GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2009 🢒 LaCrosse 🢒 Engine 🢒 Engine Electrical 🢒 DTC B1420

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 Descriptors

DTC B1420 00: Device Voltage Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

B+ / IGN

B1420 00

B1420 00

--

--

Ground

--

B1420 00

--

--

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 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.

Reference Information

Schematic Reference

Body Control System Schematics

Connector End View Reference

Component 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

Control Module References for scan tool information

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.

Circuit/System Verification
  1. Engine running measure and record the voltage at the battery terminals. Verify that the battery voltage is 12.5-15.5 volts.
    2. ⇒If the battery voltage is not within the specified range, refer to Charging System Test
  2. 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.

Circuit/System Testing
  1. Ignition OFF. Disconnect the harness connectors at the BCM.
  2. Ignition OFF, test for less than 5.0 ohms between the BCM ground circuit terminals listed below and ground.
    3. • Terminal 17 X1
    • Terminal 19 X1
    • Terminal 20 X1
    • Terminal 50 X2
    ⇒If greater than the specified value, test the ground circuits for an open/high resistance.
  3. Ignition ON, verify a test lamp between the B+ / IGN circuits terminals listed below and ground.
    4. • Terminal 46 X1
    • Terminal 50 X1
    • Terminal 51 X1
    • Terminal 52 X1
    • Terminal 3 X1
    • Terminal 22 X1
    • Terminal 23 X1
    ⇒If the test lamp does not illuminate , test the B+ / IGN circuits for a short to ground or an open/high resistance.
  4. If all the circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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