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2015 Leaf Method for Disabling TCU

Ok, I've followed what I believed were the instructions for disabling the TCU so my 2015 Leaf would work properly with the OVMS. I believe in doing so, I'm running into some side-effects caused by canbus errors due to this.

First, I disabled the TCU by removing the large white connector. This successfully got the TCU off the bus and OVMS was able to do remote a/c and charge successfully. I've seen some strange things happening with the car since doing this: door lock/unlock doesn't always work, I've had charge sessions go crazy and keep restarting on their own. I was suspecting these strange things were related to removing the TCU from the bus, resulting in bus errors and problems with the various modules communicating properly. Pulling DTCs pretty much verfiied that, as I had bus errors for several systems including the brake system, ev/hev, hvac.

This prompted me to do some further searching, and I discovered a page on disconnecting the TCU, but completely unrelated to OVMS. This page indicated that if you remove the white connector, you will get a bunch or codes for bus errors. It instead recommended removing the grey connector on top, which will disable the TCU but not result in bus errors. I've tested this, and it will only result in a single DTC for the TCU not communicating over USB. The unfortunate part is the TCU does appear to be powered up and communicating on the bus. So while all the other parts of the car now appear to be working properly and not having bus errors, the OVMS can't start the remote a/c because the TCU is working on the bus.

Has anyone looked at what is needed to get the white connector removed without causing bus errors? I don't know enough about canbus to know if those pins would just need to be terminated properly, or if looking for a power wire to disconnect would turn off the TCU but allow the bus to work properly. Anyone tried either?

If anyone is interested in

If anyone is interested in this, it is yet another means of disabling the TCU. I originally disabled it by removing the large white connector from the TCU, and found I had many bus errors (EV/HEV, BRAKE and many on BCM). I wasn't really sure how many would be related to the TCU as I think only one of the can-buses goes to it. Regardless, I tried for a couple weeks with the white connector installed and the errors didn't return.

So I'm now disabling the TCU by removing the power connections, while leaving the others (canbus) connected.

TCU White Connector

This is the view of the white connector (2015 model) looking at the 'wire side'. I cut the wires for pins 1 (Battery - white), 3 (ACC Power - blue) and 4 (Power signal - white). This leaves the ground (pin 1) and canbus wires (pins 9 &10) connected. I should have actually measures the resistance of the canbus pins on the TCU. On doing this, so far I've only seen 2 DTCs return (EV/HEV codes, presumably due to not being able to communicate with the TCU). I'll need to try it for a while to see if any others come back.

And I also wish I noticed how easy it is to remove the TCU previously. It was a pain originally getting a hand up in there and getting the connector out. The TCU just had to screws on the front of its bracket and was trivial to remove, making it much easier getting at the wiring.

No bus errors so far

I just disconnected both TCU connectors on my 2011, while the 12v battery was disconnected, so as not to freak out anything on the bus. I went for a test drive and have not yet noticed anything out of the ordinary. LeafSpy is showing four pretty reasonable codes:
P31C2 00C0 EV/HEV TCU EVC-273
U1000 00 CO EV/HEV CAN Comm Circuit
>U1266 0209 MULTI AV TCU Conn AV-92

Based on your results, it seems like the other systems want to see something on that empty CAN. Why not run OVMS from pins 1, 2, 9 & 10 instead of on the OBD? Wrong bus?

Just disconnect the TCU

I think disconnecting the TCU should be as effective as cutting the power wires. You might receive one less DTC code. The only codes related to TCU disconnection should be the four listed above; BRAKE and BCM codes are unrelated to this but may be related to the 12v battery.

The TCU connector only contains the EV canbus; OVMS requires both the EV and CAR canbus, so plugging or tapping into the OBD port is the best option. More info here: https://mynissanleaf.com/viewtopic.php?f=27&t=25949&start=20

KimberlyNewman's picture
Oh, I honestly don't know

Oh, I honestly don't know what could be the reason for this occurring! Don't you think it would be better if you find a specialist who can run a car diagnostic check for you? At least, that's what I did when the temperature control unit wasn't working properly. That will save you a lot of time, plus they're professional, and they know what they're doing! Anyways, I wanted to check with you whether you know any companies that offer scrapping services? I'm thinking of scrapping my van, and I don't know any! Your help will be very much appreciated! Thanks!

So what about https://docs

So what about https://docs.openvehicles.com/en/latest/components/vehicle_nissanleaf/docs/index.html#models-aze0 are we saying is wrong specifically?  Should the documentation be updated based on learnings here?

Stanton's picture
The documentation is

The documentation is basically correct: simply unplug the TCU (2 connectors plus the antenna) and the OVMS module should work. The additional 2011-2013 mod for remote climate control (pull pin 11 high) is also correct, but doing so will drain the 12v battery fairly quickly...so I rigged a "dummy" receptable to connect pin 11 to pin 1 (12v) only when I want to pre-heat outside of a charging event (which isn't very often).

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