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need "check engine" light help


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3 times in the last 3 weeks (below 20 degree weather here in Buffalo) my check engine light would light up, if i shut the engine off and immediately restart the car, it would not reappear. I have a 93 legacy.

No driveability problems, perfect ice cold starting, no change in gas mileage etc. Any ideas on what could be the problem? Is the computer smart enough to sense something going before it goes? thanks

 

also, is there a way of getting codes out without going to the dealer etc. I know I once found a page that let me find tranny error codes by counting lights.

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Originally posted by johnd911

3 times in the last 3 weeks (below 20 degree weather here in Buffalo) my check engine light would light up, if i shut the engine off and immediately restart the car, it would not reappear. I have a 93 legacy.

No driveability problems, perfect ice cold starting, no change in gas mileage etc. Any ideas on what could be the problem? Is the computer smart enough to sense something going before it goes? thanks

 

also, is there a way of getting codes out without going to the dealer etc. I know I once found a page that let me find tranny error codes by counting lights.

I don't mean to hijack the thread, but my wife's car (93 Legacy turbo) is doing something similar. Only it's not quite as cold here, and it just started today. I drove it tonight and it didn't come on. I read the codes, they are:

 

13 - cam angle sensor

21 - Water temperature sensor

23 - Air flow sensor

42 - Idle switch

 

If the cam angle sensor was faulty, the car shouldn't run (but it does). The others should affect running to some extent, but it seems to run fine. I'm assuming it's OK to drive for the time being. I don't know how old all those codes are either, so I'm thinking I will reset the ECU and see if it does it again.

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I haven't read my codes yet, when I looked under the dash i only saw one black connector. Will read my codes in the next few days, the light hasn't appeared for over a week now-it is 15 degrees warmer now (20 degrees F.)

ALSO: my air bag light has been on constantly for 3 months now.-ANY IDEAS why?

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Originally posted by johnd911

ALSO: my air bag light has been on constantly for 3 months now.-ANY IDEAS why?

I had this happen on a different car, a 1992 Dodge Stealth. The SRS (air bag) light would come on whenever the battery voltage was too low, and would not self-clear. A dealer could clear the code, but then the light would come on again after the battery was low again.
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OthercarisaFiat,

 

Reset the ecu and see what codes come back. Always do this when diagnosising so you can rule out any erroneous codes.

 

 

johnd911,

 

There are ways of reading the airbag computer too....which I'd probably recommend doing.....I'll have to see about getting the procedure.

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Originally posted by Legacy777

OthercarisaFiat,

 

Reset the ecu and see what codes come back. Always do this when diagnosising so you can rule out any erroneous codes.

I'll try that. If these codes are stored indefinitely, the cam angle sensor could be from when the timing belt broke 2 years ago. The others, I have no idea.

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OK, I cleared the ECU last weekend, and today the CEL came on again for a few seconds and went out. Car was cruising at about 25mph, warm engine, 4th gear, outside temp about 32. Only code that came up today is 42 = idle switch. Car appears to run fine.

 

What does an idle switch do? Is it important? Should I replace it?

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Idle switch is in the TPS sensor. You can verify the TPS ie idle switch is properly adjusted by following the test procedure in the following scan

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/TPS_testing3.jpg

 

If it is out of spec, adjust it, so it's in spec. If you can't adjust to spec.....you should most likely replace the TPS.

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