For 1990-2009 cars

### Circuit Description

The generator battery control module monitors the generator through the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. If the generator field duty cycle signal circuit is in the 0-5 percent range or pulled low to ground, then DTC B1492 will set.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1492 Generator F-Terminal Circuit Low

### Conditions for Running the DTC

• | Vehicle in RUN mode and Engine Run Flag is True.

• | The engine speed is less that 1,000 RPM.

• | DTC B1487 or B1488 is not set as a current DTC.

• | This diagnostic shall be run every 100 ms.

### Conditions for Setting the DTC

The generator field duty cycle signal circuit is less than or equal to 5 percent duty cycle for more than 120 seconds.

### Action Taken When the DTC Sets

The generator battery control module will request the driver information center (DIC) message of Service Charging System and commands ON the Battery indicator.

### Conditions for Clearing the DTC

• | The generator field duty cycle signal circuit input is greater than 5 percent duty cycle.

• | Clear the DTC with a scan tool.

### Diagnostic Aids

Important: You must cycle the ignition after clearing the DTC to turn OFF the DIC message of Service Charging System.

Recommended Action:

• | Correct F-Term short low condition.

• | Clear the codes.

• | Cycle the ignition.

Important: You must cycle the ignition after clearing the DTC to turn OFF the DIC message of Service Charging System and turn OFF the battery indicator.

If a fault condition persists, replace the module.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Start engine and idle.
2. With a scan tool, observe the Generator F-Terminal Signal parameter in the powertrain control module (PCM) data display.

Is the Generator F-Terminal Signal data less than the specified value?

5%

Go to Step 3

Testing for Intermittent Conditions and Poor Connections

3 | Disconnect the generator battery control module harness connector Is the Generator F-Terminal Signal parameter still less than the specified value? | 5% | Go to Step 5 | Go to Step 4
4 | Inspect for poor connections at the harness connector of the generator battery control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6
5 | Repair the short to ground of the generator field duty cycle control circuit. Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6
6 | Replace the generator battery control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | --
7 |

1. Use the scan tool in order to clear the DTC.
2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK