Check Engine Light is On: 1990 GMC C3500 Sierra 7.4L V8 Extended Cab Pickup

A check engine light can indicate a broad spectrum of problems with your 1990 GMC C3500. If you have a flashing check engine light, turn off the engine immediately to prevent potential motor damage. Whereas a steady check engine light may mean you merely need to tighten you gas cap next time you stop in order to reset the service engine soon light. The video above shows how to locate the on board diagnostics OBD plug location on your 1990 C3500, how to read the trouble codes and how to reset or clear the check engine light using a scanner on your C3500.

Is it OK to drive with a check engine light on? Intermittent Check Engine Light: If the check engine light on your 1990 C3500 is not steady, try to take note of the conditions when this happens. For example, does it happen when you accelerating, driving on the highway or does it appear at low speeds? This will help your mechanic evaluate the issue. Steady Check Engine Light: If your check engine light is on every time you operate your C3500, you need to have it checked as soon as possible, especially if you notice performance problems or unusual noises. Flashing Check Engine Light: If your check engine light is flashing, stop driving your C3500 and have it towed to your nearest mechanic – a blinking check engine light means you probably have a very serious problem with your car and you risk ruining your engine by driving it. If you are unsure about what your diagnostic trouble codes mean after finding the C3500 OBD port location and scanning the codes; have your C3500 diagnosed by a professional automotive technician.