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.
1990 Chevrolet Forward Control 7.4 N, StandardFACTORY OEM SERVICE PROCEDURE
Control Units
CONTROL UNITS LOCATION
| Component | Location | |
|---|---|---|
| Audio Alarm Module | On bracket, to left of steering column. | |
| Cruise Control Module | On brake pedal bracket. | |
| Electronic Control Module (ECM) | ||
| 4.3L | Under driver's seat. See Figure. | |
| 5.0L & 5.7L - 1989 | Under driver's seat. See Figure. | |
| 5.0L & 5.7L - 1990 | Under driver's seat. See Figure. | |
| 7.4L - 1989 | Under driver's seat. See Figure. | |
| 7.4L - 1990 | Under driver's seat. See Figure. | |
| Elect. Spark Control (ESC) Module | ||
| 4.3L | Under driver's seat. See Figure. | |
| 5.0L & 5.7L - 1989 | Under driver's seat. See Figure. | |
| 5.0L & 5.7L - 1990 | Under driver's seat. See Figure. | |
| Glow Plug Controller (Diesel) | ||
| Diesel Component View | On left rear of intake manifold. See Figure. | |
| Diesel Engine Component View | On left rear of intake manifold. See Figure. | |
| Hot Fuel Handling Module | ||
| 5.0L & 5.7L - 1989 | Under driver's seat. See Figure. | |
| 5.0L & 5.7L - 1990 | Under driver's seat. See Figure. | |
| 7.4L - 1989 | Under driver's seat. See Figure. | |
| 7.4L - 1990 | Under driver's seat. See Figure. | |
| Hydro-Boost Elect. Delay Module | Behind left side of instrument panel. | |
| Light Driver Module (Diesel) | Under right side of dash. | |
| Power Door Lock Delay Module | Above left kick panel. | |
| Pulse Wiper Control Module | Taped to harness, at right side of steering column. | |
| RWAL Elect. Control Unit | In engine compartment on bracket attached to master cylinder. | |
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.