Lumbar Support Inoperative (With Memory A45)
Lumbar Support Inoperative (with Memory A45)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
A low current battery voltage is supplied at all times to the memory seat module (MSM) from the 10A MSM LOGIC fuse. This voltage is used by the MSM for logic power and to supply battery reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the MSM/LT FRT PWR SEAT 25A circuit breaker. This voltage is connected to a power rail internal to the MSM and is used to drive the power seat motors, lumbar motors, and seat heater elements on vehicles equipped with heated seats. Each seat and lumbar adjuster motor is controlled by the MSM through 2 motor control circuits. The MSM connects all motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The MSM checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat or lumbar motors.
The motor is reversible. For example, when the lumbar switch is operated to move the lumbar support forward, battery positive voltage is applied through the switch contacts and the lumbar horizontal forward switch signal circuit to the MSM. In response to this signal, the MSM applies battery voltage through the lumbar motor forward control circuit and ground through the lumbar motor rearward control circuit to the motor. The motor runs to drive the lumbar support forward toward the occupants back until the switch is released. Moving the lumbar support rearward works similarly to moving the lumbar support forward, except that battery positive voltage and ground are applied on the opposite circuits causing the motor to run in the opposite direction.
Reference Information
Schematic Reference
* Driver Seat Schematics (Driver Seat Schematics)
* Passenger Seat Schematics (Passenger Seat Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Lumbar Support Description and Operation (w/o Memory - A45) (Lumbar Support Description and Operation (w/o Memory - A45))Lumbar Support Description and Operation (with Memory - A45) (Lumbar Support Description and Operation (with Memory - A45))
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit/System Verification
1. Ignition ON, verify that none of the Memory Seat Module Lumbar Switch parameters are Active while the switch is in an inactive state.
• If either of the switch parameters is Active, refer to the Switch Circuit Test.
2. Observe the scan tool Lumbar Switch parameters while pressing the related lumbar switch. The reading should change between Inactive and Active.
• If not the specified value, refer to the Switch Circuit Test.
3. If the lumbar switch inputs to the MSM function normal, refer to the Motor Control Circuit Test.
Circuit/System Testing
Lumbar Adjuster Switch Circuit Test
1. Ignition OFF, disconnect the harness connector at the lumbar adjuster switch.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal D and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
3. Verify that the scan tool lumbar switch input parameters are Inactive.
• If not Inactive, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the memory seat module.
4. Install a 3A fused jumper wire between the B+ circuit terminal D and appropriate switch signal circuit terminal listed below. Verify the related scan tool Lumbar Switch parameter is Active.
* Lumbar forward terminal E
* Lumbar rearward terminal B
• If not Active, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the MSM.
5. If all circuits test normal, test or replace the lumbar adjuster switch.
Motor Control Circuit Test
1. Ignition OFF, disconnect the X3 harness connector at the MSM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Ignition OFF, connect the X3 harness connector at the MSM.
4. Disconnect the X1 harness connector at the seat lumbar motor.
5. Connect a test lamp between control circuit terminal A and control circuit terminal B.
6. Ignition ON, command the Lumbar Forward and Rearward with a scan tool. The test lamp should turn ON when commanding the Forward and Rearward states.
• If the test lamp remains OFF during either of the commands, test the motor control circuits for an open/high resistance. If the circuits test normal replace the MSM.
7. If all circuits test normal, test or replace the lumbar motor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Front Seat Lumbar Control Switch Replacement (Front Seat Lumbar Control Switch Replacement)
* Control Module References (Programming and Relearning)for memory seat module replacement, setup, and programming