Here's the proper approach:
1. Diagnose the problem: This is the crucial first step. You need to find out *why* the CEL is on. There are several ways to do this:
* OBD-II Scanner: While the 940 isn't fully OBD-II compliant, a generic OBD-II scanner *might* provide some codes. However, a Volvo-specific scanner or software is usually necessary for a more accurate diagnosis. These scanners can read the specific Volvo diagnostic trouble codes (DTCs).
* Volvo VIDA/Dice: This is the professional-level diagnostic software used by Volvo mechanics. It's the most comprehensive way to diagnose issues. You'll need the software and an interface cable.
* Experienced Mechanic: The easiest and often most cost-effective method is to take your car to a qualified mechanic specializing in Volvos. They have the tools and expertise to diagnose and repair the issue correctly.
2. Repair the problem: Once you know the DTC(s), you can address the underlying mechanical or electrical issue. This could range from a simple sensor replacement to a more complex repair.
3. Clear the code (after repair): *Only after* successfully repairing the problem, you can clear the CEL. This is usually done through the same OBD-II scanner or Volvo VIDA/Dice software that you used for diagnosis. The process varies depending on the tool, but it usually involves selecting an option to clear codes or reset the system.
Important Considerations:
* Don't just disconnect the battery: While disconnecting the battery for a period of time might temporarily clear the CEL, it won't solve the underlying problem. The light will likely return.
* DIY risks: Working on a car's electrical system can be dangerous if you're not experienced. If you're uncomfortable diagnosing or repairing the issue yourself, it's best to leave it to a professional.
In short: Focus on fixing the problem that triggered the CEL, and the light will clear itself once the issue is resolved and the system is reset. Attempting to clear the light without addressing the root cause is ineffective and potentially harmful.
