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 B1851 00: Lumbar Position Sensor FaultDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Lumbar Horizontal Position Sensor Signal | B1851 00 | B1851 00 | B1851 00 | -- |
Memory Seat/Mirror Sensor Low Reference | -- | B1851 00 | -- | -- |
Circuit/System Description
The lumbar position sensor that set this diagnostic trouble code (DTC) is directly attached to the motor it monitors. It receives a signal circuit and ground from the memory seat module (MSM). The sensor sends a voltage signal that varies with the movement of the lumbar support through the signal circuit to the MSM. Then based on this voltage signal, the MSM determines the position of the lumbar.
Conditions for Running the DTC
The MSM must be powered.
Conditions for Setting the DTC
If the MSM sees the voltage signal from this sensor as either lower than 0.25 V or higher than 4.75 V, the sensor will be considered out of range and the MSM will set this DTC.
Action Taken When the DTC Sets
All memory recall 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 0.25 V and 4.75 V 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. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Memory Seats Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool MSM Lumbar Position Sensor parameter. The reading should be between 0.25 V and 4.75 V and change while adjusting the lumbar position.
Circuit/System Testing
- Ignition OFF, disconnect the X2 harness connector at the seat lumbar motor.
- Test for less than 2 Ω between the low reference circuit terminal 2 and ground.
- Ignition ON, verify the scan tool Lumbar Position Sensor parameter is greater than 4.75 V.
- Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool Lumbar Horizontal Sensor parameter is less than 0.25 V.
- If all circuits test normal, test or replace the lumbar position sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the MSM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the MSM. |
| ⇒ | If greater than the specified range, test the signal circuit for short to voltage or an open/high resistance. If the circuit tests 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 |
