GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 DTC 🢒 DTC B1735, B1740, B1745, B1750, B1755, B1760, B1815, B1820, B1830, B1835, B1840, B1845, B1940, or B1945

Circuit Description

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:

    • DTC B1735 LF Seat Front Up Switch Circuit
    • DTC B1740 LF Seat Front Down Switch Circuit
    • DTC B1745 LF Seat Rear Up Switch Circuit
    • DTC B1750 LF Seat Rear Down Switch Circuit
    • DTC B1755 LF Seat Assembly Forward Switch Circuit
    • DTC B1760 LF Seat Assembly Rearward Switch Circuit
    • DTC B1815 LF Seat Recline Forward Switch Circuit
    • DTC B1820 LF Seat Recline Rearward Switch Circuit
    • DTC B1830 LF Seat Lumbar Forward Switch Circuit
    • DTC B1835 LF Seat Lumbar Rearward Switch Circuit
    • DTC B1840 LF Seat Lumbar Up Switch Circuit
    • DTC B1845 LF Seat Lumbar Down Switch Circuit

Conditions for Running the DTC

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

Conditions for Setting the DTC
    • 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.
    • 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.
    • A switch DTC will not set if DTC B1327 current.

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

Conditions for Clearing the DTC

The DTC automatically clears when the switch circuit setting the DTC is no longer active.

Diagnostic Aids

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

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step checks the existing state of the driver's seat switch by using the current state of the signal parameter. If all of the seat switch parameters display active, possibly one of the seat switch signal circuits is shorted to voltage.

    2.

  2. When the seat adjuster switch is disconnected, this step determines if the seat switch contacts are stuck closed, or if one of the switch signal circuits is possibly shorted to battery positive voltage.

Step

Action

Yes

No

Schematic Reference: Driver Seat Schematics

Connector End View Reference: Power Seat Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the appropriate seat or lumbar switch parameter in the Driver position Module data list.

Does the scan tool display Inactive?

Go to Step 3

Go to Step 4

3
  1. With a scan tool, observe the appropriate seat or lumbar switch parameter.
  2. Activate the appropriate seat or lumbar switch.

Does the switch parameter change state?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the appropriate seat or lumbar switch harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe all of the switch parameters in the Driver Position Module data list.

Does the scan tool display Inactive for all of the parameters?

Go to Step 7

Go to Step 5

5

Test the switch signal circuit that displays active for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 6

6

Inspect for poor connections at the harness connector of the memory seat module (MSM)/driver position module (DPM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 8

7

Inspect for poor connections at the harness connector of the seat adjuster switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

Replace the MSM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 10

--

9

Replace the seat adjuster switch. Refer to Power Seat Switch Replacement .

Did you complete the replacement?

Go to Step 10

--

10
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK