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What triggers a cel?

Old 04-17-2009, 12:14 PM
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What triggers a cel?

Would the following trigger a CEL?:

vaccuum leak?
bad TPS?

thank you
Old 04-17-2009, 12:42 PM
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Vacuum leak= probably not

Bad TPS= yes.
Old 04-17-2009, 01:15 PM
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something wrong
Old 04-17-2009, 02:01 PM
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After 02 senors, vaccuum check, plugs and wires (and a failed emissions).. the truck is still idle jumping and running poorly.. I thought I had it nailed but its back!!! So I have been reading alot about TPS's and thought I would inquire.. So if the TPs would trigger a CEL, and I dont have a CEL on, then Im cool?? I even rana scanner and pulled code 21 and 27..hence the 02 sensor changes... but nothing showed up about a TPS..

any thoughts?
Old 04-17-2009, 02:09 PM
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Is your coolant full? When the idle in my '93 22re was fluctuating, it was due to low coolant.
Old 04-17-2009, 02:21 PM
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There are several things but mostly anything that has an input to the ecm can set off a CEL.
Old 04-17-2009, 03:28 PM
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Code 21 and 27 are.....?
Old 04-17-2009, 04:48 PM
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Originally Posted by yota4life6
... So if the TPs would trigger a CEL, and I dont have a CEL on, then Im cool?? ...
You may be cool, but you can't really diagnose your problem that way. The computer is very smart, and if a sensor is way out of whack it will give you a clue about where to start looking. But the lack of a code only tells you that things haven't gotten so bad yet that the computer is complaining.

For instance, if your only TPS problem was an intermittent idle-position condition, I don't think that would throw a code. But it might give you loopy idle.

So you still have to be systematic, even if the computer doesn't know yet that you've got a problem.
Old 04-17-2009, 06:16 PM
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Originally Posted by DeathCougar
Code 21 and 27 are.....?
Basically:
21- faulty heater circuit on primary O2 sensor
27- faulty heater circuit on sub-O2

I already commented on this on his other thread: https://www.yotatech.com/forums/f116...e-help-179698/

Last edited by abecedarian; 04-17-2009 at 06:18 PM.
Old 04-18-2009, 10:58 AM
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went back to emissions this morning after all that work done..failed bad!!! Legal CO limit is 1.20, I was 7.89!!!!!!! What in the hell is going on? Anyone know what that level is 7 times what it should be? the truck aside from the idle jumping from time to time, runs well.. What can I do to pass emissions????

thanks
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