Check engine light is on

Tiny
CARLLEHN
  • MEMBER
  • 1998 GMC JIMMY
  • 100,000 MILES
The rest of the Idiot Lights are not on when you first start it. They don't come on at anytime. The transmission is in high gear (not overdrive) and will not downshift. I replaced the ignition switch nothing change. These three symptoms happened at the same time.
Thursday, September 29th, 2011 AT 1:41 AM

1 Reply

Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired.

Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem. With a 1996 or newer and some 95 cars and you have an AutoZone or Advanced auto parts in your area, they will read them for free. Once you have these code numbers, we can be a lot more specific about what your problem may be.
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Thursday, September 29th, 2011 AT 2:11 AM

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