Hello everyone,


Ok, here is what I have. The car would randomly stall, then start again if you let it sit for awhile. I has now stalled and it won't start. I have tried the crank position sensor test and ICM tests. Here are my stats:

1. 3.8L
2. Fuel pressure: 45-50psi
3. No spark
4. Cranks over good
5. Battery new
6. ICM ground good, I cleaned up the 3 ground contacts under the hood also
7. 12V to ICM: I only get 1.48V when I probe the connected harness. However, I get 11.56V on the P wire when the harness is disconnected from the ICM and when the ICM/Cam/Crank sensor harness is unplugged from the main harness in front of the intake.
8. 12V to the Crank sensor: only get 1.48V when I probe that wire. I think it was the N wire, but I can't remember. I did probe the correct wire however.

I did some parts swapping off a 3.8 that runs but no luck. ICM harness, ICM and coils. I put the ICM/coils from the bad car to the good car and the known good car fired right up. So I am ruling out those parts being bad.


My #6 above is what has me stumped. Something is dropping the voltage when the harness is hooked up. I believe that is causing my No Start issue. But, I may be on the wrong trail also.


Does anyone have any ideas or had a similar issue?

Everything points to the crank shaft position sensor. Have you changed it yet? It is one of the most common failures we see with the 3.8 in the Bonneville.

That is what I was suspicious of, but the voltage test does not support that as the problem. Would the CPS cause the 1.48V input to the ICM when the harness is hooked up?

Forget your voltage tests. Change the CPS. Tell me if the following matches what you are experiencing:

• Engine randomly shuts off like someone flipped a switch. No stuttering or drop in power, just shuts off.
• When it first starts happening the engine is up to full operating temperature.
• First few times it happens it will usually start right up again, perhaps even before you coast to a stop.
• As time progresses, it happens more often, and takes longer rest periods to start up again.
• Gets to the point where it won't start even after resting for a while.
• When it won't start, there is no spark to any of the plugs, engine cranks strong and good fuel pressure.

I could probably think of more symptoms, but I hope you get the idea. For an '02 Bonneville with the 3.8 it is not a matter of if the CPS will fail, it is a matter of when it will fail. I can't begin to tell you how common this is for your car.

Yes, every one of those are the symptoms. I normally do every test possible to have good proof rather than change parts, but in this case I will try the CPS. I have seen many posts about that being an issue on the 3.8. Those are cheap enough and I was 95% certain that is what the issue was. Thanks for your replies. I will post what I find out after I get it switched out. I hear the balancer bolt is a "B" to remove. Any tips besides persistence?

Disconnect the battery.

Jack the front right of the car up, remove the wheel, and remove the passenger side front wheel well liner (two pieces) to get direct access to the bolt. Use a 1/2" drive socket wrench with enough extensions to extend the wrench out past the fender. Put a car stand (or something of the right height) under the extension right up next to the wrench to support it when you reef on the wrench, and use a FBCB (friggin big cheater bar) to turn the socket wrench. There is a small plastic access plate on the bottom of the engine at the interface to the transmission you can remove that will give you access to the ring gear (the thing the starter turns) which will allow you to stick something in there to stop the engine from turning over when you are reefing on the harmonic balancer bolt.

Once you get the bolt out you will need a puller to get the harmonic balancer off. If you don't have one, most auto stores loan them out (you place a deposit that you get back when you return the tool).

Before you remove the old CPS, mark its position with something and use that as a guide to line up the new one. There is very little adjustment when installing the new one, but there is some slight movement so you want it in the same position as the old one. Inspect the inside of the harmonic balancer for any cracks, broken or missing pieces, or any other problems.

Technically, you should use a new bolt for the harmonic balancer when you re-install it.

The only difficult part about this repair is removing the harmonic balancer. Get all your tools in place before you start, take your time, think before you act, and you should be okay. Make sure you have a jack stand under the car, as well as under the socket extension. I have done it several times with just basic hand tools.

Also, take a picture of old CPS before you remove it to be used for comparison when you install the new one.

Of course, the whole procedure about the extensions and the FBCB is made simple with an air compressor and an impact wrench.

Here is a good thread to read:

https://www.gmforum.com/mechanical-1...sensor-279066/