With many of today’s vehicles, the engine compartment is so jammed packed the battery needs to be relocated to other areas of the car. In some cases their relocation makes access to them difficult. In an effort to provide a reachable battery jump point, a remote jump stud is connected to the positive battery cable. These jump studs can be in close proximity to the vehicles Transmission Control Module (TCM) as seen in Figure 1.
There have been instances where the protective cover is missing from the jump stud and when vehicle repair requires TCM removal, the TCM touches the stud. This accidental short to power between the TCM and positive battery jump stud causes instant damage to the TCM requiring it to be replaced.
Obviously some observation is required to asses the safe and successful removal of any control module. In most cases it would be best to locate the battery and disconnect it from service no matter how inconvenient it may be.
Interestingly enough, I was recently at a shop to assist in diagnosing a 41TE transmission in a 1999 Sebring. It was experiencing 2nd gear starts in both OD 1st gear (Figure 2) and Manual Low (Figure 3) range without coding or defaulting to failsafe. As I was driving the vehicle with a scope and scan tool, it would take off in 2nd and shift up to 4th into full converter clutch apply perfectly. When coming to a stop, it would rarely make a downshift into 1st gear. When I returned to the shop I asked the tech assisting me to unplug the TCM as I wanted to make some checks related to both the solenoids and pressure switches.
The pictures in Figures 4 and 5 reenacted what took place moments later. The battery in this vehicle was not remotely placed. It was in the engine compartment right along side the TCM. Rather than disconnecting battery cables the tech just stared to unbolt the TCM. Within seconds the ratchet made contact with the battery cables while it was fitted to the TCM connector bolt. It was the sudden flash that caught my attention to what was going on. So I asked, “Did you just snap my picture?” as a slight bit of smoke dissipated into the air just slightly above the ratchet and battery post.
I know that in a shop everything needs to be done “yesterday”. The pressure of a car not working right after repairs, the customer needing the car, the center manager or owner wanting to get paid for the job seemingly leads to making shortcut judgments. I totally get it and in most cases it seems to work out. The down side is when it doesn’t as in this case. There were not only wiring issues that needed to be addressed, it now needed a new TCM. This incident occurred where the battery was easily accessible to disconnect. So you can imagine how quickly caution may be avoided with remote batteries that would require extra time to reach. This can be a costly mistake. Unless of course, you like taking pictures.