70+ Codes and a Total Mess!

OK, we admit, this one is a little longer than our typical resource reference. But, we really believe it is worth your time, as did many commenters on this post by Darren on Diag.net. As is often the case, this diagnostic tale starts with a non-running vehicle that has been seen/inspected/unsuccessfully repaired by several others (6) before reaching our author Darren. After several initial diagnostic steps, including getting background from the vehicle owner, Darren checks for codes and finds over 70 stored. He knows he’s up against it.

He then continues his process, including fully charging the vehicle’s batteries (2015 Malibu equipped with start-stop and two batteries). “After an hour or so, I attempt to crank and what do you know it fires right up. Now at this point I was not using my stop watch but not long after starting I hear the starter attempt to engage (mind you the engine is running) At this exact moment I also hear the engine rev up (just like a post start idle flare) This happens a few seconds later and again a few seconds after that where upon the engine dies. I scan for codes, get in some systems – U0100 and U0101 and a few other codes related to power (Short to B+ and to ground) and a few others. But, no communication from the PCM or TCM and no check engine light. I also get some interesting HVAC codes concerning VIN not programed and a security issue due to incorrect configuration of HVAC – interesting….” He then outlines his diagnostic process, starting big picture and, step by step, narrowing it down to the root cause of the problem. It is textbook diagnostic problem solving. We won’t give it away – check it out by clicking the link below.