For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC B1420: Device Voltage Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ | B1420 | B1420 | -- | --
Ground | -- | B1420 | -- | --

### Typical Scan Tool Data

#### Battery Voltage - BCM

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Ignition ON, engine OFF. Parameter Normal Value: 12.60 Volts
B+ | 0.00 Volts | 0.00 Volts | 12.60 Volts

### Circuit/System Description

The body control module (BCM) monitors the battery voltage on the battery voltage signal circuit. Damage to components, and incorrect data may occur when the voltage is out of range.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

Battery voltage is outside the range of 9-16 V for 1 second.

### Action Taken When the DTC Sets

• | The BCM will disable its outputs when a high voltage condition is detected.

• | The BCM inhibits the setting of other DTCs.

### Conditions for Clearing the DTC

The DTC passes when the malfunction is no longer present.

### Diagnostic Aids

• | Overcharging with a battery charger and jump starting may set this DTC.

• | A high or low voltage value in multiple modules indicates a concern in the charging system.

### Reference Information

#### Schematic Reference

Body Control System Schematics

#### Connector End View Reference

Engine Electrical Connector End Views

#### Description and Operation

Charging System Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

1. Engine running, accessories OFF, measure and record the voltage at the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 V.

⇒ | If not within the specified range, refer to Charging System Test.

2. Observe the scan tool BCM Battery Voltage parameter. The reading should be between 12.6 and 15.0 V.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connectors at the BCM.
2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 Ω between the ground circuit terminal B3 X1 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.

• | Terminal A7 X1

• | Terminal B5 X1

• | Terminal B8 X1

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. If all circuits test normal, replace the BCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the BCM replacement, setup, and programming.