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.
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HOMESERVICE MANUALSJEEP1991CHEROKEE 2WD L4-150 2.5L VIN P MFIREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSMALFUNCTION INDICATOR LAMPDESCRIPTION AND OPERATION
1991 Jeep Cherokee 2WD L4-150 2.5L VIN P MFI
Malfunction Indicator Lamp: Description and Operation
1991 Jeep Cherokee 2WD L4-150 2.5L VIN P MFISECTION Description and Operation
The CHECK ENGINE lamp is located in the instrument panel of the vehicle, and it is illuminated for three seconds when the ignition switch is turned ON (bulb test).
This lamp is also used as a warning lamp to indicate immediate service of the engine control system is required. This light will illuminate if an improper or missing signal, from certain sensors or emission related devices (California models only), is received by the engine controller. If this light is ON while the vehicle is driving, it is an indication that the engine control system has entered its "Limp-In Mode" to try to keep the vehicle operating until it can be serviced.
The CHECK ENGINE lamp can also be used to display fault codes that have been stored in the engine controller's memory due to a system failure. To display codes with the CHECK ENGINE lamp, cycle the ignition switch ON, OFF, ON, OFF, ON within five seconds and all of the fault codes stored will be displayed in a series of flashes representing digits. Fault codes can also be extracted using the DRB II or an equivalent scan tool.
This lamp is also used as a warning lamp to indicate immediate service of the engine control system is required. This light will illuminate if an improper or missing signal, from certain sensors or emission related devices (California models only), is received by the engine controller. If this light is ON while the vehicle is driving, it is an indication that the engine control system has entered its "Limp-In Mode" to try to keep the vehicle operating until it can be serviced.
The CHECK ENGINE lamp can also be used to display fault codes that have been stored in the engine controller's memory due to a system failure. To display codes with the CHECK ENGINE lamp, cycle the ignition switch ON, OFF, ON, OFF, ON within five seconds and all of the fault codes stored will be displayed in a series of flashes representing digits. Fault codes can also be extracted using the DRB II or an equivalent scan tool.
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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.