For 1990-2009 cars

### Circuit Description

The engine control module (ECM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the ECM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the ECM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The ECM monitors the state of the generator turn on signal circuit. The ECM should detect a low generator turn on signal circuit voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. If the ECM detects a high generator turn on signal circuit voltage, DTC P2501 will set.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2501 Generator L-Terminal Circuit High Voltage

### Conditions for Running the DTC

• | No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs are set.

• | The ignition is in the ON position.

• | The engine is not running.

### Conditions for Setting the DTC

The ECM detects a high signal voltage on the generator turn on signal circuit for at least 5 seconds.

### Action Taken When the DTC Sets

• | The ECM will not illuminate the malfunction indicator lamp (MIL).

• | The ECM will store the conditions present when the DTC set as Fail Records data only.

• | The ECM will send a class 2 serial data message to the instrument panel cluster (IPC) and driver information center (DIC) to illuminate the charge indicator or display a charging message.

### Conditions for Clearing the MIL/DTC

• | The conditions for setting DTC P2501 are not present.

• | 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 View Reference: Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn OFF the ignition.
2. Disconnect the generator harness connector.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage between the generator turn on signal circuit of the generator harness connector and a good ground.

Is the voltage within the specified range?

3.5-5.5 V

Go to Step 3

Go to Step 4

3 | Test the generator turn on signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 5
4 | 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 7 | Go to Charging System Test
5 | Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Connector Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6
6 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | --
7 |

1. Review and record the scan tool Fail Records data.
2. Use the scan tool in order to clear the DTC.
3. Operate the vehicle within the conditions for running DTC.
4. Using the scan tool, observe the specific DTC information for DTC P2501 until the test runs.

Does the scan tool indicate that DTC P2501 failed?

--

Go to Step 2

System OK