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 B1826: Driver Recline Sensor Performance

DTC B2356: Driver Front Vertical Sensor Performance

DTC B2366: Driver Rear Vertical Sensor Performance

DTC B2376: Driver Seat Assembly Horizontal Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5-Volt Reference - Seat Position Sensors

B1825, B2355, B2365, B2375

B1825, B2355, B2365, B2375

B1825, B2355, B2365, B2375

B1826, B2356, B2366, B2376

Front Vertical Position Sensor Signal

B2355

B2355

B2355

--

Horizontal Position Sensor Signal

B2375

B2375

B2375

--

Recline Position Sensor Signal

B1825

B1825

B1825

--

Rear Vertical Position Sensor Signal

B2365

B2365

B2365

--

Memory Seat/Mirror Sensor Low Reference

--

B1825, B2355, B2365, B2375

--

B1826, B2356, B2366, B2376

Circuit/System Description

The position sensor that sets this diagnostic trouble code (DTC) is either attached to the seat directional motor drive cable or directly to the motor it monitors. It receives a 5-volt reference and low reference from the memory seat module (MSM). The sensor sends a voltage signal that varies with the movement of the seat through the signal circuit to the MSM. Then based on this voltage signal, the MSM determines the position of the seat.

Conditions for Running the DTC

    • DTC B1327 must not be present.
    • Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

This DTC will set, if the MSM is controlling a motor in one direction and it's position sensor is tracking the motor in the opposite direction. The sensor is either mounted or wired incorrectly, or the polarity of the motor control circuits are reversed.

Actions Taken When the DTC Sets

The motor associated with the fault will be disabled for memory functions.

Conditions for Clearing the DTCs

    • The condition responsible for setting the DTC no longer exists.
    • A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred.

Diagnostic Aids

The memory seat module is also referred to as the Driver Position Module in certain scan tool menus.

Reference Information

Schematic Reference

Driver Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Memory Seats 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 Testing

B1826

  1. Ignition OFF, disconnect the X1 harness connector at the driver seat recline motor.
  2. Verify that the control circuits listed below are in the correct harness connector cavities:
  3. • Recline forward terminal A
    • Recline rearward terminal B
    If the control circuits are not in the correct cavities, make the appropriate changes.
  4. Disconnect the X2 harness connector at the driver seat recline motor.
  5. Verify that the 5-volt reference and low reference circuits listed below are in the correct harness connector cavities:
  6. • 5-volt reference terminal A
    • Low reference terminal D
    If the 5-volt reference and low reference circuits are not in the correct cavities, make the appropriate changes.
  7. If all circuits test normal, replace the MSM.

B2356, B2366, B2376

  1. Ignition OFF, disconnect the X1 harness connector at the driver seat adjuster motor assembly.
  2. Verify that the appropriate control circuits listed below are in the correct harness connector cavities:
  3. • Front vertical motor up control terminal C
    • Front vertical motor down control terminal D
    • Rear vertical motor up control terminal E
    • Rear vertical motor down control terminal F
    • Seat horizontal motor forward control terminal A
    • Seat horizontal motor rearward control terminal B
    If the control circuits are not in the correct cavities, make the appropriate changes.
  4. Disconnect the appropriate X2, X3, X4 harness connector at the driver seat adjuster motor assembly.
  5. Verify that the appropriate 5-volt reference and low reference circuits listed below are in the correct harness connector cavities:
  6. • Front vertical sensor 5-volt reference terminal C
    • Front vertical sensor low reference terminal A
    • Rear vertical sensor 5-volt reference terminal C
    • Rear vertical sensor low reference terminal A
    • Seat horizontal sensor 5-volt reference terminal A
    • Seat horizontal sensor low reference terminal C
    If the 5-volt reference and low reference circuits are not in the correct cavities, make the appropriate changes.
  7. If all circuits test normal, replace the MSM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for MSM replacement, setup, and programming