[FIXED] GM Security / High Speed Network Concerns

2003 Saturn Vue 3.0L

Customer complaints

Stalling, no start. Intermittent.

DTC's

ECM
P1629 - Theft Deterrent

This vehicle was towed in, customer stated they thought it needed a fuel pump. After looking into on a scan tool, customer informed me a used BCM, ECM, possibly other parts have been replaced.

Symptoms

If I'm looking at ECM data when it stalls I lose communication with the scan tool. I've been looking at BCM data when it stalls and I still maintains comm. Driving at higher speeds (45mph) the security, engine, and service lights come on the dash, I lose throttle response, but then the lights go off and I regain control of throttle. The vehicle seems to only stall at low speeds (5-15mph) or while idling.


I thought I fixed this thing today when I found a completely unattached ground strap by G107, supposed to be attached to the ECM case according to the wiring diagram. It is the only ground at the ECM, but it is still grounded through the fasteners holding ECM to the engine I assume. And the condition is still present.

I'm looking to scope high speed data lines tomorrow to hopefully see something. Maybe get ahold of a Tech2 to look at some BCM anti theft data. Any other suggestions?

www.revbase.com/BBBMotor/Wd/DownloadPdf?id=67178


first id check the 2 grounds at the dlc. just to rule them out. 2nd id go to the bcm on serial data pin and check that see if it does something funny when it stalls. should be a 0-7 volt square wave. while watching the can lines see if they do something funny. as i see there are 2 networks on this car.

An immobilizer problem WILL NOT shut down a running engine. Yes, it mayl cause a no start but not a shut off situation. .....

That said you maybe dealing with another or 2 different problems.

Ok this thing is kinda sending me on a loop. I got so involved with the p1629, saw on live data in the BCM that the "key learned" parameter read no.

I called a buddy of mine over to the shop today with a Tech2, we got the key programmed, and now the code isnt coming back. But its still stalling. Ha. So I've looked at some data lines on the scope, didn't really pick out anything.I put the CKP signal on the scope and it didnt seem to cause the stall. I'm still concerned about losing ECM comm every time it dies, but I will be looking at 5v Ref and I want to find out if I'm losing inj pulse or possibly coil turn on. Joy

The car is FIXED with a used ECM. Injectors were being shut down, throttle plate was being de-energized. No codes, no power or ground dropping from ECM. I checked everything I could think of. Was'nt 100% confident in the diagnosis, but it worked. On to the next one

So did it work ..?