We have a '95 Bonneville, supercharged.
In short, the engine cuts every once in a while. It either will stumble for a few seconds then cut or other times it just cuts right out no warning. Other times too, it will set a code and stumble but won't die out. It can do these multiple times in one day and other times the car will drive without a problem for weeks at a time.
Also doesn't matter if we are stopped or at cruising speeds. It will set the codes P0321
P1361
P0341
(and 0171 ocassionally) each time it happens.



We have changed the computer several times on advice from a gm tech who said these ecm'* have a very high failure rate and that may be setting the codes and causing the problems. We have repllaced the ecm several times, all with used, and have gotton the same results with them all. So Im thinking of ruling out the ecm.

They have all given the codes

P0321
P1361
P0341
P0171 (Ocassionally)
P0740
P1567-Cruise control even thouigh we never use it


Also at cruising speeds on the highway, the torque converter will either remain unlocked when it should be locked or it will unlock randomly at a steady speed. It sets the code P0740. Agian this problem only happens sporadically.

Whats should we do now?

P0321 sets when there are no spark reference pulses coming from the ignition control module.

P1361 sets when there is no fuel control signal from the ignition control module.

P0171 sets when your fuel trim values are high, meaning that your engine is running too lean.

It'* hard to draw a conclusion from those three... Possibly you are having problems with the ignition control module or the connections to it, or maybe the camshaft or crankshaft sensors.

After reading the haynes manuel over and over we leaned towards the camshaft sensor as the likely problem. So we just replaced it since its fairly cheap and easy to do. While the sensor was off, we looked through the hole while we turned the crank, for the magnet on the camshaft but I don't think I saw it. Not sure what it was really supposed to look like? And anyway, if that was missing wouldn't it cause a consistant problem?

I can't tell you if it has worked or not becuase we are in the middle of replacing the master cylinder, which we keep getting one with a leaky piston and having to keep returning them.

What about the torque converter problem? Anyone know what could be causing the code and lack of lockup ocasionally? I have monitered the lockup with my scanner. It will operate normally most of the time. When it does start acting up it will either just not lock when its supposed to, or it will be locked and just randomly unlock according to the scanner and obviuosly the feel of it kicking out and the rpm jump. Also it doesn't always set a code. (P0740 )


And about the cruise control. It does not work and hasn't for years. So we never attempt to set it. So why do we always get a code for it (P1567) if we haven't touched it?

You are getting the TCC code because it is not locking up. Could be electrical, a bad solenoid, or maybe the torque converter is shot. What is the condition of the transmission fluid?

The cruise code indicates a problem with one or more of the switches, including the on/off/resume switch, and also the brake switch. There is incorrect voltage detected at the computer. That'* why the cruise doesn't work.

The fluid seems fine. No obvious odor or color change, foaming etc..... Fluid level is fine.
What are the steps for checking this torque converter problem? I don't have a shop manuel for this car like I do for my Camaro and I'm not too familiar with the converters on Bonnevilles. The Thanks

You need the Tech II or Tech I to be able to manually switch the TCC on and off. You need to eliminate all electrical possibilities, as this transmission is an electronic automatic one (controlled by the PCM), then you can blame one of the solenoids. The diagnostic in the dealer manual is somewhat complicated.