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 EnvoyFACTORY OEM SERVICE PROCEDURE
Control Units
CONTROL UNITS
| Component | Component Location |
|---|---|
| Automatic Transfer Case Control Module (ATCCM) (Pickups) | Behind center of dash, to the left of the ashtray. |
| Automatic Transfer Case Control Module (ATCCM) (Except Pickups) | Behind right front kick panel. |
| Cruise Control Module | On left side of firewall. |
| Electrohydraulic Control Unit (ECU) | On left front inner fender. |
| Electronic Brake Control Module (EBCM) | On left front inner fender, part of electrohydraulic control unit. See Figure. |
| Electronic Climate Control (ECC) Module (HVAC Controller W/ Auto A/C) | Center of dash, below radio. |
| Electronic Ignition Control Module (EICM) (2.2L VIN 4) | On right side of engine, near camshaft position sensor. Part of electronic ignition coil & assembly. See Figure. |
| Electronic Ignition Control Module (EICM) (4.3L VIN W, X) | On top right side of engine. Part of electronic ignition coil & assembly. |
| Electronic Shift Transfer Case Control Module | (ESTCCM) Behind center of dash. |
| HVAC Controller (W/ Man A/C) | Under center of dash. |
| Inflatable Restraint Sensing & Diagnostic Module (SDM) | Under console & carpet, between front seats. |
| Left Front Heated Seat Heater Module | Under left front seat. |
| Powertrain Control Module (PCM) (2.2L VIN 4) | On right front of engine compartment. |
| Remote Audio Player | Under front of floor console. |
| Remote Control Door Lock Receiver | Behind lower left side of dash. |
| Remote Function Actuator (RFA) Module | Behind left side of dash. |
| Right Front Heated Seat Heater Module | Under right front seat. |
| Sun Roof Express Module | Overhead, between front seats. |
| Truck Body Control (TBC) Module | Behind dash, mounted on heater. |
| Vehicle Control Module (VCM) (4.3L VIN W, X) | On right front of engine compartment. |
| Windshield Wiper Pulse Control Module | On center of firewall. |
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.