GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2007 🢒 Lucerne 🢒 DTC 🢒 DTC B1825, B1850, B1860, B2105, B2355, B2365, or B2375

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 B1825 01: Seat Recline Position Sensor Circuit Short to Battery

DTC B1825 06: Seat Recline Position Sensor Circuit Short to Ground or Open

DTC B1825 5A: Seat Recline Position Sensor Direction of Motion Reversed

DTC B1850 01: Seat Lumbar Horizontal Position Sensor Circuit Short to Battery

DTC B1850 06: Seat Lumbar Horizontal Position Sensor Circuit Short to Ground or Open

DTC B1850 5A: Seat Lumbar Horizontal Position Sensor Direction of Motion Reversed

DTC B1860 01: Seat Lumbar Vertical Position Sensor Circuit Short to Battery

DTC B1860 06: Seat Lumbar Vertical Position Sensor Circuit Short to Ground or Open

DTC B1860 5A: Seat Lumbar Vertical Position Sensor Direction of Motion Reversed

DTC B2355 01: Left Front Seat Front Vertical Position Sensor Circuit Short to Battery

DTC B2355 06: Left Front Seat Front Vertical Position Sensor Circuit Short to Ground or Open

DTC B2355 5A: Left Front Seat Front Vertical Position Sensor Direction of Motion Reversed

DTC B2365 01: Left Front Seat Rear Vertical Position Sensor Circuit Short to Battery

DTC B2365 06: Left Front Seat Rear Vertical Position Sensor Circuit Short to Ground or Open

DTC B2365 5A: Left Front Seat Rear Vertical Position Sensor Direction of Motion Reversed

DTC B2375 01: Left Front Seat Assembly Horizontal Position Sensor Circuit Short to Battery

DTC B2375 06: Left Front Seat Assembly Horizontal Position Sensor Circuit Short to Ground or Open

DTC B2375 5A: Left Front Seat Assembly Horizontal Position Sensor Direction of Motion Reversed

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Memory Seat/Mirror Sensor Low Reference

--

B1825 01, B1850 01, B1860 01, B2355 01, B2365 01, B2375 01

--

B1825 5A, B1850 5A, B1860 5A, B2355 5A, B2365 5A, B2375 5A

5-Volt Reference

B1395 02, B1825 06, B1850 06, B1860 06, B2355 06, B2365 06, B2375 06

B1825 06, B1850 06, B1860 06, B2355 06, B2365 06, B2375 06

B1395 05, B1825 01, B1850 01, B1860 01, B2355 01, B2365 01, B2375 01

B1825 5A, B1850 5A, B1860 5A, B2355 5A, B2365 5A, B2375 5A

Driver Seat Front Vertical Position Sensor Signal

B2355 06

B2355 06

B2355 01

--

Driver Seat Rear Vertical Position Sensor Signal

B2365 06

B2365 06

B2365 01

--

Driver Seat Horizontal Position Sensor Signal

B2375 06

B2375 06

B2375 01

--

Driver Seat Lumbar Vertical Position Sensor Signal

B1860 06

B1860 06

B1860 01

--

Driver Seat Lumbar Horizontal Position Sensor Signal

B1850 06

B1850 06

B1850 01

--

Driver Seat Recline Position Sensor Signal

B1825 06

B1825 06

B1825 01

--

Driver Seat Front Vertical Motor Down Control

B3920 02

1

B3920 01

B2355 5A

Driver Seat Front Vertical Motor Up Control

B3920 02

1

B3920 01

B2355 5A

Driver Seat Rear Vertical Motor Down Control

B3920 02

1

B3920 01

B2365 5A

Driver Seat Rear Vertical Motor Up Control

B3920 02

1

B3920 01

B2365 5A

Driver Seat Horizontal Motor Forward Control

B3920 02

1

B3920 01

B2375 5A

Driver Seat Horizontal Motor Rearward Control

B3920 02

1

B3920 01

B2375 5A

Driver Seat Recline Motor Forward Control

B3920 02

1

B3920 01

B1825 5A

Driver Seat Recline Motor Rearward Control

B3920 02

1

B3920 01

B1825 5A

Driver Seat Lumbar Motor Down Control

B3920 02

2

B3920 01

B1860 5A

Driver Seat Lumbar Motor Up Control

B3920 02

2

B3920 01

B1860 5A

Driver Seat Lumbar Motor Forward Control

B3920 02

2

B3920 01

B1850 5A

Driver Seat Lumbar Motor Rearward Control

B3920 02

2

B3920 01

B1850 5A

1. Power seat inoperative

2. Lumbar inoperative

Circuit/System Description

The position sensor that set 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 ground 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

The MSM must be powered.

