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 DIAGNOSIS (SINGLE PAGE)QUICK LOOKUPSELECTRICAL COMPONENT LOCATIONSELECTRICAL COMPONENT LOCATORCONNECTORS
1999 GMC Forward Control 5.7 R, Automatic
Electrical Component Locator: Connectors
1999 GMC Forward Control 5.7 R, AutomaticSECTION Connectors
CONNECTORS
| Component | Component Location |
|---|---|
| C100 (Black, 7 Pin) | At lower left corner of firewall. |
| C101 (Black, 38 Pin) | Above left rear of intake manifold. See Figure. |
| C102 (Black, 3 Pin) | Below generator. See Figure. |
| C103 (Black, 3 Pin) | On top of transmission. |
| C104 (Black, 2 Pin) | On engine side of firewall, near C100. |
| C105 (4.3L VIN W) (Black, 12 Pin) | Near steering gearbox. See Figure. |
| C105 (5.7L VIN R) (Black, 16 Pin) | Near steering gearbox. |
| C107 (Black, 10 Pin) | Near distributor. |
| C110 (Commercial Van) (Black, 7 Pin) | Near brake master cylinder. |
| C110 (Motor Home) (Black, 7 Pin) | Near steering gearbox. |
| C111 (Commercial Van) (Black, 3 Pin) | Near brake master cylinder. |
| C111 (Motor Home) (Black, 3 Pin) | Above steering gearbox. |
| C115 | In engine harness, 10 cm from breakout to heated oxygen sensor, bank 2, sensor 1. |
| C117 | In engine harness, 10 cm from breakout to generator. |
| C200 (Commercial Van) (Black, 36 Pin) | At left side of firewall, left of steering column. |
| C200 (Motor Home) (Gray, 36 Pin) | At left side of firewall, left of steering column. |
| C202 (Gray, 36 Pin) | At left side of firewall, left of steering column. |
| C203 (Commercial Van) (Gray, 36 Pin) | At top of steering column support. |
| C203 (Motor Home) (Gray, 36 Pin) | At left side of firewall, left of steering column. See Figure. |
| C204 | Marker lights provision for body builder. |
| C205 | Located by body builder. |
| C207 (Commercial Van) (Black, 7 Pin) | Near battery junction block. |
| C207 (Motor Home) (Gray, 7 Pin) | Near battery junction block. |
| C209 | Door ajar switch provision for body builder. |
| C210 (Commercial Van) (Brown, 2 Pin) | Dome light provision for body builder. See Figure. |
| C210 (Motor Home) (Black, 4 Pin) | On top of steering column support. |
| C211 (Commercial Van) (Black, 6 Pin) | On top of steering column support. See Figure. |
| C211 (Motor Home) (Black, 6 Pin) | On top of steering column support. |
| C212 (Commercial Van) | Park accessory provision for body builder. |
| C212 (Motor Home) | Foglight provision for body builder. |
| C213 (Commercial Van) | Foglight provision for body builder. |
| C213 (Motor Home) | Door ajar signal provision for body builder. |
| C300 (Motor Home) (Black, 15 Pin) | Near middle of chassis, at outside of left frame rail. |
| C301 (Motor Home) (Black, 3 Pin) | At left middle of transmission. |
| C303 (Black, 3 Pin) | At right frame rail, behind transmission. |
| C400 (Black, 7 Pin) | Behind fuel tank, near left frame rail. |
| C401 (Commercial Van) (Black, 7 Pin) | On left frame rail, near rear light harness. |
| C401 (Motor Home) (Black, 7 Pin) | Near left frame rail, near rear of fuel tank. |
| C402 (Commercial Van) (Black, 2 Pin) | Center high mount stop light provision for body builder. |
| C402 (Motor Home) (Gray, 4 Pin) | On right frame rail, rear of fuel tank. |
| C404 (Commercial Van) | Mid-vehicle clearance lights provision for body builder. |
| C405 | Center high mount stop light provision for body builder. |
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.