Check engine light came on last week and the car started stumbling at times. I retrieved the codes and the important ones were 18 and 41. 18 is crank/camshaft error but if with code 41 -cam error disregard 18 and fix 41.

So I did the diagnostic routine and checked the voltages at the cam sensor at they were 10.5 volts and 7.8 volts. The 10.5 is perfect but the 7.8 is 0.8 volts high. Mmmmm I don't think that is a problem because the diagnostic routines only addressed low voltages. I chalked that up to OK.

Next I checked the voltage with the Key on Engine off at the ECM and it read 5.5 volts (had to bump it over to get it, which it said to do if was reading 0 volts) this was right on the money. Next test was Engine running voltage at ECM which should be variable between 5.8 volts and 5.4 volts cycling with a midpoint of 5.6 volts. When it is running fine (check engine light still on) the voltage is reading right. When it stumbles and the RPM goes up to 1500 (because of IAC compensation) I notice the voltage is not cycling or cycling too low (5.3-5.5 volts).

The routine says to check the wiring for continuity from the ECM to the ICM which happens to be 0.6 ohms (good enough). Thats it done. What now the check engine light is still on and it stumbles with those codes. I am suspecting the ICM so I pulled it off and cleaned the ground contacts and check ground...all good. I am now stuck on whether it is the ICM or the sensor itself. I don't suspect the balancer being damaged because that would show up all the time. I checked Canadian Tire for an ICM (ignition control module) and they want $270!!!! The sensor itself is only $46 bucks.

I had this problem years ago with my mother-in-law'* 1990 Bonneville SE and just went right to the sensor and changed it. Didn't do a damn thing and it ended up being the ICM, but there was no output from the ICM to the ECM.

Anyone else had this problem and can shed light as to their course of action because I am a real stickler on throwing parts at a car.

Thanks.

Some good suggestions here but I decided to go on my own....

My gut instinct was the Ignition control module - 280 bucks but for the $60 I decided to try the sensor. Changed it and nothing changed. Oh well I now have a new camshaft position sensor. I went back to NAPA and got the ICM and a deal (50 bucks off) and now it is fixed. It seems so odd that the module would go so slowly. It really felt more like a sensor going bad. Usually a module will simply quit working. Hey, I am just happy it is fixed because I am going to sea for the month on monday and the car wasn't working for the wife....a little tension if you know what I mean!!!

before you replaced your control module was your car cutting off sometimes?

Well, it was a 50/50 gamble. Great description of troubleshooting/diagnostic, very interesting. Glad you're up and running again. Better get ur sea legs ready for Monday.

No never actually stalled. When it looses the camshaft signal all of a sudden it will reset the fuel injector sequence resulting in a stumble and if you are laying into the gas, a very large pop and severe stumble