For 1990-2009 cars

### Circuit Description

The generator battery control module monitors the battery voltage for precision electrical power management. The generator battery control module monitors both the battery sense positive voltage circuit and the battery sense negative, ground, circuit to precisely determine system voltage. If there is a difference between the less precise battery voltage, battery positive voltage circuit and ground circuit, and the more precise battery sense voltage of 1 volt or more for 10 seconds, then DTC B1390 will set.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1390 Device Voltage Reference Input 1 Circuit

### Conditions for Running the DTC

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

• | This diagnostic shall be run every 100 ms.

### Conditions for Setting the DTC

The difference between the low precision battery voltage circuit reading and the high precision battery voltage sense circuit reading is greater than or equal to 1 volt for 10 seconds.

### Action Taken When the DTC Sets

The generator battery control module will request the driver information center (DIC) message of the Service Charging System. The battery tell-tale is not turned ON.

The generator battery control module uses the less accurate battery positive voltage circuit for voltage readings.

### Conditions for Clearing the DTC

• | During the current ignition cycle, the difference between the less precision battery positive voltage circuit reading and the high precision battery voltage sense circuit reading is less than 1 volt.

• | 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:

• | Check the Batt + voltage and Batt + sense voltage wires for an open or short low condition.

• | Check the Batt - ground and Batt - sense ground wires for an open or short high 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.

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 | With a DMM, measure the voltage between both the battery positive voltage circuits of the generator battery control module and a good ground. Compare the reading between circuits. Is the DMM reading above the specified value? | 1 V | Go to Step 4 | Go to Step 3
3 | With a DMM connected to a good battery positive source, test both the ground circuits of the generator battery control module. Compare the reading between circuits. Is the DMM reading above the specified value? | 1 V | Go to Step 6 | 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 8 | Go to Step 5
5 | Repair the open or high resistance in the affected battery positive voltage circuit. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7
6 | Repair the open or high resistance in the affected generator battery control module ground circuit. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7
7 | Replace the generator battery control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 8 | --
8 |

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