt signal to the voltage regulator via the generator turn on signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the Generator is enabled by the PCM, the voltage regulator controls generator output independently of the PCM. Under certain operating conditions, the PCM can turn Off the generator by turning Off the 5 volt signal on the generator turn on signal circuit. The PCM has fault detection circuitry which monitors the state of the generator turn on signal circuit. If the fault detection circuit senses a voltage other than what is expected, this DTC will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the PCM to set the DTC.
Conditions for Running the DTC
| • | The ignition is on. |
| • | System voltage between 9.0 and 18.0 volts. |
Conditions for Setting the DTC
| • | An improper voltage level has been detected on the alternator lamp driver circuit. |
| • | Above conditions for at least 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Starting and Charging Schematics | |||
1 | Did you perform the Engine Electrical Diagnostic System Check? | Go to Step 2 | |
2 |
Does the parameter indicate voltage as being 10V or greater? | Go to Step 4 | Go to Step 3 |
3 | Test the generator turn on signal circuit for a high resistance or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 5 |
4 | Inspect for poor connections at the harness connector of the generator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
5 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 |
6 | Replace the generator. Refer to Generator Replacement in Engine Electrical. | Go to Step 8 | -- |
7 |
Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Programming in Engine Controls-5.7L. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-5.7L. Is the action complete? | Go to Step 8 | |
8 |
Does the DTC reset? | Go to Step 2 | System OK |
