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.
System Diagnostics: Mil
The Powertrain Control Module (PCM), located in engine compartment, monitors several different engine control system circuits. See PCM LOCATION table. If a malfunction occurs which affects vehicle emissions, PCM will turn on MIL the next time engine is started and the same malfunction is detected.
| Application | Location |
|---|---|
| AB & BE/BR Bodies | On Firewall, Near Wiper Motor |
| AN & DN Bodies | Right Front Fender, Near Firewall |
| TJ Body | On Firewall, Near Blower Motor |
| XJ Body | Left Front Fender, Near Radiator Support |
| ZJ Body | Right Front Fender, Near EVAP Canister |
If PCM detects a cylinder(s) misfire, lean fuel condition or a rich fuel condition, MIL is immediately turned on. On manual transmission vehicles, MIL will either flash or light continuously during an active engine misfire. On all vehicles, PCM will turn off MIL when malfunction is not detected during 3 run/stop cycles of engine of at least a 2 minute duration. MIL may be turned off by PCM, however, a DTC may remain stored depending on type of malfunction detected.
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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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