Conditions for Setting the DTC

B1825, B1850, B1860, B2355, B2365, B2375 01

If the MSM sees the analog input from this sensor is greater than 4.75 volts, the sensor will be considered out of range and the MSM will set this DTC.

B1825, B1850, B1860, B2355, B2365, B2375 06

If the MSM sees the analog input from this sensor is less than 0.22 volt , the sensor will be considered out of range and the MSM will set this DTC.

B1825, B1850, B1860, B2355, B2365, B2375 5A

This DTC will set, if the MSM is controlling a motor in one direction and its 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.

Action Taken When the DTC Sets

All memory recall and seat massage functions will be disabled.

Conditions for Clearing the DTC
    • The current DTC will clear and set to history, when the MSM sees the analog input from the sensor as between 0.22 volt and 4.75 volts and the ignition is cycled OFF then back to ACC or RUN.
    • The history DTC will clear after 50 consecutive fault-free ignition cycles have occurred.

Diagnostic Aids
    • All position sensors use common ground and 5-volt reference circuits.
    • If the 5-volt reference circuit is shorted to voltage multiple position sensor codes will set.
    • If the 5-volt reference circuit is shorted to ground multiple position sensor codes will set.
    • If the sensor ground circuit is open multiple codes will set.
    • DTC failure type 5A will set if the sensor setting this DTC is either mounted or wired incorrectly, or the polarity of the motor control circuits are reversed.

Reference Information

Schematic Reference

Driver Seat Schematics

Connector End View Reference

Power Seat Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Output Controls
    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Ignition ON, observe the scan tool Driver Seat and Lumbar Position Sensor parameters. The readings should be between 0.22 volt and 4.75 volts and change while adjusting seat and lumbar positions.

Circuit/System Testing

B1825

  1. Ignition OFF, disconnect the (C2) harness connector at the seat recline motor.
  2. Ignition OFF, test for less than 2 ohms of resistance between the low reference circuit terminal 3 and ground.
    3. ⇒If greater than 2 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.
    4. ⇒If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
    ⇒ If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the MSM.
  4. Verify the scan tool Driver Seat Recline Sensor parameter is less than 2 volts.
    5. ⇒If greater than 2 volts, test the signal circuit terminal 2 for a short to voltage. If the circuit tests normal, replace the MSM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 2 and the 5-volt reference circuit terminal 1. Verify the scan tool Driver Seat Recline Sensor parameter is greater than 4.75 volts.
    6. ⇒If less than 4.75 volts, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
  6. If all circuits test normal, test or replace the seat recline position sensor.

B2355, B2365, B2375

  1. Ignition OFF, disconnect the (C2) harness connector at the seat adjuster motor assembly.
  2. Ignition OFF, test for less than 2 ohms of resistance between the low reference circuit terminal 2 and ground.
    3. ⇒If greater than 2 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 6 and ground.
    4. ⇒If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
    ⇒ If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the MSM.
  4. Verify the appropriate scan tool Driver Seat Sensor parameter is less than 2 volts.
    5. ⇒If greater than 2 volts, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.
    • Seat front vertical position sensor terminal 1
    • Seat rear vertical position sensor terminal 5
    • Seat horizontal position sensor terminal 3
  5. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit terminal 6. Verify the appropriate scan tool Driver Seat position sensor parameter is greater than 4.75 volts.
    6. • Seat front vertical position sensor terminal 1
    • Seat rear vertical position sensor terminal 5
    • Seat horizontal position sensor terminal 3
    ⇒If less than 4.75 volts, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
  6. If all circuits test normal, test or replace the seat adjuster motor assembly.

B1850, B1860

  1. Ignition OFF, disconnect the (C2) harness connector at the seat lumbar motor assembly.
  2. Ignition OFF, test for less than 2 ohms of resistance between the low reference circuit terminal A and ground.
    3. ⇒If greater than 2 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C and ground.
    4. ⇒If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
    ⇒ If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the MSM.
  4. Verify the appropriate scan tool Lumbar Sensor parameter is less than 2 volts.
    5. ⇒If greater than 2 volts, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.
    • Lumbar vertical position sensor terminal B
    • Lumbar horizontal position sensor terminal D
  5. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit terminal C. Verify the appropriate scan tool Lumbar Sensor parameter is greater than 4.75 volts.
    6. • Lumbar vertical position sensor terminal B
    • Lumbar horizontal position sensor terminal D
    ⇒If less than 4.75 volts, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
  6. If all circuits test normal, test or replace the lumbar motor assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Seat Adjuster Replacement
    •  Front Seat Recliner Position Sensor Replacement
    •  Front Seat Lumbar Support Replacement
    •  Control Module References for memory seat module replacement, setup, and programming