The on-board computer in your Jeep monitors various systems and uses the data to adjust ignition timing, fuel injection and transmission shifting to provide the best compromise between performance and efficiency. When a system or component fails, the computer will store a diagnostic code and turn on the "Check Engine" light located on the dash. Clearing the diagnostic codes from the on-board computer memory in your Jeep Cherokee Laredo will reset the "Check Engine" warning light on the dash and remove the code from the memory.
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Things you need
- Wrench set
- Code reader
Read and record the diagnostic codes stored in the Jeep on-board computer for future use. To enter self diagnostics and read the codes, cycle the ignition key off and on three times within five seconds and count the flashes of the "Check Engine" light. Turn the ignition key to the "off" position.
Disconnect the negative battery cable from the battery using a 1/2 inch wrench to loosen the cable end bolt. Twist and pull upward on the cable end until it slides off the terminal.
Wait 10 minutes for the power in the computer to dissipate and reset the memory in the on-board computer. Reinstall the negative battery cable and tighten the cable end bolt securely.
Turn the ignition key to the "off" position. Attach the code reader to the vehicle's diagnostic connector located under the driver-side dash to the left of the steering column. Turn the ignition key to the "on" position.
Push the "Read Codes" button on the code reader. Wait for a few seconds and the stored codes will be displayed on the reader's screen. Record the codes for use later if needed.
Press the "Erase Codes" button on the reader and wait for the "Codes Erased" message to appear on the reader's screen. Turn the ignition key to the "off" position and disconnect the reader from the vehicle.
Tips and warnings
- If the problem that triggered the warning light has not been addressed, the light is likely to switch on again soon.