For 1990-2009 cars only
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 CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Battery Positive Voltage Circuit | B1420 | B1420 | -- | -- |
Ground Circuit | B1420 |
Circuit/System Description
The body control module (BCM) monitors the battery voltage through the battery voltage signal circuit. If the BCM senses that battery voltage is outside of its normal range, DTC B1420 will set. Damage to components, and incorrect data may occur when the voltage is out of range.
Conditions for Running the DTC
| • | The voltage supplied to the BCM are in the range of 7-26 volts. |
| • | The ignition is ON. |
| • | The engine is running. |
Conditions for Setting the DTC
| • | The BCM senses a battery voltage above or below the specified range of 9-16 volts. |
| • | The above condition lasts for at 1 second. |
Action Taken When the DTC Sets
| • | The BCM will disable all its outputs when a high voltage condition is detected. |
| • | The setting of this DTC inhibits the setting of other DTCs. |
Conditions for Clearing the DTC
The DTC clears when the system voltage returns to a normal range.
Diagnostic Aids
| • | A high or low voltage DTC set in multiple modules indicates a concern in the charging system. |
| • | A possible cause of this DTC could be overcharging with a battery charger or jump starting. |
| • | A high or low voltage value in multiple modules indicates a concern in the charging system. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Engine running measure and record the voltage at the battery terminals.
- Verify that the battery voltage is 12.5-15.5 volts.
- Engine running, observe the scan tool BCM Battery Positive Voltage parameter.
- Verify that the scan tool displays a value that is within 2 volts of the battery terminal voltage.
| ⇒ | If the battery voltage is not within the specified range, refer to Charging System Test . |
Circuit/System Testing
- Ignition OFF, disconnect the harness connectors at the BCM.
- Ignition OFF, verify that there is less than 1.0 ohm between the ground circuits X1 terminals 17-19-20 and X2 terminal 50 to ground.
- Ignition ON, verify a test lamp illuminates between the battery positive voltage circuits X1 terminals 46-50-51-52 and X2 terminal 49 to ground.
- If all the circuits test normal, replace the BCM.
| ⇒ | If greater than the specified value, test the ground circuits for an open/high resistance. |
| ⇒ | If the test lamp did not illuminate, test the battery positive voltage circuits for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for BCM replacement, setup, and programming
