GM Service Manual Online
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

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Driver Window Switch B+

1

1

--

--

Driver Door Module B+

1

1

--

--

Passenger Window Switch Up Signal

B3170

2

2

--

Passenger Window Switch Down Signal

B3175

2

2

--

Passenger Window Switch Express Down Signal

B3280

2

2

--

Driver Door Module Ground

--

B1420

1

--

Driver Window Switch Ground

--

1

1

--

Passenger Door Module Ground

--

B1420

2

--

Passenger Window Switch Ground

--

2

2

--

1. Driver Window Malfunction

2. Passenger Window Malfunction

Circuit/System Description

The driver door module (DDM) and passenger door module (PDM) check for proper system voltage of 9-16 volts at least once every 20 milliseconds.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

While attempting a power window OPEN or CLOSE command, the DDM and/or PDM detects the voltage is below 9 volts or above 15.9 volts for greater than 5 seconds.

Action Taken When the DTC Sets

The power windows will be inoperative

Conditions for Clearing the DTC

    • The DTC will be current for as long as the fault is present.
    • When the fault is no longer present, the DTC will be a history DTC.
    • A history DTC will clear after 50 ignition cycles.

Reference Information

Schematic Reference

Moveable Window Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Windows 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

Circuit/System Verification

Ignition ON, observe the scan tool Battery Voltage Signal parameter while commanding the power windows to OPEN and CLOSE by using the driver window switch. The parameter should be between 9.6-13.6 volts.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate door module.
  2. Ignition ON, test for 9.6-13.6 volts between the B+ circuit terminal 20 and ground.
  3. If less than the specified range, test the B+ circuit for a an open/high resistance. If the circuit tests normal, replace the door module.
    If the circuit tests normal and the system voltage is less than or greater than the specified range, refer to Charging System Test .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for DDM or PDM replacement, setup, and programming