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| Check engine light but no code (Page 1/1) |
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Mickey_Moose
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JUL 22, 07:43 AM
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Ok, this one has me stumped.
88 GT, 3.4l HT crate engine - lately throws a check engine light while driving with AC on - however there is no code (checked as soon as the light comes on). If the key is turn off and back on, the light of off. It usually comes on about 10-20 seconds after the AC is turned on.
Car seems to run fine, although it occasionally stumbles when accelerating from a stop.
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olejoedad
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JUL 22, 02:49 PM
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Grab a scan tool and read live data and the stored codes.
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IMSA GT
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JUL 22, 04:06 PM
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I'm very little help here but since I had it happen to me with an overvoltage from the alternator and check engine light, when you turn the AC on, does your voltage drop too low? I don't know if that plays into your issue.
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Spoon
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JUL 22, 06:40 PM
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Take olejoedad advice. You'd be surprised at what's going on "without" triggering a check engine light. Ask me how I know.
Spoon
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"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
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Mickey_Moose
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JUL 23, 09:06 AM
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| quote | Originally posted by olejoedad:
Grab a scan tool and read live data and the stored codes. |
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Using a scan tool - there are no stored codes. Scanned shortly after the light came on (while still driving), no stored codes. Also checked again once parked, no stored codes (maybe scanner is messed up?).
I can read the live data, but really do not know what I am looking for - maybe as IMSA GT mentioned, maybe the voltage drops too low. I did notice that the Integer reading jumps around (will settle in at 128 when at idle), is this normal? Does go into closed loop, etc.
Probably need to be able to record the data - my tool does that, but not sure how to retrieve the info (have to look it up - old Auto Xray unit - like late 90's vintage).[This message has been edited by Mickey_Moose (edited 07-23-2023).]
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olejoedad
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JUL 23, 11:22 AM
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Does The light stao on or does it go out after driving for a while?
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Spoon
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JUL 23, 07:26 PM
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"Integer reading jumps around (will settle in at 128 when at idle"
Explain, are you reading milliamps or something else. Does the Ck Engine Light come on at any time when the air conditioning is OFF?
Try this. At "idle" turn on every accessory including heater on high, hi beams, wipers high, left or right turn signal, radio, rear window deicer, foot on brake and anything else to draw current. Allow to idle for few minutes and see if check engine light comes on. Check voltage at cigar lighter with meter or have a willing subject check it at battery. Observe amp meter and record data.
Note if wipers seem much slower or turn signals flash slower. Take notes on findings and post results here.
ps: Have you cleaned your battery terminals lately?
Spoon
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"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
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