For 1990-2009 cars

### Circuit Description

The generator battery control module controls the generator through the generator turn on signal circuit. The signal is a 5-volt 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 turn on signal circuit is in the 0-5 percent range, pulled low to ground or open then DTC B1487 will set.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1487 Generator L-Terminal Circuit Low

### Conditions for Running the DTC

• | The engine speed is greater than 450 RPM.

• | This diagnostic shall be run every 100 ms.

### Conditions for Setting the DTC

The generator turn on 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 Charging System Failure and commands ON the Battery indicator.

### Conditions for Clearing the DTC

• | The generator turn on signal circuit input is from 1-99 percent duty cycle, greater than 0 volts.

• | 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 L-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 Charging System Failure 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. Turn ON the engine.
2. With a DMM test the generator turn on signal circuit of the generator battery control module.

Is the DMM reading equal to the specified value?

0 V

Go to Step 4

Go to Step 3

3 | 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 6 | Go to Step 5
4 | Repair the short to ground of the generator turn on signal circuit. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 5
5 | Replace the generator battery control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 6 | --
6 |

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