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.
Engine Control Module: Service and Repair
1991 Cadillac Seville V8-300 4.9LSECTION Service and Repair
Powertrain Control Module (PCM):
Service of the PCM should normally consist of either replacement of the PCM or a MEM-CAL change. If the diagnostic procedures call for the PCM to be replaced, the Memory-Calibration unit (MEM-CAL) and PCM should be checked first to see if they are the correct parts. Also, perform the PCM Replacement Check, CHART C-1, before replacing the PCM to assure that the replacement PCM will not be damaged.
When replacing a production PCM with a service PCM, transfer the broadcast code and production number from the production unit to the service unit. Also, during replacement, the PROM, and the MEM-CAL must be removed from the PCM being replaced and transferred to the new unit.
1. Disconnect battery ground cable.
2. Then disconnect two computer electrical connectors.
3. Remove computer mounting hardware.
4. Remove computer from passenger compartment.
5. Reverse procedure to install.
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.