Reset check engine light 2004 Jeep Grand Cherokee?

You can't reliably reset a check engine light on a 2004 Jeep Grand Cherokee (or any modern vehicle) simply by disconnecting the battery or using a cheap OBDII scanner. The light comes on because the onboard diagnostic system (OBDII) has detected a problem. Resetting the light without addressing the underlying issue is pointless and potentially dangerous.

Here's the proper approach:

1. Diagnose the problem: The check engine light is a symptom, not the problem. You *must* first determine what triggered the light. This requires:

* OBDII Scanner: A decent OBDII scanner (not just a cheap code reader) is necessary. It will read the Diagnostic Trouble Codes (DTCs). These codes provide clues about the problem. Many auto parts stores will read the codes for free.

* Research: Once you have the DTCs, research them online (there are many resources available) or consult a repair manual specific to your 2004 Jeep Grand Cherokee's engine. This will help you understand the potential causes.

2. Repair the problem: Based on the DTCs and your research, fix the underlying issue. This could range from something simple (like a loose gas cap) to something more complex (requiring professional repair).

3. Clear the code (after repair): *Only* after you've fixed the problem should you attempt to clear the code. Many OBDII scanners have a "clear codes" function. Some advanced scanners even allow you to perform various tests to verify the repair.

Methods to clear the code (after repair):

* OBDII Scanner: The easiest and most reliable method. Follow the instructions for your specific scanner.

* Disconnecting the Battery (Less Reliable): Disconnecting the negative battery terminal for 15-30 minutes *might* work, but it's not guaranteed. This is a last resort and may not work for all systems or codes.

Important Considerations:

* Professional Help: If you're not comfortable diagnosing and repairing car problems yourself, take your Jeep to a qualified mechanic. Incorrect repairs can lead to further damage and safety hazards.

* State Inspections: In some areas, a check engine light may prevent your vehicle from passing inspection. Fixing the problem and clearing the code is essential for passing.

In short: Don't focus on resetting the light; focus on fixing whatever caused it in the first place. The light is a warning sign, and ignoring it could lead to more serious and costly problems down the road.