Buick Regal: DTC B1405, B1825, B2355, B2365, or B2375 (Passenger Seat)

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 B1405

Control Module Voltage Reference Output 2 Circuit

DTC B1825

Seat Recline Position Sensor Circuit

DTC B2355

Seat Front Vertical Position Sensor Circuit

DTC B2365

Seat Rear Vertical Position Sensor Circuit

DTC B2375

Seat Assembly Horizontal Position Sensor Circuit

For symptom byte information refer to Symptom Byte List.

Diagnostic Fault Information

Circuit Description

The seat memory control module monitors the position of the seat motors by using hall effect position sensors which are an internal part of each motor. The module supplies each sensor with a 12 V reference circuit only when any seat motor is active, and a low side signal circuit. During seat motor operation, the hall effect position sensor provides a determined number of pulse signals for every revolution of the motor shaft. The scan tool displays these pulse signals as counts that range from 0 - 65, 535. The module counts the feedback pulses from each sensor to determine seat position and end of travel limits for each of the seat motors. High scan tool count values indicate forward or upward seat positions while low count values indicate rearward or downward seat positions.

Conditions for Running the DTC

• Any seat motor must be active.
• DTC B1325 must not be present.
• Module battery voltage must be between 9 - 16 V.

Conditions for Setting the DTC

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

B1405 02

The seat memory control module detects a short to ground or an open on the 12 V reference circuit.

B1825 01, B2355 01, B2365 01, or B2375 01

The seat memory control module detects a voltage greater than 5 V on the sensor signal circuit.

B1825 06, B2355 06, B2365 06, or B2375 06

The seat memory control module detects a short to ground or an open on the sensor signal circuit.

Action Taken When the DTC Sets

• With a short to ground or an open circuit, the seat memory control module disables the memory recall and easy exit/entry action commands of the motor monitored by the sensor. The motor will respond to manual position commands.
• With a short to battery voltage, the seat memory control module disables the memory recall and easy exit/entry action commands for all four seat motors. The motors will respond to manual position commands.

Conditions for Clearing the DTC

• The current DTC clears when the fault is no longer present and the power mode changes to OFF then back to ACC or RUN.
• The history DTC will clear after 40 consecutive fault-free ignition cycles have occurred.

Reference Information

Schematic Reference

Passenger Seat Wiring Schematics

Connector End View Reference

Component Connector End View Index

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

1. Ignition OFF, disconnect the harness connector at the appropriate passenger seat motor listed below for which the DTC set:

• M50P Seat Front Vertical Motor - Passenger
• M55P Seat Rear Vertical Motor - Passenger
• M51P Seat Horizontal Motor - Passenger
• M56P Seat Recline Motor - Passenger

2. Ignition ON.

3. Test for greater than 10.8 V between the 12 V reference circuit listed below and ground while pressing any power seat switch.

• M50P Seat Front Vertical Motor - Driver terminal 2
• M55P Seat Rear Vertical Motor - Driver terminal 4
• M51P Seat Horizontal Motor - Driver terminal 4
• M56P Seat Recline Motor - Driver terminal 2
• If 10.8 V or less

1. Ignition OFF, disconnect the X5 harness connector at the K40P Seat Memory Control Module - Passenger.
2. Test for infinite resistance between the 12 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 12 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40P Seat Memory Control Module - Passenger.

• Go to next step: If greater than 10.8 V

4. Test for 0.2 - 2 V between the appropriate signal circuit listed below and ground.

• M50P Seat Front Vertical Motor - Driver terminal 4
• M55P Seat Rear Vertical Motor - Driver terminal 2
• M51P Seat Horizontal Motor - Driver terminal 2
• M56P Seat Recline Motor - Driver terminal 4
• If less than 0.2 V

1. Ignition OFF, disconnect the X5 harness connector at the K40P Seat Memory Control Module - Passenger.
2. Test for infinite resistance between the signal circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K40P Seat Memory Control Module - Passenger.

• If greater than 2 V

1. Ignition OFF, disconnect the X5 harness connector at the K40P Seat Memory Control Module - Passenger, ignition ON.
2. Test for less than 1 V between each signal circuit listed below and ground.
   • Front vertical sensor terminal 12
   • Seat horizontal sensor terminal 11
   • Rear vertical sensor terminal 25
   • Seat recline sensor terminal 26
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K40P Seat Memory Control Module - Passenger.

• Go to next step: If between 0.2 - 2 V

5. Test or replace the seat motor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Front Seat Tilt Adjuster Actuator Replacement
• Driver or Passenger Seat Vertical Adjuster Actuator Replacement
• Driver or Passenger Seat Recliner Actuator Replacement (Except GS) or Driver or Passenger Seat Recliner Actuator Replacement (GS)
• Control Module References for K40P Seat Memory Control Module - Passenger replacement, programming and setup

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