GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Jimmy - 4WD 🢒 DTC 🢒 DTC B1785 LF Seat Motor #5 Recline Circuit Malfunction

For wiring diagrams, refer to

Seat Adjuster Memory Module, Transducers and Motors


Object Number: 548917 Size: FS
Power Seat Systems Components
Memory Seat Circuit Description
Power, Ground, Data Link Connector (DLC) and Power Seat Adjuster Switch
Handling ESD Sensitive Parts Notice
Power Seat Connector End Views
Handling ESD Sensitive Parts Notice
 .

Circuit Description

The seat adjuster memory module controls the seat recliner motor power and ground through CKT 276 (LT GRN) and CKT 277 (LT BLU). The seat adjuster memory module also senses the seat recliner motor position through a hall sensor within the motor through CKT 570 (WHT/BLK) while utilizing CKT 570A (BLK) as a sensor ground.

Conditions for Setting the DTC

The DTC will set if the seat adjuster memory module detects through the hall sensor that the recliner motor is not responding to the seat adjuster memory module commands due to the following conditions:

    • An open circuit
    • A short to ground
    • A short to power
    • An inoperative motor

Conditions for Clearing the DTC
    • A history DTC will clear after 100 consecutive fault free ignition cycles.
    • Use a scan tool in order to clear history and current DTCs.

Diagnostic Aids

One or more of the following conditions may be the cause of an intermittent failure:

    • A poor connection
    • A break in the wire insulation that exposes the internal wire
    • A wire broken inside the insulation

Test Description

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

  1. This step inspects for current DTCs.

    2.

  2. This step locates and repairs the open(s) in the wiring between the seat recliner motor and the seat adjuster memory module.

    3.

  3. This step locates and repairs the short(s) to ground in the wiring between the seat recliner motor and the seat adjuster memory module.

    4.

  4. This step verifies that the seat adjuster memory module is supplying voltage to the seat recliner motor.

    5.

  5. This step replaces a defective seat recliner motor.

    6.

  6. This step replaces a defective seat adjuster memory module.

Step

Action

Value(s)

Yes

No

1

Did you perform the Power Seat Systems Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Power Seat Systems

2

  1. Turn the ignition and start switch to the OFF position.
  2. Install the scan tool.
  3. Turn the ignition and start switch to the RUN position.
  4. Using the scan tool, clear the DTCs. Refer to Diagnostic Trouble Code (DTC) Clearing .
  5. Operate the seat adjuster memory module controls.

Does DTC B1785 reset?

--

Go to Step 3

Go to Diagnostic System Check - Power Seat Systems

3

  1. Disconnect the seat adjuster memory module and the motor.
  2. Test each of the following power recliner motor circuits for an open:
    3. • CKT 276 (LT GRN)
    • CKT 277 (LT BLU)

Refer to Circuit Testing and Wiring Repairs in wiring systems.

Did you find and correct the condition?

--

Go to Diagnostic System Check - Power Seat Systems

Go to Step 4

4

  1. Disconnect the seat adjuster memory module.
  2. Test each of the following power recliner motor circuits for a short to ground:
    3. • CKT 276 (LT GRN)
    • CKT 277 (LT BLU)

Refer to Circuit Testing and Wiring Repairs in wiring systems.

Did you find and correct the condition?

--

Go to Diagnostic System Check - Power Seat Systems

Go to Step 5

5

  1. Reconnect the seat adjuster memory module connector.
  2. Disconnect the power recliner motor.
  3. Test the following power recliner motor circuits for voltage:
    4. • CKT 276 (LT GRN)
    • CKT 277 (LT BLU)

Refer to Circuit Testing in wiring systems.

Is voltage present when the seat recliner switch is in the FORWARD or BACK positions?

--

Go to Step 6

Go to Step 7

6

Replace the power recliner motor. Refer to Front Seat Back Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - Power Seat Systems

--

7

Replace the seat adjuster memory module. Refer to Memory Seat Control Module Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - Power Seat Systems

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