First, NEVER try to hunt down a problem by buying and replacing parts. As you can see, it gets expensive and hardly ever works.
The proper diagnostic procedure is to isolate each system and TEST the components until you find the one at fault. Then replace only that part.
Your Code 56 means the "Quad Driver" your computer uses to send voltages and grounding signals to sensors and other engine components is faulty. This is MOST CERTAINLY your issue.
Not sure if just the driver can be replaced or if your computer must be replaced. But these buick computers were definitely prone to failure. Sorry.
Sunday, November 28th, 2010 AT 12:21 AM