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.
2003 Chevrolet TrailBlazer 4.2 S, 4WDFACTORY OEM SERVICE PROCEDURE
Control Units
CONTROL UNITS LOCATION
| Component | Location |
|---|---|
| Auxiliary Blower Motor Processor | In rear HVAC module, behind right rear interior panel. |
| Body Control Module (BCM) | Beneath left rear seat, on rear fuse block. See Figure. |
| Driver Door Module | Below driver's door switch panel. |
| Electronic Brake Control Module | On inner left frame rail, beside transmission. |
| Front Passenger Door Module | Below front passenger door switch panel. |
| Headlamp Driver Module | On underhood fuse block. |
| Ignition Coil/Module (6) | On top of valve cover, above respective cylinder. |
| Inflatable Restraint Sensing & Diagnostic Module | Below rear of center console. |
| Inflatable Restraint Side Impact Sensing Module (Left) | In left front seat back. |
| Inflatable Restraint Side Impact Sensing Module (Right) | In right front seat back. |
| Memory Seat Module | Below left front seat. |
| Powertrain Control Module (PCM) (4.2L) | On upper left side of engine. See Figure. |
| Powertrain Control Module (PCM) (5.3L) | Near lower left front of engine. |
| Sun Roof Module | Above headliner, at rear of sun roof assembly. See Figure. |
| Transfer Case Shift Control Module | Behind lower left side of dash. See Figure. |
| Turn Signal/Hazard Flasher Module | Behind lower left side of dash. |
| Vehicle Communication Interface Module | Under right rear seat. |
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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