95 Riv P0341 SES and Trac Off lights

[Gondawannaland]

ARGGG!!!! OK, I have months into this car. I know I am not the only person inflicted with this issue, but I have not seen anyone post an actual fix even though I have scoured the Web looking for one.

A little background, I have over ten years in working as an Engineer on Engine Management System and in my younger days (mid 80's) was and ASE certified mechanic. I have had consultation on this vehicle with people that have a combined experience of over 100 years in EFI Engineering and 50 years as Automotive Technicians. And at this point we are all stumped.

Here is my problem: Traction Off/SES light come one. When on the engine idles slightly rough. Code P0341. This started as a rare occurrence since I bought it (6000 miles ago) and has progressively worsen over the past 8 months. Now, it will occasionally not start. I drove it before everywhere, now I don't trust it.

I have searched forums and seen folks with this problem, but I have not read of any real resolution. Also, it seems this problem is unique to Rivs and maybe only the 1995.

I bought the 95 Riviera 3800 SC with 150,000 on it and fixed a number of issues. Now the only problem left is the random SES/Traction Off light. Sometimes one, sometime both. Using a GM Tech 2 I see a consist P0341 code (by the way, a normal OBDII will not work on the 1995 since is used UART serial data and not the OBDII Class 2 serial data, this is why the Autozone tool does not work). I have occasionally had other codes in history, but that is probably from me plugging and unplugging almost everything under the hood. Also, the RPM on the tech 2 does not seem to indicate a random Crank Posistion Sensor error. I do see the “CAM/CRANK ERROR” counter increase. Usually 1 count on the initial crank, and then (if the code is going to set) about 10-20 counts every 5 seconds or so. As I said, the whole thing is random, so this is only the typical readings. Sometimes the light(s) never comes on and it runs great (although this happens much less frequently than it used to).

I have used a DVOM to check every relevant wire from the Cam Phase Sensor to the Ignition Control Module to the engine connecter (above the rear bank) to the ECU. Multiple times, including wiggling wires. Everything looks as it should.

The way the code is set is the PCM (or ECU) counts the number of cam pulses and compares to the number of crank pulses. It should be 6:1 ratio. If it miscounts it records a “CRANK/CAM ERROR”. After a certain number of these, the code P0341 is set (I think it sets at 10 errors). It should be noted, the PCM gets the CAM and Crank signals from the Ignition Control Module (ICM) not the sensors themselves.

I used a scope on all the circuits associated with the code (per Alldata) at the PCM.The scope does show some electrical noise on CKT 630 (Cam Signal) at the PCM. I THINK this is causing the problem.

I have replaced the following with NO impact on the performance: Ignition Control Module, Cam Position Sensor. I have cleaned the grounds at the ICM and I have cleaned many of the terminals.

The only things I have done that has seemed to reduce the problem (not eliminated it) was: A) putting a capacitor on CKT630 (marginal improvement) and B) running good shielded wire for CKT630 from the ICM to the Engine Harness Connector (pretty good improvement at first, now it is back with vengeance). By the way, I have moved wires, plug wires, unplugged the alternator, etc.... none has helped.

I am looking for information. Of course, I would ideally like someone to tell me a solution for the exact same problem, but in leu of that please let me know the following if you had this problem.

1) What have you replaced, and what effect did it have?

2) Please pull a spark plug and give me the exact make and part number from the plug if you have this problem and cannot cure it. (I am starting to guess plugs that increase electrical noise with age).

[mellowde100]

The one thing you didn't do was physically check to see if the interrupter was still in place. It is held by plastic and can fall out. Engine will still run but not well.

[Tech II]

Like Mellowde100 said, did you check the magnet, and and the CIRCUIT, from the sensor to the ICM.......

Surprised you are having such a problem testing since it is an easy circuit to test......you check for power and ground to the sensor......then, basically, you slowly rotate the engine manually(key on, injector harness disconnected, for safety).....while doing this, you back probe the sensor output wire with a multimeter at the ICM.....you should get a reading of 5-7 volts constantly, until the magnet in the cam passes the sensor(hall effect).....when it does, it pulls the signal low to zero volts...but as soon as it passes the sensor, it goes back to 5-7 volts....this is the trigger signal to the ICM, which is modified and sent to the PCM which knows now when to fire the injectors, sequentially.....without that signal, there is a one in six chance, that the injectors are firing correctly in time, and could cause a rough idle.....if the magnet is damaged or missing, that could be your problem......remove the sensor and using a mirror and light look for the magnet on the cam as it passes the hole where the sensor was, by manually rotating the engine....it takes two complete rotations of the crank for one turn of the cam.....

If the magnet is there and is ok, and you do get a switch in voltage as the magnet passes the sensor, as I outlined in the previous test, and you have done a drag test on the harness connectors at the Cam sensor and ICM, since you have put a new ICM in(I know, we are assuming it is ok), then the problem is between the wiring of the ICM and the PCM......have you checked the PCM? Not sure of the location....is it under the dash, or in the air cleaner housing? If in the air cleaner housing, and have you checked it? They are known for mouse nests.....suckers like to eat wire.....

If the wiring to the PCM is ok, then an ohm check will be necessary between the ICM and the PCM circuit.....if ok, then you have a possible PCM problem....