LenAveryt

I got to find a replacement MOV. I want to make sure to protect the unit for the future. I'm thinking of making a crowbar circuit that will blow the main distribution fuse in the event of another issue like this. Though it will probably never happen again in my lifetime. The alternator was Factory OEM with the 193K miles on it.

I was able to repair the TCU! Woohoo! Had a reverse polarity protection diode that was bad as well. Its now shifting properly.

I was getting a P1605 P1605 indicates a communication fault between the Engine Control Module (ECM) and the Transmission Control Module (TCM). I pulled and disassembled the TCU, I found that a MOV, Metal Oxide Varistor, which protects devices against overvoltage. This was protecting the 12V to 5VDC regulator in the TCU, When I hooked 12V to the inlet side of the regulator I got 5.05VDC out, so the regulator survived. When I put the TCU back in and cleared the codes, no P1605 cam back. But unfortunately the shifting, or lack thereof, still remains the same. So I'm going to the salvage yard to hopefully find one out of the exact same year and model and hope it doesn't need any programming.

I purchased a 1998 Nissan Pathfinder from a friend that was moving into a Range Rover, Poor Guy! The vehicle is in excellent condition, everything worked, until 2 weeks ago. My stepson, who is not mechanically inclined, took it for some "errands" Later we had to have it towed home. When I started looking at the vehicle I saw that the Battery was swollen, and had ruptured battery acid everywhere. I pulled the battery, cleaned the engine bay and put a temporary battery in. The vehicle would not even try to turn over. Looking at the electrical schematics I found that Fuse 18 that feeds the Theft Warning relay ( Starter Cutout Relay) was blown. Turns out that there was a short from the Fuse Block somewhere to the N.C. relay contacts. So to try to start the vehicle, I jumped the Park/Neutral relay. This allowed me to start the vehicle. When It was running, I checked the voltage at the battery and it was nearly 19VDC! So the alternator shorted or something and overvoltaged the vehicle. I pulled and replaced the alternator. started and checked the charging voltage and it was good. 13.8 to 14.2V Then I turned to checking other items. All the turn signals and stop lamps were blown. Replaced all of those. I cut the shorted wire from the fuse 18 at the block going to the contacts of the Theft Warning relay and at the relay and ran a new wire. So now all that works as expected. Now I have Transmission problems. Park and Reverse work like normal. In drive, the vehicle starts off in 2nd gear. It will manually shift into first using the shifter. Once in second, it wont shift to third, automatically or manually. Also the tow button does nothing and nothing is displayed on the cluster. So I'm thinking that the voltage issues ether took out the TCM or there are blown shift control solenoids.