Here's the proper approach:
1. Identify the problem: The light is a symptom. You need to diagnose *why* the light is on. This usually requires a professional scan tool capable of reading the specific trouble codes (DTCs) stored by the vehicle's computer related to the 4WD system. Auto parts stores often offer free code reading services.
2. Possible Causes (and solutions): Some common causes for a 4WD service light on a 2001 GMC Jimmy include:
* Low transfer case fluid: Check and top off the transfer case fluid if necessary. This is a relatively simple and inexpensive fix, but unlikely to reset the light on its own if a low fluid level triggered the issue initially.
* Faulty transfer case motor: This is a more expensive repair and requires replacement of the motor or potentially the entire transfer case.
* Problems with the 4WD actuator motor: This motor engages and disengages the 4WD system. A malfunctioning motor will prevent the 4WD from engaging correctly.
* Electrical issues: Worn wires, corroded connectors, or a faulty sensor in the 4WD system can trigger the light.
* Shift motor issues: This applies if you have an electronic shift system (many do, though some are manually shifted).
3. Repair the problem: Once the problem is identified through a diagnostic scan, the necessary repairs must be made.
4. Clear the code (after repair): *After* you've fixed the underlying problem, the light will often go out automatically after a short drive. If it persists, you can use a scan tool to clear the trouble code(s) from the vehicle's computer. This is the only "reset" involved, and it's done *after* the repair, not before.
In short: Don't try to reset the light without knowing what caused it. Ignoring it could lead to more costly repairs down the road, or even dangerous driving conditions if your 4WD system is malfunctioning. Take it to a mechanic or use an OBDII scanner to properly diagnose the problem first.
