TCU Issue, please help.

[metzroth]

I am having a TCU issue that is causing the leaf to throw the yellow EV light on. Here's the DTC codes...

P312A 00C0 EV/HEV Comm Error EVC-208
P3131 00C0 EV/HEV System Shutoff Timeout
P31C2 00C0 EV/HEV TCU EVC-273
With a current code of....
U1000 000B TCU CAN Comm Circuit

My understanding of all this is that either the TCU has lost it's "activation" or is stuck on. Please confirm that understanding as well as offer any suggestions... like go to this area of the car and unplug the ^&*% TCU module . My leaf has 106,000 miles on it and I don't want to go pay Nissan $149 just to unplug the TCU, re-activate it, or tell me I can pay them $350+$149 to fix it.

[Stanton]

2 questions:
1) did you upgrade to the 3G TCU?
2) have you read the (very long) upgrade thread...which contains just about everything you want to know about the TCU?

[metzroth]

2G upgraded to 3G in April 2016. Reading the threads, the first thing I’m going to try is unplugging the grey wire harness from it and see if the yellow warning light will disappear. While I’m under the glove box, I’ll change the cabin air filter as well since I’m already there

[cwerdna]

Just pull the fuse for the stereo/audio system under the hood to get the TCU unstuck. To mitigate the issue that seems to cause the P3131 DTC and the yellow ! car, see below.

viewtopic.php?p=515624#p515624
viewtopic.php?p=516453#p516453

Supposedly NTB18-045 addresses these probs. See viewtopic.php?p=531975#p531975. Unfortunately, I haven't seen the PDF of the TSB myself nor do I know if it's really effective yet. Will probably get it done in the near future.

[Lothsahn]

Or follow the instructions here to disconnect the TCU entirely:

viewtopic.php?f=27&t=25949&p=528909#p528909

Note: this is for the 2G model but the 3g should be about the same.

[Supersleeper]

IDK why, but I've been having more issues lately. About once a week now, where before it was only about once a month. I really wish there were an easy and permanent fix to this. I'm about to go and find the actual +12v supply to the TCU harness and install a toggle switch. Sometimes pulling the fuse doesn't solve it, and I'm tired of pulling the battery terminal, resetting the clock, and everything else.

Another thought was to just go and find a extremely low-power timer circuit that will automatically kill the power to the TCU once every few days for about 2 min.

[LeftieBiker]

I'm about to go and find the actual +12v supply to the TCU harness and install a toggle switch.

That was my suggestion, last year. I'd just turn the damned thing on when needed, leaving it off otherwise.

[Supersleeper]

I'm about to go and find the actual +12v supply to the TCU harness and install a toggle switch.

That was my suggestion, last year. I'd just turn the damned thing on when needed, leaving it off otherwise.

I’d always forget. But I was also thinking, maybe something more clever. Maybe have a relay staged off of accessory, so that when you shut off the car, it would momentarily power-cycle the TCU. You could do this with a simple relay, and 12v Super capacitor. The capacitor would draw current off of the relay when accessory is lost, momentarily keeping the relay triggered to break the circuit. Then once he capacitor is charged, the relay would then close the circuit.

This way, you’d always have a fresh system when you leave the car.

[baustin]

IDK why, but I've been having more issues lately. About once a week now, where before it was only about once a month. I really wish there were an easy and permanent fix to this. I'm about to go and find the actual +12v supply to the TCU harness and install a toggle switch. Sometimes pulling the fuse doesn't solve it, and I'm tired of pulling the battery terminal, resetting the clock, and everything else.

Another thought was to just go and find a extremely low-power timer circuit that will automatically kill the power to the TCU once every few days for about 2 min.

What is the state of your12v battery? The 3g TCU is more sensitive to the voltage level than the 2g unit was. Since I replace the original 12v (over 4 years old) with a AGM style battery, the number of times the TCU had to be reset dropped considerably. Now, I only need to do a fuse pull (about 60 seconds) once every two to three months.

[Supersleeper]

It’s a brand new gel cell.