Circuit Description
The powertrain control module (PCM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the PCM applies a voltage to the voltage regulator. When the PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.
The PCM monitors the state of the generator turn on signal circuit. With the engine running, the PCM should detect a high generator turn on signal circuit, or when the charging system malfunctions. If the PCM detects a low generator turn on signal circuit DTC P0621 will set. When the DTC sets, the PCM will send a serial data message to the IPC to illuminate the charge indicator.
DTC Descriptor
This diagnostic procedure supports the following DTC: DTC P0621 Generator L-Terminal Circuit
Conditions for Running the DTC
Key ON Test
| • | The key is in the ON position for 5 seconds. |
| • | The engine is OFF. |
Engine Run Test
| • | The engine is running. |
| • | The engine speed is less than 3,000 RPM. |
Conditions for Setting the DTC
During key ON test, the PCM detects a high signal voltage on the generator turn on signal circuit for at least 5 seconds.
During the RUN test, the PCM detects a low signal voltage on the generator turn on signal circuit for at least 10 seconds.
Action Taken When the DTC Sets
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store the conditions present when the DTC set as Fail Records data only. |
Conditions for Clearing the MIL/DTC
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool Clear DTC Information function. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End Views: Engine Electrical Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the scan tool indicate that DTC P0621 has passed this ignition cycle? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
3 |
Does the scan tool indicate a change in voltage each time the Generator L - Terminal is commanded Off and On? | -- | Go to Step 6 | Go to Step 4 |
4 |
Is the voltage within the specified range. | 4.5-5.5 V | Go to Step 7 | Go to Step 5 |
5 | Test the generator turn on signal circuit for a short, high resistance or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
6 | Test the generator battery voltage output 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 10 | Go to Charging System Test |
7 | Inspect for poor connections at the harness connector of the generator. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Charging System Test |
8 | Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the scan tool indicate that DTC P0621 failed? | -- | Go to Step 3 | System OK |
