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1995 corsica

i have a 95 corsica and the car runs quiet and smooth but only when i drive at hi speed in cruise control when i tap the brake to turn off the cruise contr or even when i am not using cruise when i tap the brake to begin slowing down the engine light comes on but it never happens in town only at 55 or higher speeds anybody have any ideas i have taken it to autozone and they gave me one of those metal keys but no good can anybody help or no why the light comes on?

Metal keys??? What metal keys???

Do you have an OBDII system? Did they download fault codes?

The light could be triggered by lots of things. One is a leak in the brake booster. Have you experienced any other symptoms?

the metal key goes into the obdII system i have the 96 or newer scanner but autozone has a key for the 95 or older system dont think its the boost it only happens at hi speeds never around town i was kinda thinking it was the speed senor? what do u think

This is the OBDI engine management system. The key is inserted into the A and B terminals of the ALDL connector located below the steering column. The ignition switch is then turned to the run position. The Check Engine light will begin to flash out the DTC’s.

The most probable cause of the Check Engine light coming on under this type of driving condition is because of a lazy oxygen sensor. Here’s a site that explains how to retrieve the codes with that key, and the definitions of the codes.


Use that metal “key” and let the engine computer tell you why it’s turning on the check engine light. That’s what it’s there for.
When that “key” is used in the connector, the light will flash a trouble code…something like 4 flashes and 2 flashes. The flashes will mean to check so and so. Bring that light-flash code here and somebody will help you with it.

Thanks for the clarification guys. I always called it a “code reader”. I guess I need to get out more.