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.
1991 Mercury Cougar LS, 3.8 4FACTORY OEM SERVICE PROCEDURE
Circuit Test Aa - Electronic Control Module (ECM) Diagnosis
- Code 11 And/Or 88 Or 89: Electrical Disturbance Check Record all trouble codes. Drive vehicle above 25 MPH to clear memory. Recheck for trouble codes. If Codes 11 and/or 88 or 89 set again, replace ECM. If no trouble codes are indicated or any other code appears, service appropriate code.
- Code 12: ECM Failure If trouble Code 12 appears, replace ECM.
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.
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