TCM Fuse Repeatedly Blowing

[Ravenhide]

So, I'm stuck at work right now, 45 minutes away from home at 1 in the morning. Got off work at 11 pm, started my Aura, and got an illuminated MIL and a Power Steering warning on my dash. No biggie, I'll just add some fluid. Quick Google search and I discovered the Aura XR doesn't have a hydraulic system, it's electrical. Well, frick. Battery connections are solid, battery seems to be fully charged. Well technically according to my meter the battery is at like 17.5. Seemed a little high, but car started and ran just fine. Decided to check my fuses with my meter, and bingo! Fuse 42, the 10 amp for the TCM is blown. This matched my OBD II, which told me that the MIL was illuminated due to communication loss with the TCM. So cool. Found the issue. Car has 128k miles on it, I've never replaced any of the fuses since I got it via a buy here pay here program at like 108k miles. Since every place is closed and my workplace doesn't sell fuses, I scavenged a 10 amp from my heated seats so I could attempt to get home. Except as soon as I turned the ignition the damn fuse blew again.

So, now what? I have no idea how to check my wiring, grounds, or the TCM itself to try and pinpoint what's causing it. I don't even know where my TCM is. Google suggested it was at the base of my steering column but I haven't tried to look because I have no idea what I'm even looking for. I'm open to any suggestions at this point, although it's likely I'm going to be spending the night in my work's parking lot. I dont get paid till early Wednesday morning so I can't even tow it to a shop and have them take a look tomorrow. Any help would be appreciated at this point.

[fdryer]

17.5vdc is 2.5 volts higher than it should. Max is 15vdc. As voltage goes higher, possibly from a runaway regulator in the alternator, higher voltage will push current into everything, and cook wiring, electrical items and electronics. Guess how I know?

A runaway Ford external voltage regulator made the alternator output 20vdc and cooked a new battery. The alternator was too hot to touch. Battery was replaced under warranty and a new voltage regulator fixed the runaway voltage above 15vdc. 15 volts may be seen for a moment or so on freezing cold engine startup as the battery needs recharging and freezing temps lower battery voltage. Normal alternator output is between 13.5v-14.5v.

Be sure to monitor battery/alternator voltages, not exceeding 15vdc. Continued higher voltages will burn out lights, relays, and stress electronics that are designed to operate as low as 9 or 10 volts (subfreezing temps at startup) to 15 volts.

The blown tcm fuse may be either a short in one of the valve control solenoids operating gear shifts with hydraulic pressure or higher voltage pushing current into the tcm and simply blowing one fuse.

L300s have their TCMs on the passenger side windshield cowling. A large wire harness runs along the top of the firewall and makes an entry into and under the cowling. Your tcm may share a similar wire harness and located in the same area or elsewhere. L300s have the 3.0L V6 engine with a pair of ecm wire harnesses connected to the ecm on the engine driver's side of the intake manifold. The ecm and tcm harness are similar sized so it may be easy to trace ecm and tcm harnesses in the engine bay.