[Ovmsdev] Nissan Leaf remote climate control update

[Tom Parker]

I spent some time with a friend's Gen 2 Nissan Leaf and got to the 
bottom of why the remote climate control works on some cars and not others.

It turns out that if you have CARWINGS (now called NissanConnect) 
hardware in your car, the Nissan TCU module sends "Status" (0x4e) and 
"Idle" (0x86) messages on CAN frame 0x56e. These override the "CC On" 
(0x4e) message (0x4e) I'm sending with the OVMS and shut the car down.

If you have a TCU module, the solution is to unplug it. I haven't 
noticed any problems doing this, I unplugged my TCU (on my Gen 1 I had 
to do this to access the hardware wakeup wiring) about 6 months ago. My 
friend has been going a few days in his Gen 2 with no problems.

Unplugging isn't terribly difficult on a right hand drive car, you have 
to remove a panel above the driver's feet and then contort yourself in 
to press the release latch and pull out the big plug. I didn't bother 
unplugging the antenna and USB connection to the AV unit, and I coudln't 
work out how to release the entire module without taking more of the car 
apart.

I do notice a check engine light when I use the remote climate control 
but it goes away after your turn the car off an on again and doesn't 
affect the performance of the car. I'm guessing something notices that 
the OVMS isn't faithfully emulating all the TCU funcitons. If anyone has 
a working NissanConnect and could capture the can bus for an entire 
remote climate control session, from startup to shutdown, maybe I can 
get rid of this problem.

I've sent a pull request that decodes the HVAC status, allowing the 
android app to show whether it's on or off.

Is the iOS app still maintained? I'd like to remove the Homelink hack 
(where remote climate control is available on homelink 1 (on) and 
homelink 2 (off)) when it has the new HVAC command.