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Check engine light NEVER comes on

edited February 2012 in Repair and Maintenance
I have a 2000 Toyota Camry that has a unique problem. The Check Engine light NEVER comes on even when first starting the car. I have access to a scanner and know that the car periodically throws a catalyst code but the light never comes on. I just assumed that the bulb was burned out.

Today while solving a non-working clock issue I had to take the instrument cluster to get to the clock. While I had it out I decided to check the Check Engine Light bulb. It looked fine so I took I replaced it with a bulb that I knew worked fine. Again, nothing. The bulb doesn't light at all. About 4 weeks ago my timing belt broke while driving (thank god for a non-interference motor) and it threw a code for the camshaft position sensor but again the light never came on.

Anyone have any idea as to why the light never comes on?


  • I would be everlastingly thankful...Apparently you don't have to pass an emissions test so it's not an issue.. But if you just can't stand not having that light come on, you could purchase a new dash cluster and ECU ($$$$$$$$) and MAYBE that would restore the cherished CEL ....

    Your light should come on according to the above link when you set the key to the II position, along with other dashboard lights, and be the one light remaining on after a few seconds. If the rest of the lights come on, but the CEL doesn't, and if you bought the car used, the plastic display cover might have been painted with black paint to hide the light, a sneaky old trick to sell a car with a problem. Otherwise, honestly, I have no idea. I'd suggest using the scan tool on as regular a basis as you can manage.
  • I thought maybe it might be covered, so when I had the cluster out and removed the bulb I was able to very clearly see the symbol with daylight shining through. I know of that trick and thought that might have been an issue. But no.

    Although here in Virginia we don't have emissions tests we do have a yearly inspection and an illuminated MIL is cause for failure. So I not that worried about it, but would like to figure it out. With access to the scanner I can clear it before the inspection.

    Other than that issue the car runs great and still gets 34mpg on highway with 210,000 miles and the original clutch.
  • When turning the ignition switch to the run position the Check Engine light should come on. This is called the self-test mode for the computer. If the Check Engine light doesn't come on in the run position it means the computer failed the self-test mode and there's a problem with the computer.

  • When it comes time to sell your car, this feature is worth paying EXTRA for...
  • Caddyman, you certainly are full of useful and insightful wisdom aren't you
  • Thanks Tester for the useful knowledge! Very much appreciated!!!
  • Of course, there's also the small matter of wires. Those things in between the computer and the lightbulb.
  • edited February 2012
    You need to find out which pin on the connector to the engine computer is for the CEL.
    Then check for continuity from the lamp socket to the computer connector.
    Also one pin of the lamp socket goes to ground, check this continuity too.
    If all that checks out then it's a problem in the computer module (lamp driver).
  • Like others have already stated, the CEL light is usually turned on through the ECU which probably makes a ground connection inside the unit to turn on the lamp. You can check to see if there is voltage on the lamp lead going to the ECU. If there is about 12 volts on it you should be able to ground that point and turn on the lamp to verify the rest of the circuit is ok. If the ECU is causing the trouble you can purchase a rebuilt unit for a lot less money than a new one from the dealer. This is a fairly common trouble. I have fixed some in the past by replacing the lamp driver IC inside the ECU.
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