GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2008 🢒 TrailBlazer - 2WD 🢒 Driver Information and Entertainment 🢒 Cellular, Entertainment, and Navigation 🢒 DTC B1825, B1850, B1860, 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: Driver Seat Recline Position Sensor Circuit

DTC B1850: Driver Seat Lumbar Horizontal Position Sensor Circuit

DTC B2355: Driver Seat Front Vertical Position Sensor Circuit

DTC B2365: Driver Seat Rear Vertical Position Sensor Circuit

DTC B2375: Driver Seat Horizontal Position Sensor Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5-Volt Reference Terminal A3 X4

B1825, B2355, B2365, B2375

B1825, B2355, B2365, B2375

B1825, B2355, B2365, B2375

--

5-Volt Reference Terminal B3 X4

B1850, B3606, B3607

B1850, B3606, B3607

B1850, B3606, B3607

--

Recline Position Sensor Signal

B1825

B1825

B1825

--

Horizontal Position Sensor Signal

B2375

B2375

B2375

--

Rear Vertical Position Sensor Signal

B2365

B2365

B2365

--

Front Vertical Position Sensor Signal

B2355

B2355

B2355

--

Horizontal Lumbar Position Sensor Signal

B1850

B1850

B1850

--

Low Reference Terminal B11 X4

--

B1825, B2355, B2365, B2375

--

--

Low Reference Terminal B10 X4

--

B1850, B3606, B3607

--

--

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 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

Battery voltage to the seat module must be within 7-16 volts.

Conditions for Setting the DTC

The position sensor signal circuit voltage level to the MSM is not within the 0.39-4.58 volt range.

Action Taken When the DTC Sets

The memory recall functions for the seat motor with a current status DTC will be disabled.

Conditions for Clearing the DTC
    • The DTC will be stored as a history code when the fault is no longer present.
    • The history DTC will clear after 100 consecutive fault-free ignition cycles have occurred.

Diagnostic Aids
    • The scan tool may reference the Memory Seat Module as the Driver Seat Module.
    • All driver seat position sensors use common 5-volt reference and low reference circuits.
    • The driver seat lumbar position sensor and the adjustable pedal position sensors use common 5-volt reference and low reference circuits.
    • If the 5-volt reference circuit is shorted to ground or voltage multiple position sensor codes will set.
    • If the sensor low reference circuit is open multiple codes will set.

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 Verification

Ignition ON, observe the scan tool Driver Seat Module driver seat and lumbar position sensor parameters. The readings should be between 0.39 volts and 4.58 volts and change while adjusting seat and lumbar positions.

Circuit/System Testing

B1825, B2355, B2365, or B2375

  1. Ignition OFF, disconnect the harness connector at the appropriate seat position sensor.
  2. Test for less than 10 ohms between the appropriate low reference circuit listed below and ground:
    3. • Seat recline sensor terminal D
    • Front vertical sensor terminal C
    • Rear vertical sensor terminal A
    • Seat horizontal sensor terminal A
    ⇒If greater than the specified range, 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 appropriate 5-volt reference circuit listed below and ground.
    4. • Seat recline sensor terminal A
    • Front vertical sensor terminal A
    • Rear vertical sensor terminal C
    • Seat horizontal sensor terminal C
    ⇒If less than the specified range, 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 the specified range, 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 seat position parameter listed below is less than 1 volt:
    5. • Seat Horizontal Position
    • Front Vertical Position
    • Rear Vertical Position
    • Recline Position
    ⇒If greater than the specified range, test the appropriate signal circuit listed below for a short to voltage. If the circuit tests normal, replace the MSM.
    • Seat recline sensor terminal C
    • Front vertical sensor terminal B
    • Rear vertical sensor terminal B
    • Seat horizontal sensor terminal B
  5. Install a 3A fused jumper wire between the appropriate signal and 5-volt reference circuits listed below. Verify the appropriate scan tool seat position parameter is greater than 4.58 volts.
    6. • Seat recline sensor terminal C and terminal A
    • Front vertical sensor terminal B terminal A
    • Rear vertical sensor terminal B terminal C
    • Seat horizontal sensor terminal B terminal C
    ⇒If less than the specified range, 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 position sensor.

B1850

  1. Ignition OFF, disconnect the harness connector at the lumbar horizontal position sensor.
  2. Test for less than 10 ohms between the low reference circuit terminal 1 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 MSM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.
    4. ⇒If less than the specified range, 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 the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the MSM.
  4. Verify the scan tool Horizontal Lumbar Pos parameter is less than 1 volt.
    5. ⇒If greater than the specified value, 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 5-volt reference circuit terminal 3. Verify the scan tool Horizontal Lumbar Pos parameter is greater than 4.58 volts.
    6. ⇒If less than the specified range, 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 horizontal position sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Power Seat Adjuster Mechanism Replacement
    •  Front Seat Lumbar Support Replacement
    •  Control Module References for MSM replacement, programming, and setup.