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Check engine light

The check engine light of our 2002 Impala has come on several times over the past 20 months. We have replaced the gas cap and O2 sensor once and the catalytic converter and EGR valves twice. Recently a dealer said we needed a new catalytic converter and EGR valve. Our local repair shop (who’d done all the previous work) replaced broken vacuum lines and cleaned the EGR valve. Three days later the light is back on. I’ve lost faith in our local shop but I don’t want to replace the catalytic converter and EGR valve unnecessarily either. Any ideas what I can do to get this problem diagnosed and repaired correctly?

Go to an autoparts store that will read your codes for free. Post them back here along with engine size and miles.

So far I don't see a reason to question what your local shop did. If the vacuum lines were cracked, they needed to be replaced, if the EGR valve needed cleaning, then it needed cleaning.  It is a little late for us to tell now. For that matter we can't be certain that the dealer was correct.

Remember that error codes DO NOT tell you that the converter is bad and needs replaced.  They DO tell you that the computer has noticed something unusual going on with the data coming from the converter.  It could be the converter or a sensor or even a part not apparently connected to the converter.

  That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. 

Regarding warning lights:

  1. if the coolant temp light comes on, shut off the engine ASAP

  2. if the oil warning light comes on, shut off the engine ASAP

  3. if a FLASHING MIL/CEL comes on, shut off the engine ASAP

    ASAP means driving to the berm of the highway right now and not waiting for the next exit.

The engine is a V6 3.4 Liter. The car has 138,683 miles on it. I’ll have autoparts store check this week and post codes. Thanks for the help.