Edmunds Answers



  • brettl 10/18/08 8:42 pm PST

    You don't name the vehicle or give many particulars, but most of these 'check engine' light situations are caused by malfunctions in the emissions systems, that can be caused for a myriad of reasons. Given that there are probably two coolant temperature sensors on or near to the thermostat housing, which might have been unplugged to necessitate the changing of the thermostat and which directly or indirectly control some of the other emissions systems/components, first thing I'd be looking for would be one or both of the coolant temp sensors not being plugged back together in the wiring harness at the plug, or a bad connection at those points. That's the easiest and quickest thing to look for and check.
    If that's not the problem, then pull the codes off the computer and that'll steer you in the right direction, at least.
    Incidentally, IF you find the problem in the wiring/plugs to the sensors as I mentioned above, your 'check engine' light might not extinguish until the engine comes up to operating temperature and the vehicle is driven at least 30-35 MPH for a short distance. Good Luck!


  • zaken1 10/18/08 8:42 pm PST

    The repairs would probably only cause the light to come on, if they knocked a sensor wire loose, or didn't put all the wires back on when they replaced the radiator. The light might also come on if there was an air pocket left in the cooling system, and the coolant level is now too low, or the engine is overheating. The coolant level in the radiator (not just in the reservoir) should be rechecked a day after the repair was done. I would take the car back and have them check to see if they left anything off, or if the coolant level has gone down. Don't let them tell you that the car now needs more work; just because the coolant level is now down. Have them fill it all the way up, and then see if it goes down again in the next few days. The check engine light can be reset by disconnecting the battery ground cable for longer than one full minute.

    I hope this helps!!!

  • tek1010 10/18/08 8:46 pm PST

    I think the answer to that is what code is set that is turning on the check engine light.
    Several parts store such as Advance and Autozone will tell you what code you have for free.LMS


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