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.
1998 GMC Forward Control 6.5 FFACTORY OEM SERVICE PROCEDURE
Electrical Component Locator: Connectors
CONNECTORS
| Component | Component Location |
|---|---|
| C100 (Black, 7 Pin) | At lower left corner of firewall. |
| C101 (Black, 7 Pin) | Above left rear of intake manifold. |
| C102 (Commercial Van) (Black, 3 Pin) | Approximately, 15 cm from ignition control module. |
| C102 (Motor Home) (Black, 3 Pin) | Below generator. |
| C103 (Black, 3 Pin) | At left lower radiator support area. |
| C104 (Black, 2 Pin) | On engine side of firewall, near C103. |
| C105 (Black, 12 Pin) | At center if intake manifold. |
| C107 (Black, 10 Pin) | Near distributor. |
| C109 (Black, 15 Pin) | Approximately, 30 cm from glow plug control breakout to engine harness. |
| C110 (Commercial Van) (Black, 7 Pin) | Near brake master cylinder. |
| C110 (Motor Home) (Black, 7 Pin) | At front of left front frame rail. |
| C111 (Commercial Van) (Black, 3 Pin) | Near brake master cylinder. |
| C111 (Motor Home) (Black, 3 Pin) | At front of left front frame rail. |
| C200 (Commercial Van) (Black, 56 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. |
| C201 (Commercial Van) (Gray, 11 Pin) | On lower steering column. |
| C201 (Motor Home) | Next to steering column. |
| C202 (Commercial Van) (Gray, 36 Pin) | At left side of firewall, left of steering column. |
| C202 (Motor Home) (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. |
| C204 | Marker lights provision for body builder. |
| C205 (Commercial Van) | Behind left side of dash. |
| C205 (Motor Home) | Located by body builder. |
| C206 (Commercial Van) | Near DRL module. |
| C206 (School Bus) | Located by body builder. |
| C207 (Commercial Van) (Black, 7 Pin) | Near battery junction block. |
| C207 (Motor Home) (Gray, 7 Pin) | Near battery junction block. |
| C208 | Approximately, 16 cm from breakout to steering column harness. |
| C209 | Door ajar switch provision for body builder. |
| C210 (Commercial Van) (Brown, 2 Pin) | Dome light provision for body builder. |
| C210 (Motor Home) (Black, 4 Pin) | On top of steering column support. |
| C211 (Black, 6 Pin) | On top of steering column support. |
| C300 (Black, 15 Pin) | Near middle of chassis, at outside of left frame rail. |
| C301 (Black, 3 Pin) | At left middle of 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 (Motor Home) (Gray, 4 Pin) | Center high mount stoplight provision for body builder. |
Factory Service Tools
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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.