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 Descriptors

DTC B1548 0A: Seat Back Rotation Position Sensor Circuit

DTC B1825 0A: Seat Recline Position Sensor Circuit

DTC B2375 0A: Seat Assembly Horizontal Position Sensor Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Folding Seat Horizontal Position Sensor Signal

B2375 0A

B2375 0A

B2375 0A

--

Folding Seat Recline Position Sensor Signal

B1825 0A

B1825 0A

B1825 0A

--

Folding Seat Rotation Position Sensor Signal

B1548 0A

B1548 0A

B1548 0A

--

Folding Seat Horizontal Motor Forward Control

B1770 0B

B2375 0A or 1

--

--

Folding Seat Horizontal Motor Rearward Control

B1770 0B

B2375 0A or 1

--

--

Folding Seat Recline Motor Forward Control

B1785 0B

B1825 0A or 1

--

--

Folding Seat Recline Motor Rearward Control

B1785 0B

B1825 0A or 1

--

--

Folding Seat Rotation Motor Forward Control

B1547 0B

B1548 0A or 1

--

--

Folding Seat Rotation Motor Rearward Control

B1547 0B

B1548 0A or 1

--

--

Low Reference

--

B1548 0A, B1825 0A, B2375 0A

--

--

1. Power Third Row Seat Inoperative

Circuit/System Description

The rear seat module (RSM) monitors the position the rear folding seat motors by using hall effect position sensors which are an internal part of each motor. The RSM supplies each sensor with a 12-volt reference signal circuit and a low reference circuit. During seat operation, while the motor is active, each sensor provides the RSM with a single feedback pulse through the respective signal circuits for every rotation of the motor shaft. The RSM counts the feedback pulses from each sensor to determine seat position and end of travel limits for each of the seat motors.

Conditions for Running the DTC

    • DTC B1325 must not be present.
    • Battery voltage must be between 9-16 volts.
    • The seat adjuster motor must be active.

Conditions for Setting the DTC

The RSM does not detect position sensor movement or pulse signals while the adjuster motor is active. The following conditions will set this DTC:

    • An open, short to ground, or short to battery voltage in the position sensor signal circuit.
    • An open in the position senor low reference circuit.
    • An open in one of the seat motor control circuits.

Action Taken When the DTC Sets

    • Current and history codes are set.
    • If the seat is moving when this condition occurs, the operation will be aborted.
    • While this condition exists all switch inputs will be ignored.

Conditions for Clearing the DTC

The RSM will clear the current DTC whenever a stow switch is activated and the RSM receives pulse signals from the position sensor while the motor is active.

Reference Information

Schematic Reference

Rear Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Seats 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

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the appropriate seat adjuster motor for which the DTC set.
  2. Ignition OFF, test for less than 2 ohms between the low reference circuit terminal 3 and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the RSM.
  4. Ignition ON, test for 4.5-12 volts between the signal circuit terminal 4 and ground.
  5. If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the RSM.
    If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the RSM.
  6. Connect a test lamp between control circuits terminal 1 and terminal 2.
  7. Command the appropriate motor to the Forward and Rearward directions with a scan tool. The test lamp should momentarily turn ON when commanding the Forward and Rearward states.
  8. If the test lamp remains OFF during either of the commands, test for a short to ground or an open/high resistance on either control circuit. If the circuits test normal, replace the RSM.
  9. If all circuits test normal, test or replace the motor/position sensor.

Repair Instructions

Important: After performing this diagnostic test and electrical or component repairs have been completed, the folding seat will be in an unknown state and out of calibration with the RSM. The RSM must be calibrated before the folding seat system will operate. Refer to Power Folding Seat Calibration .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Rear Seat Number 2 Back Pivot Actuator Motor Replacement - Cushion
    •  Rear Seat Number 2 Back Pivot Actuator Motor Replacement - Back Cushion
    •  Rear Seat Number 2 Back Recliner Actuator Motor Replacement
    •  Control Module References for RSM replacement, setup, and programming