Mechanics

PONTIAC BONNEVILLE ENGINE PROBLEM

2003 Pontiac Bonneville • 174,000 miles

Engine cuts out intermitenly when it does engine light flashes on and communication to snap on solus scanner is lost. No codes are set when it cuts out seems like its loosing power to the PCM. Engine also quits intermitenly when it does a code is set for the mass air flow sensor and engine wont restart until code is cleared. I have replaced the mass air flow sensor, Battery, fuel pump and filter. Fuel pressure is 45 to 50 psi. Engine runs good most of the time


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Guest
February 16, 2013.



This is sounding more like a bad PCM.

Wrenchtech
Feb 16, 2013.
What is the best way to verify that the PCM is failing?

Tiny
Mccaw
Feb 17, 2013.
That can be very difficult because there is no way to prove a PCM is at fault. What you have to do is verify everything in and out of the PCM, including all power supplies, grounds and sensor inputs.

Wrenchtech
Feb 17, 2013.
I dont no if this helps but I replaced the PCM relay and the engine doesnt cut out any more. But it does still dies completly after about 2 miles becoming more frequent the more it is driven. Logging a code for the mass air flow sensor everytime and not restarting until the code is cleared. Once the code is cleared it runs fine until it acts up again. I have also noticed that if I keep a steady speed it will quit running everytime. But if I run it up to 60 mph let it coast down to 50 mph and then back up never staying at a consistant speed it will not quit running. When it does Quit running its like the key was shut off no miss, hickup, or ruff running

Tiny
Mccaw
Feb 18, 2013.
You are going to have to somehow determine which function drops out first at the split second as the engine dies as to spark, injector pulse, fuel pressure. It's not easy but that is the route that has to be taken.

Wrenchtech
Feb 18, 2013.