With this month’s issue theme being “Maintenance and Service Repair,” I felt there wasn’t much I could contribute on that topic. After all, I thought to myself, I am a diagnostician not a service tech! Boy, was I wrong!
I recently visited to a shop located about an hour from home that had a 2006 Jeep Wrangler with a 2.4L, automatic engine that shut off while driving and would not crank or restart. While en route, I noticed I was rapidly approaching the mileage of when my next service was due. How convenient, I thought! I could write an article describing how I do the maintenance on my own car and include a diagnostic story at the same time. But first, the Jeep.
The shop owner (who is also the lead technician) had determined the Jeep had a bad PCM, but wasn’t confident with his diagnostic skills enough to pull the trigger and purchase one, nor did he own the tools necessary to finish the job once the module was installed. That PCM needed to be programmed, but he had no way to do it. That’s why he called me.
As I was driving to his shop, thoughts were going through my mind of what maintenance should be done on my car and how they should be performed. I was approaching 150,000 miles, which in my book means all the fluids get replaced and the spark plugs would get replaced, along with the air and cabin air filters. I will be performing an induction system service, and I’ll inspect all the steering and suspension components, along with wear items like brake pads. I also thought it wise to ask this shop owner to please get my car on a lift (while I diagnose the Jeep) so I may see if there are any other things I might need.
I arrived and looked at the Jeep; I could read the PCM Module Information (showed this unusual P/N: 56044706AB.05), read data, read DTCs (four, all about failed control circuits), but could not have the PCM control the ASD Relay or have it perform any other bi-directional function when using Actuator Test Mode. The PCM would not ground the controlling circuits, yet there was less than .050 VDC on both ground circuits when back-probing the PCM connector while commanding activations.
|Module info - original PCM|
|Module info - PCM #3|
Within an hour I came to the same conclusion as the shop owner, but not before performing the network tests the DRB III allowed. The network tests verified communication with all the modules that were fitted to the vehicle and showed me any DTCs that reporting modules had stored. I do this to make sure there isn’t some weird network problem that might be the reason for the no-start complaint. Everything was fine with the network. I was confident installing a PCM would solve this complaint.
Thinking ahead, the shop owner had a brand-new PCM waiting for me when I arrived. I was almost giddy with how smoothly this was going and was already thinking of getting an early start to the servicing of my own car. I definitely jinxed myself by doing so!