Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 743 (SEAT SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESPOWER SEAT INOPERATIVE (WITHOUT MEMORY)
1999 GMC Forward Control 5.7 R, Automatic
Power Seat Inoperative (Without Memory)
1999 GMC Forward Control 5.7 R, AutomaticSECTION Power Seat Inoperative (Without Memory)
WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
Power Seat Inoperative (Without Memory)
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Power Seats Schematics DEFINITION: One or more of the driver or passenger power seat functions are inoperative. |
|||
| 1 | Did you review the Power Seat System Description and Operation and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Seats |
| 2 | Attempt to operate all of the power seat adjustments through their full range. Do all of the power seat functions operate properly? |
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Are all the power seat inoperative in all direction? | Go to Step 4 | Go to Step 10 |
| 4 |
|
Go to Step 5 | Go to Step 19 |
| 5 | Connect a test lamp between the battery positive voltage supply circuit at the harness connector pin C3-A and a good ground. Does the test lamp illuminate when the battery positive supply circuit contacted to a good ground? |
Go to Step 6 | Go to Step 20 |
| 6 | Connect the test lamp between the battery positive voltage and the ground circuit of the seat relay center. Does the test lamp illuminate? |
Go to Step 7 | Go to Step 21 |
| 7 |
|
Go to Step 8 | Go to Step 12 |
| 8 |
|
Go to Step 17 | Go to Step 16 |
| 9 |
|
Go to Step 10 | Go to Step 13 |
| 10 | Connect a fused jumper wire from the inoperative power seat switch signal circuit to a good ground. Does the seat adjuster motor operate when the switch signal circuit contacted to a good ground? |
Go to Step 14 | Go to Step 11 |
| 11 |
|
Go to Step 18 | Go to Step 15 |
| 12 | Test the ground circuit of the seat adjuster switch for an open or high resistance. Refer to Circuit Testing
and Wiring Repairs
or Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 16 |
| 13 | Test the inoperative power seat switch signal circuit between the seat relay center harness connector and the seat relay center for open or high resistance, or short to ground. Refer to Circuit Testing
and Wiring Repairs
or Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 16 |
| 14 | Test the inoperative power seat adjuster switch signal circuit for an open or high resistance or short to ground. Refer to Circuit Testing
and Wiring Repairs
or Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 17 |
| 15 | Test the seat motor control circuit for open or high resistance. Refer to Circuit Testing
and Wiring Repairs
or Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 16 |
| 16 | Inspect for poor connection at the harness connector of the seat relay center. Refer to Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 24 |
| 17 | Inspect for poor connection at the harness connector of the seat adjuster switch. Refer to Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 22 |
| 18 | Inspect for poor connection at the harness connector of the seat adjuster motor. Refer to Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | Go to Step 23 |
| 19 | Repair the battery positive voltage supply circuit at the harness connector pin C1-3 for open or high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs or Connector Repairs in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | - |
| 20 | Repair the battery positive voltage supply circuit at the harness connector pin C3-A for open or high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs or Connector Repairs in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | - |
| 21 | Repair the ground circuit of the seat relay center for open or high resistance. Refer to Circuit Testing and Wiring Repairs or Connector Repairs in Wiring Systems. Did you find and correct the condition? |
Go to Step 25 | - |
| 22 | Replace the seat adjuster switch. Refer to Seat Switch Replacement - Power . Is the repair complete? |
Go to Step 25 | - |
| 23 | Replace the inoperative seat adjuster motor. Refer to Seat Adjuster Motor Replacement - Front . Is the repair complete? |
Go to Step 25 | - |
| 24 | Replace the seat relay center. Is the repair complete? |
Go to Step 25 | - |
| 25 | Operate the system in order to verify the repair. Did you correct the condition? |
System OK | Go to Step 3 |
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.