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Ron Z.
Ron Z., - Chevy Tech -
Category: Chevy
Satisfied Customers: 18961
Experience:  18+yrs experience. State Inspector and Chevy Diagnostics
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Chevy trailblazer: Service Engine Soon..50,000 miles..suv runs great.

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Service Engine Soon dashboard light on my Chevy Trailblazer 4.2L, comes on and goes off after a day or two, then comes on again after another day. This has been happening for 50,000 miles. The suv runs great. Once before I took it in to check on this problem, they changed a fuel injector. Another time I took it in for the recurring problem, they said it was the gas cap. I replaced the gas cap, and it still happens. It feels like it is just suggesting to take it in for service so you can give some money to fix something that doesn't need fixing. I don't trust the light, because the suv has been running good for a long time. Any suggestions?


When the Service Engine Soon light comes on, but you experience no drivability issues (stalling, skipping, surging, etc) than most likely the fault is in the EVAP (emissions) system. Unfortunately, there are literally dozens of parts/sensors in this system. The fuel cap is just one of many that is monitored. You best, XXXXX XXXXX at this point is to have the current codes read from the computer. To avoid the cost of diagnostic fees, you can go to any local AutoZone location, and they'll do it for Free. Once you have these "p-codes" you can more efficiently diagnose the problem.


Edited by DriveFast1971 on 6/9/2010 at 6:36 PM EST
Customer: replied 7 years ago.
The suv runs smooth and no stalling. It just passed a smog test easily for the DMV. So if it passed the smog test easily how could it be emissions related? Should I just ignore it like I have been? The auto service place that did the smog test did not seem overly concerned about it, but wanted $45 to check the problem on the computer.


When you had it smogged, was the light on?


Customer: replied 7 years ago.


Whoa. Really? I'm an inspector here in Rhode Island, and on our machine, if that light is on for ANY reason, its a Fail. Guarenteed. If that light was on during an inspection test, then I would strongly suggest it's a "minor" sensor in the EVAP system. Without any drivabilty issues, its definitely in the EVAP system. For now, it's ok to ignore, but like i say, if you'd like to have it checked for Free, AutoZone is the place to go. Once you get the "p-code" you can bring it here to us, and we can give you the possible causes. But if it passed an inspection test, and you see no issues, i wouldn't sweat it.


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