GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Envoy - 4WD 🢒 DTC 🢒 DTC B1780 LF Seat Motor #4 Rear Vertical 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 rear height motor power and ground through CKT 282 (YEL) and CKT 283 (LT BLU). The seat adjuster memory module also senses the seat rear height motor position through the seat rear height transducer, utilizing CKT 568B (RED) for reference voltage and utilizing CKT 568A (BLK) as a sensor ground.

Conditions for Setting the DTC

The DTC will set if the seat adjuster memory module detects that the rear height 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 open(s) in the wiring between the seat rear height motor and the seat adjuster memory module.

    3.

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

    4.

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

    5.

  5. This step replaces a defective seat rear height 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?

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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 B1780 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 seat rear height motor circuits for an open:
    3. • CKT 282 (YEL)
    • CKT 283 (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 seat rear height motor circuits for a short to ground:
    3. • CKT 282 (YEL)
    • CKT 283 (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 seat rear height motor.
  3. Test the following seat rear height motor circuits for voltage:
    4. • CKT 282 (YEL)
    • CKT 283 (LT BLU)

Refer to Circuit Testing in wiring systems.

Is voltage present when the seat rear height switch is in the UP or DOWN positions?

--

Go to Step 6

Go to Step 7

6

Replace the seat rear height motor. Refer to Front Seat Adjuster 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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