Seat System: Diagnosis Cadillac STS I

Diagnostic Starting Point - Seats

Before you begin any diagnostic procedure, always review the system Description and Operation. Reviewing the Description and Operation will help you determine the correct diagnostic procedure when a malfunction exists. Reviewing the Description and Operation will also help you determine if the condition described by the customer is normal operation.

After reviewing the system description and operation, always begin the system diagnosis with the Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system.
2. The ability of the control modules to communicate through the serial data circuit.
3. The identification of any stored diagnostic trouble codes and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Output Controls

Driver Position Module (DPM) Output Controls

Scan Tool Data List

Driver Position Module (DPM) Data List

Climate Control Panel (CCP) Data List

Circuit Description

Battery positive voltage is supplied to the memory seat module (MSM)/driver position module (DPM) from the seats circuit breaker located in the left rear fuse block. When commanded, this voltage is used by the MSM/DPM to power the seat motors through the motor control circuits. During memory recall functions and manual seat functions, the driven motor current is monitored through the motor control circuits by the MSM/DPM. When an overcurrent condition is detected, the MSM/DPM disables the seat motors in order to protect the internal MSM/DPM circuitry.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1335 Device Power 3 Circuit Range/Performance

Conditions for Running the DTC

The MSM/DPM monitors for overcurrent only when the seat motors are active.

Conditions for Setting the DTC

The MSM/DPM will set DTC B1335 when the measured current exceeds 81 amps for 100 milliseconds.

Action Taken When the DTC Sets

1. All memory recalls in progress are aborted.
2. The MSM/DPM will not respond to manual movements of the affected motor.

Conditions for Clearing the DTC

The MSM/DPM does not detect an overcurrent condition during seat movement.

Diagnostic Aids

The MSM is also known as the DPM for this vehicle.

When the power seat switches are pressed they send a 12-volt signal to the memory seat module (MSM). The MSM then commands the driver seat to move in response to the switch signals.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC B1735 LF Seat Front Up Switch Circuit
2. DTC B1740 LF Seat Front Down Switch Circuit
3. DTC B1745 LF Seat Rear Up Switch Circuit
4. DTC B1750 LF Seat Rear Down Switch Circuit
5. DTC B1755 LF Seat Assembly Forward Switch Circuit
6. DTC B1760 LF Seat Assembly Rearward Switch Circuit
7. DTC B1815 LF Seat Recline Forward Switch Circuit
8. DTC B1820 LF Seat Recline Rearward Switch Circuit
9. DTC B1830 LF Seat Lumbar Forward Switch Circuit
10. DTC B1835 LF Seat Lumbar Rearward Switch Circuit
11. DTC B1840 LF Seat Lumbar Up Switch Circuit
12. DTC B1845 LF Seat Lumbar Down Switch Circuit

The MSM must be powered and cannot have DTC B1327 - Battery Voltage Low as an active DTC for this DTC to set.

1. If a seat switch continues to be active for 30 seconds after a motor controlled by that switch reaches the end of its travel, the switch will be considered shorted and the MSM will set the DTC.
2. If a position sensor DTC is current and the associated switch is active for 30 continuous seconds, the switch will be considered shorted and the MSM will set a switch DTC.
3. A switch DTC will not set if DTC B1327 current.

1. A motor output driven in response to a switch considered failed, is deactivated for both directions.
2. All memory recall commands are ignored.
3. The MSM will respond to any other switch signal that has not set a DTC.

The DTC automatically clears when the switch circuit setting the DTC is no longer active.

The MSM is also known as the driver position module (DPM) for this vehicle.

The potentiometer type position sensor that sets this DTC is an internal part of the seat directional motor. It receives a 5-volt reference and low reference from the memory seat module (MSM). The sensor sends a voltage signal that is pulled up to voltage by the MSM. This voltage signal varies with the movement of the seat. Then based on this voltage signal, the MSM determines the position of the seat.

This diagnostic procedure supports the following DTCs

1. DTC B1825 Seat Recline Position Sensor Circuit
2. DTC B1850 Seat Lumbar Horizontal Position Sensor Circuit
3. DTC B1860 Seat Lumbar Vertical Position Sensor Circuit
4. DTC B2355 Seat Front Vertical Position Sensor Circuit
5. DTC B2365 Seat Rear Vertical Position Sensor Circuit
6. DTC B2375 Seat Assembly Horizontal Position Sensor Circuit

This Vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC B1825, B1850, B1860, B2355, B2365, or B2375

The MSM must be powered and cannot have B1325 Battery Voltage Low as an active DTC for this DTC to set.

If the MSM sees the voltage signal from this sensor as either lower than 0.25 volts or higher than 4.75 volts, the sensor will be considered out of range and the MSM will set this DTC.

The MSM disables all memory recall commands of the motor monitored by the sensor. The motor will respond to manual positioning commands.

The MSM will clear the DTC when it detects that the voltage from the sensor signal circuit is between 0.25 volts and 4.75 volts.

1. The MSM is referenced in the Tech 2 as the driver position module (DPM) for this vehicle.
2. All position sensors use common low reference and 5-volt reference circuits.
3. If the 5-volt reference circuit is shorted to voltage multiple codes will set.
4. If the 5-volt reference circuit is shorted to ground multiple codes will set.
5. If the sensor low reference circuit is open multiple codes will set.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the power seats. Refer to «Checking Aftermarket Accessories»(ref-197533-S03944243902005101200000) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect the seat adjuster track for conditions which may cause binding or objects within the seat adjustment range which obstruct movement or interfere with wiring.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Power Seat Inoperative (w/o A45)»(ref-197561-S04281260762005101200000) or «Power Seat Inoperative (with A45)»(ref-197561-S40178232772005101200000)
2. «Lumbar Support Inoperative (w/o A45)»(ref-197561-S28955693082005101200000) or «Lumbar Support Inoperative (with A45)»(ref-197561-S39157976702005101200000)
3. «Vented Seat Inoperative»(ref-197561-S12053643452005101200000)
4. «Vented Seat Always On»(ref-197561-S16286944092005101200000)
5. «Heated Seat Always On»(ref-197561-S15378880702005101200000)
6. «Heated Seat Inoperative»(ref-197561-S42112790052005101200000)
7. «Heated Seat Always On - Rear»(ref-197561-S11244194762005101200000)
8. «Heated Seat Inoperative - Rear»(ref-197561-S01344799262005101200000)
9. «Heated Seat Switch Indicator Malfunction - Rear»(ref-197561-S09156392082005101200000)

The memory seat module (MSM) is also referenced as the driver position module (DPM) for this vehicle.

The memory seat module (MSM) is also referenced as the driver position module (DPM) for this vehicle.

Lumbar Support Inoperative (with A45)