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Forum > Failed Smog Test > Question

Does my check engine light have to stay illuminated when I start the car to pass smog?

I have a 95 Cadillac Seville SLS Northstar with 107,000 miles. This was the first time I've failed my smog in 4 years, since I got it. I applied for CAP and got it, but the mechanic told me that it would be $7,000 to rebuild my engine & transmission to get it to pass (more than my car is worth). Another mechanic took a look (not Gold Shield) and fixed my car by giving me a tuneup & replacing my 2 oxygen sensors ($1,000). The new mechanic told me that my car won't pass the smog if the check engine light doesn't come on when I start my car, but everything on your site says it's only an issue if it stays illuminated. Who's right?
Answer:

The check engine light does have to turn "ON" when the ignition is on the "ON" position and the engine is NOT running. This indicates that the Check Engine light is functioning. Soon as the engine starts to run the Check Engine light needs to turn off automatically. If it remains ON there is an emissions related problem. posted by SmogTips Support

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