Ahh, so the starter battery is on the car’s right side? That makes more sense to me as I thought I was boosting the aux battery when in fact I was boosting the starter battery. We should use the stage right/audience left terminology 😊Who said the TCU was in the right rear?
It is located on the left side, three mounting bolts, cable connections on the down side and the battery is on the up side. (Flip the ebay picture above 180 degrees.) Remove the little screw and the panel scene in the picture to get to its battery.
Perhaps confused as this thread was started about the auxiliary battery and a person standing in front of the vehicle looking in the frunk area would find the auxiliary battery on their right (car's left) side.
A question: is this battery open or short circuit faulted, or is there a blown diode or fuse or other fault between the battery and the TCU electronics? If the TCU is faulty and still under warranty, would it be voided if you change the wired in battery?WattCat was giving a correct reading of 0% on my TCU backup battery.