Circuit Description
The engine control module (ECM)/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 ECM/PCM applies a voltage to the voltage regulator. When the ECM/PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the ECM/PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.
The ECM/PCM monitors the state of the generator turn on signal circuit. With the engine running, the ECM/PCM should detect a high generator turn on signal circuit, or when the charging system malfunctions. If the ECM/PCM detects a low generator turn on signal circuit DTC P0621 will set. When the DTC sets, the ECM/PCM will send a class 2 serial data message to the instrument panel cluster (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 ECM/PCM detects a high signal voltage on the generator turn on signal circuit for at least 5 seconds.
During the RUN test, the ECM/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 ECM/PCM sends a class 2 message to the IPC to illuminate the charge indicator. |
| • | The ECM/PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The ECM/PCM will store the conditions present when the DTC set as Fail Records data only. |
| • | The Service Vehicle Soon (SVS) light may be illuminated. |
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 |
|---|---|---|---|---|
Connector End View Reference: Engine Electrical Connector End Views , Engine Control Module Connector End Views for the engine 2.2L (L61), or Powertrain Control Module Connector End Views for the 3.5L (L66) engine | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC P0621 has passed this ignition cycle? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 |
Does the scan tool indicate Disabled then Enabled or Inactive then Active 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 . 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 . 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 . 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 ECM/PCM. Refer to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 |
9 |
Important: The replacement ECM/PCM must be programmed. Replace the ECM/PCM. Refer to Control Module References 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 |
