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Post by rcxtony on Jul 3, 2018 13:08:45 GMT -6
2002 3.5L with 180,000 miles now. Problem started last summer when for no apparent reason the tach would jump to 8, 000 rpm. Idles at 4000. Actual rpm's seem normal. After the shop replaced crankshaft sensor all seemed fine for about 3 weeks. Long story short, problem got worse over time, just replaced transaxle, back to square one. Recently discovered it happens within a few minutes of reaching temp and if I turn off the car off and then restart it, tach goes normal and issue does not return for rest of trip. Any ideas? :confused:
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Post by rcxtony on Jul 3, 2018 13:36:03 GMT -6
Sorry posted wrong spot since this is a 2G. Oops.
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tigger
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Post by tigger on Jul 3, 2018 13:58:09 GMT -6
Moved your thread to 2nd Gen Mechanical Maintenance.
Sure sounds like CKP sensor...
Do you know what brand your mechanic used? Some of the cheaper ones don't last very long.
Also, check the wiring and connector for any damage.
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Post by rcxtony on Jul 3, 2018 15:08:58 GMT -6
Sure sounds like CKP sensor... Do you know what brand your mechanic used? Some of the cheaper ones don't last very long. Also, check the wiring and connector for any damage. No idea what brand was used. Did however clean connector and check wiring to the sensor... all appeared fine. All I can do at this point is replace the sensor myself (unless my new mechanic can squeeze me in) and hope for the best.
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Post by phewop118 on Jul 3, 2018 21:11:57 GMT -6
Did your mechanic do the ckp variance relearn procedure? The procedure is activated by the scan tool and requires revving the engine to certain rpms for a period of time
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Post by rcxtony on Jul 4, 2018 14:50:53 GMT -6
Did your mechanic do the ckp variance relearn procedure? The procedure is activated by the scan tool and requires revving the engine to certain rpms for a period of time No idea... they sure charged me enough if they didn't. Is it required for the 3.5L?
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Post by phewop118 on Jul 4, 2018 22:05:40 GMT -6
Yes, it's required anytime the sensor is removed, even if the original one is reinstalled.
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Paulaurora
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Post by Paulaurora on Jul 5, 2018 6:18:40 GMT -6
TPS sensor or the TB need to be replaced . Main issue with 3.5 the gasket btwn engine and TB is getting bad and coolant can escape and cause sensor to stop working . And yes generic sensors will cause issues as well. SO better get ACdelco
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Post by rcxtony on Jul 5, 2018 7:16:09 GMT -6
TPS sensor or the TB need to be replaced . Main issue with 3.5 the gasket btwn engine and TB is getting bad and coolant can escape and cause sensor to stop working . And yes generic sensors will cause issues as well. SO better get ACdelco Ok... the problem I am having with understanding/believing any advice is the fact that I can predict exactly when the tach will flip out... and it only happens one time in my daily 60 mile trek. It happens within +/- 2 minutes of the vehicle reaching temp. Pull over, shut vehicle off, start it up again and go. No issues for rest of trip. Rpms, speed, up hill, down hill, nothing matters. I can sit in park at idle and wait for it to come to temp... put it in drive and boom. Tach freaks. Shut off, start and go... no issues.
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Post by phewop118 on Jul 5, 2018 14:15:08 GMT -6
That's really symptomatic of a ckp sensor problem. Do you have a hesitation or stutter if you are on the throttle when this occurs?
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tigger
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Post by tigger on Jul 6, 2018 0:41:02 GMT -6
Did your mechanic do the ckp variance relearn procedure? The procedure is activated by the scan tool and requires revving the engine to certain rpms for a period of time No idea... Is it required for the 3.5L? Yes, it's required anytime the sensor is removed, even if the original one is reinstalled. Not to muddy the waters but, several of us here have changes out CKP sensor(s) without doing the relearn. ...Without issue. The PCM will relearn on its own. rcxtony, is the erratic tach the only issues? No stalling, rough idle, etc.? Just saying, you are throwing 2 CKPS codes...
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Post by rcxtony on Jul 6, 2018 4:49:49 GMT -6
No stalls, idles fine. If I am doing highway speed when it happens there is a noticable rough shift when the tach goes. But shut off/restart and all is fine for the rest of trip. The MIL lamp is always on with the 2 codes. The next time I can get it in the shop I am definitely asking about the relearn procedure.
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Paulaurora
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Post by Paulaurora on Jul 6, 2018 6:00:38 GMT -6
Yes most of the time no need to le learn but i have Tech 2 and i had to do re learn for one person in this forum after re learn car was better
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Post by rcxtony on Jul 18, 2018 4:45:58 GMT -6
Goes in the shop the 30th for relearn... we'll see.
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Post by rcxtony on Aug 1, 2018 18:11:07 GMT -6
Goes in the shop the 30th for relearn... we'll see. And it came out of the shop with no change... another 60+ bucks and I still have a p0335 and p1336 or whatever code. Runs fine til temp when the tach goes coblooey, shut it off/start it up again and all is fine!
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Post by rcxtony on Aug 1, 2018 18:21:33 GMT -6
Goes in the shop the 30th for relearn... we'll see. And it came out of the shop with no change... another 60+ bucks and I still have a p0335 and p1336 or whatever code. Runs fine til temp when the tach goes coblooey, shut it off/start it up again and all is fine! Ok... 0335/1372. Crankshaft sensor problem. Did the relearn and code relearn code disappeared. But I still have the 0335 and 1372 codes lighting the check engine light. Car runs fine before and after temp... just have to pull over and shut the vehicle off, then restart it when the tach goes cablooy.
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Post by rcxtony on Aug 1, 2018 18:26:20 GMT -6
And it came out of the shop with no change... another 60+ bucks and I still have a p0335 and p1336 or whatever code. Runs fine til temp when the tach goes coblooey, shut it off/start it up again and all is fine! Ok... 0335/1372. Crankshaft sensor problem. Did the relearn and code relearn code disappeared. But I still have the 0335 and 1372 codes lighting the check engine light. Car runs fine before and after temp... just have to pull over and shut the vehicle off, then restart it when the tach goes cablooy. Guess its time to call a gm mechaniic and schedule a 150 mile drive.
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Post by rcxtony on Aug 1, 2018 18:29:57 GMT -6
Ok... 0335/1372. Crankshaft sensor problem. Did the relearn and code relearn code disappeared. But I still have the 0335 and 1372 codes lighting the check engine light. Car runs fine before and after temp... just have to pull over and shut the vehicle off, then restart it when the tach goes cablooy. Guess its time to call a gm mechaniic and schedule a 150 mile drive. Er.... 300 mile drive. 150 miles each way. Maybe I should take some vacation time while I'm at it.
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RCA1186
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Post by RCA1186 on Aug 2, 2018 6:40:34 GMT -6
Shot in the dark, I'd inspect the ignition control module and wiring for breaks and cracks. It is part of the CKP circuit.
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