CMP Sensor Intermittent Failure - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-30-2006, 05:29 PM   #1
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Default CMP Sensor Intermittent Failure

If this goes in 92-99 I apologize in advance.

So I am driving home from class today and the engine kinda hiccups. No big deal, its happened before. Did it a couple more times, and finally one more bad enough that it threw a code. Pulled over right away to make sure my new intake was intact (was hoping I wouldn't open the hood and find my RX-4750 collapsed in sucked into the intake pipe ). No problems there, got back in my car and the engine died. Crap. Went to start it, no go. Tried again and it started up. Drove 5 miles home and just had some minor power issues and hiccups and what not.

Got home, got some chow, got in my car to get the codes pulled. No CEL, no engine problems what so ever. Get to the shop, $35 later I have codes 321, 341, 361.

I don't see any codes like this in my Chilton'* (shoulda gotten a FSM). Here is the explaination from the shop. One of them is "Intermittent No Cam Signal." One is "EST" (??) and the other is unrelated.

So it could be my CMP...thats like a $40 part or so.

But then while there, the guy told me about a Bonneville that they had in there within the last month. Here is how I interpretted what he said. There is a magnet inside the timing chain housing which is either on the cam, or rotates with the cam...what ever. The CMP sensor reads this magnet. The magnet on the Bville they recently saw was loose. So sometimes it would sorta move a bit to the point where the CMP sensor couldn't read it. Either it did, or it could, eventually fall off. When this happens the car will die and it will not restart until it is fixed.

He said one of three things could happen. It could never happen again (but something similar has happened in the past, but not enough to throw a code), it could get worse and worse and happen more frequently, or eventually the magnet will fall of with no warning and leave me stranded.

He also said if it was the magnet it would cost $400, mostly in labor because they would have to take the "front cover" off of the engine.

I guess I am just curious, have you ever heard about this. I have never read about it on here before. I know all about the camshaft position sensor with the wires going bad, but never about the magnet on the cam. What gives?
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Old 01-30-2006, 05:52 PM   #2
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The cam shaft position sensor magnet is located on the cam shaft sprocket. The engine will operate if the cam shaft sensor fails, but will run in a degraded state due to the PCM not receiving that particular input for ignition timing etc.
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Old 01-30-2006, 08:49 PM   #3
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I would say that I experienced a loss of power (I'm guessing from poor timing) most of the way home, but with a hiccup every once in awhile.

How do I know which one it is? From the looks of it the sensor is like $40 if I do it myself, but the magnet is going to cost a lot in labor since I don't know how to take the timing chain cover off.
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Old 01-30-2006, 11:30 PM   #4
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Did you do a search cause ther is lot of info on it , Im like you Ill try anything but this job is a little overwhelming for the newer guys, but there are a few threads that will give you some incite.
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Old 01-31-2006, 09:26 AM   #5
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Logan..hang in a little .. I don't have any experience on that..

Except I can tell you from personal experience on S2 (I know..your are S1) there is a 1 in 6 chance the motor will start and run. That'* what happened to you on the side of the road. Took more than one try to fire up.

Once mine was running, there were no issues, power loss or anything in default mode. Ran fine. And on the magnet issue..I thought that was only the LN3 guys that had that issue.
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Old 01-31-2006, 01:08 PM   #6
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Quote:
Originally Posted by BillBoost37
Logan..hang in a little .. I don't have any experience on that..

Except I can tell you from personal experience on S2 (I know..your are S1) there is a 1 in 6 chance the motor will start and run. That'* what happened to you on the side of the road. Took more than one try to fire up.

Once mine was running, there were no issues, power loss or anything in default mode. Ran fine. And on the magnet issue..I thought that was only the LN3 guys that had that issue.
LN3'* and some L27'* will experience this issue... But the codes he has really looks like the experiences I had with my 95...



Bill you have the info on the codes for these?

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Old 01-31-2006, 01:12 PM   #7
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My manuals don't have 94. Going for techinfo.

Don't see it in techinfo. Will someone with the manual please post the info.
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Old 01-31-2006, 01:18 PM   #8
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321, 341, 361

Logan these codes are bothering me... I believe that they are actually

P0321 Spark Reference circuit

P1341 Cam Crank Error

P1361 Ignition Control Circuit.. It seems that you are running in Module Mode..

does the car Stall, miss and at times backfire?

I need a 94-95 manual on CD... There is a lot of info on these codes.. And the 321, 1341 may have something to do with the 1361... The 1361 bugs me as the PCM is not taking over the timming control leaving the car running of Module( ICM ) mode... when this happend the car will run like true Crapp...

Anyone have any thoughts?

The last time I had the 321 and 1361 at the same time I ended up with a new PCM, as it was not toggling to take over control from the ICM after 400 rpms...

We need to look into it a little more..

I was going to suggest something but just realized that you don't have a scantool..

BTW the code 1361 should have lit up the SES light like a christmas tree...

Eventhoguh you have an L27( 94 ) and I have an L36 ( 95 ) the PCM'* are the same and are controled in the very same manner( slightly diffrent programming )

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Old 01-31-2006, 01:47 PM   #9
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Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by BillBoost37
Logan..hang in a little .. I don't have any experience on that..

Except I can tell you from personal experience on S2 (I know..your are S1) there is a 1 in 6 chance the motor will start and run. That'* what happened to you on the side of the road. Took more than one try to fire up.

Once mine was running, there were no issues, power loss or anything in default mode. Ran fine. And on the magnet issue..I thought that was only the LN3 guys that had that issue.
But the codes he has really looks like the experiences I had with my 95...
Which was?

I have _never_ had a backfire and I do not feel any missing. The car was running fairly smooth even after it happened, but it was not running normal. Its very important to note that it seems just fine now.
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Old 01-31-2006, 04:21 PM   #10
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Quote:
Originally Posted by Logan
Quote:
Originally Posted by jr's3800
Quote:
Originally Posted by BillBoost37
Logan..hang in a little .. I don't have any experience on that..

Except I can tell you from personal experience on S2 (I know..your are S1) there is a 1 in 6 chance the motor will start and run. That'* what happened to you on the side of the road. Took more than one try to fire up.

Once mine was running, there were no issues, power loss or anything in default mode. Ran fine. And on the magnet issue..I thought that was only the LN3 guys that had that issue.
But the codes he has really looks like the experiences I had with my 95...
Which was?

I have _never_ had a backfire and I do not feel any missing. The car was running fairly smooth even after it happened, but it was not running normal. Its very important to note that it seems just fine now.

I had a PCM fail( the factory unit ) in the 95 and got a code 321 and 1361

Swaped out the ICM with a known good unit and same story... Car would start, would run... Ses light would come on some of the time... It was freaky... I would start it once and it would run off color I would ge a miss or two and a light backfire from time to time... I finally replaced the PCM with a trunk unit( Don always has a trunk unit - Spare ), and what do you know car ran great, no codes and no SES... I have had one code sence then... And that had to do with the passkey system and didn't set off the SES... Never had the code come up again...

I was going to say if you had a scantool that would read the car, you could erase the codes or disconnect the neg terminal at the battery, leave it for a few minutes... You should have no codes once you reconnect the battery and turn on the ignition, then check for codes... if you have the codes right off the bat then chances are the PCM has bit the dust... For now keep an eye on it.. If it gets worse or happens again let us know

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