Cam Position Sensor Blues - 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 02-05-2009, 11:48 PM   #1
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Default Cam Position Sensor Blues

This is making me crazy. I have been getting P0341-2 for 2 months now on the '95 SE. "Ignition problem" and "intermittent cam position sensor signal".

Checked for, and cleaned the little cylinder magnet interrupter on the cam.
Replaced the cam position sensor. (new, just in case)
Replaced crankshaft position sensor (new)
Replaced the wire harness that goes from the two sensors to the Ignition control module.
Replaced with a used, but definitely working ICM, cleaned it and all of the areas involved.
Replaced with a used, but excellent reading set of coils.
Checked and cleaned and reconnected the battery cables so many times, I dream about them at night. The scantool tells me the battery is running between 13.9-14.1 volts.

Just looking at my notes..

When the CE light comes on, I can clear it by turning off the car and restarting. P0342, which is the fatal error, clears. Leaving P0341. Sometimes, I'll drive 15 minutes and the CE comes back. Sometimes I'll drive for a few hours before it comes backs. My scantool doesn't give me a freeze frame on OBD1, so I can't figure it out from there.

This just smacks of being something electrical, just a quick short. It happens so fast. If i clear the codes with the scantool and drive around reading the codes every few minutes, there is nothing, then the two codes appear at once.

It started to happen a couple weeks after I replaced the water pump. There was antifreeze involved. So one direction I can go is the belt (which is a gator but could have gone soft), alternator, and battery. The other direction is the harness that heads towards the PCM and wherever else (and that looks like a pain to find and follow them). From searches, usually if the PCM is whacky, it throws more codes than just those 2. Only these two have been involved. I would just deal with it, but when the P0341 comes on, the PCM has the injectors doing some averaging thing and the car isn't as smooth or quick.

Will Rice Central be able to pick up something in a quick test of the battery and alternator, when the problem only happens occasionally?

I need some direction. I've had 2 independent wrenchers check it out, and they didn't have any good ideas. the only other help left would be to have it checked by a dealer. I just hate to turn it over to the enemy after fixing everything for the past few years with help/advice from everyone here. It'* great car mechanically, i hate to lose her over something like this.

Any thoughts would be appreciated. thanks.


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Old 02-06-2009, 12:01 AM   #2
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Only thing that comes to mind right now is to check the wires around the sensors. Could be a small short, or possibly some corrosion in the plugs.
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Old 02-06-2009, 03:44 AM   #3
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Dan...

That'* what'* nuts. The sensors, sensor plugs, wires are all "new'. the odds on them generating exactly the same problem is remote. Short of spark plugs, plug wires, and whatever runs to the PCM.. I have replaced the entire ignition system.

That'* why I wanted to check if anybody had run into anything simple, which i have overlooked. Everything left for me is either expensive or a pain.


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Old 02-06-2009, 07:59 AM   #4
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Ok, tell me if I have this right.

You swapped a pump, and kapow..you got hit between the eyes. You've changed and checked all the wirring and sensors in that area, except one. The engine harnesses ground connection to the block. I'm not 100% sure in 95 where it is located, in 97 it'* next to the oil pressure sensor on the back of the block where the coolant could have run and corroded the connection.

You are definately chasing electrical and shouldn't let it win. If the ground doesn't help, I'd try to borrow or test a pcm just because I've seen them toss zero codes and cause issues..or 100 codes with no issues.
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Old 02-06-2009, 09:07 PM   #5
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Hey Boosty!..

The plot sickens. It was a couple of weeks after the waterpump change. I cleaned the lead on the engine block, BUT i only did it the first time with the cables. I hadn't checked back on it and I had been spraying cleaner and everything else on the accessory side while working on the sensors. Plus that area of the engine is a always a mess.

So I have the car on ramps and I'm checking the connection to the starter first. It'* still clean, but I notice the post and wire coming out of the low side of the starter is completely loose. (It was getting dark, so I couldn't follow it, it heads up and towards the opposite side of the engine from the battery. Cleaned it up, and wrenched it down.

Had to drive to neighbor'* and the store. The car runs much smoother (only I can tell) but the CE light comes on every few minutes. erase the codes, then they are right back. It'* not giving me P0342. Just P0341 twice, as a history error and a current cycle error. I thought the starter was completely cut out of the circuit, once the engine was turned over? And i haven't had any problem with starting.

Some good things.. now it does it frequently, so it could be picked up in an electrical system check. And now I can actually feel a stumble and micro-second slight drop in the lights when the code first hits, shortly after that the light comes on.

I'm figuring a few things tomorrow. Pull and clean every lead (including the block ground, again), Follow that line off of the starter. Release the belt and spin all of the pullys. One way or the other I'll probably replace the belt. there might be a slip spot.

Sorry to be so wordy. Just wanted to get it all out, in case anybody has some thoughts. I'm still not real swift with electricals.

Three years and it'* still fun learnin'.

Boosty, really good to see you are teachin' to many folks again.


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Old 02-06-2009, 10:28 PM   #6
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Take a good close look at the battery. I've seen batteries go bad inside causing intermittent lost of power
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Old 02-07-2009, 11:49 AM   #7
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Quote:
Originally Posted by Danthurs View Post
Take a good close look at the battery. I've seen batteries go bad inside causing intermittent lost of power
Dan....

Yeah, I have to go back to assuming nothing. The last thing I did (actually had done, I just couldn't get enough torque on the Harmonic balancer bolt) was the crank position sensor. And it wasn't the silver bullet I was hoping it to be. In my usual cheapo ways, I'll have the battery and alt checked at AutoRice. Even if that gives nothing definite, I'm going to swap the '96 SSE battery in for a test.

Work is slowww. It'* funny how ya always have money, but no time. OR ya have time and no money. Right now I'm in the "time' mode.

BTW, The Info and Tech boards you have been building over the past few months are great. Saw them for the first time last night and it'* good stuff. The text and photos make them childproof.

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Old 02-07-2009, 11:57 AM   #8
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Glad to here that. If there'* anything I can do to make it better, just let me know. Good luck.
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Old 02-10-2009, 06:59 PM   #9
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OK. It'* rage time. Had the battery and alt checked, 4 test cycles. Perfect. Now everything else has been replaced... plugs, wires, belt... that block ground bolt from the battery cable isn't going anyplace for a long time. I still get the P0341 as a history error, then as a current cycle error with the CE coming on.

ECM is the only thing left I can do, short of taking it down to the quarry and giving it a push.

Is there anything I should be aware of for an ECM swap. For a test, I have access to one that was on a '95 that got T-boned and popped the bags. Is that a problem.. like I'll hook it up and my bags will blow.

And do I have to swap the PROM, also?

Those are the only things I can think to ask. My Chilton has little on it and my FSMs for the '96 and '98 aren't always dependable for the 'tweener '95.

This is a good car with a lot of life in it and there is good reason I can't have it being driven around with the CE popping on.

Anybody with experience/thoughts on doing an ECM swap, would be much appreciated. Thanks.


charlie

Last edited by charliemax; 02-10-2009 at 07:08 PM. Reason: kan spell just can't tipe
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Old 02-10-2009, 07:02 PM   #10
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I seem to recall some ECM problems. I think it was Billboost that was talking about that. Try doing a search here and see what comes up. Bill is the guy to ask though.
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