Best way to disconnect TCU

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EmmaK1

Member
Joined
Oct 30, 2022
Messages
14
Hello,

I live in the NW UK and have a Japan built 2011 ZEO with a Muxsan 11kW range extender. (68,000miles and just dropped to 9 bars on battery indicator.)

Like many owners I have been having problems with the car killing the 12v battery in short time. I fitted a new 12 battery when i bought the car but it has killed 4 batteries in 5 years, the last one survived 20 months with monthly conditioning charges using a pulse charger.

After much reading on this forum, thank you chaps, and other forums and three converstions with Emile at Muxsan I have decided to fit a Optima DS46B24R (which I am sure you are aware is sold specifically for the Toyota Prius). The Optima data sheets and reports I have read on other forums are generaly favourable to this. Before doing so I wish to disable or disconnect the TCU. This link to a UK discount vendor https://www.tayna.co.uk/car-batteries/optima/ds46b24r/

I am reasonably computer literate but not an enthusiast and am not interested in updating to OVMS... I just want a reliable car. However there is so much conflicting advice that I am a little confused. I have never had the "nag screen" appear. (Is it something on US spec. cars?) And want the minimum alarms or error codes.


Am I correct in understanding that this can be achieved by cutting the wires to pins 1, 3 and 4 on the TCU white plug?



I understand that unplugging the white plug only can trigger multiple alarms/error codes and some suggest removing only the grey plug or completely removing all three while one person identified white plug pin 1 as both the battery live and the earth (ground) in the same paragraph. :?

Thank you in advance for your advice.

Emma
 
Do not cut any of the wires/pins on the TCU connector. It's not necessary to achieve what you want to do, and it prevents you from ever using those connectors again.
There's nothing wrong with simply disconnecting (all) of the TCU plugs. It won't prevent you from driving the car and any DTC's shouldn't even result in a dash light/error. There's no guarantee this is the source of your "phantom drain", but it is a good place to start.
 
Thank you Stanton.

I will take your advice on board. I am not worried about error codes that can only be read by diagnostic/leafspy. I just don't want alarms/warning lights or anything that is not easily resetable.

KR, Emma

p.s. Cut wires can always be reconnected providing you leave a decent tail... Solder and shrink wrap. :)
 
Nissan has an official TSB on disabling the TCU, as it's a security concern.

Also, because it's a security issue, I'm pretty sure dealers have to disable the TCU upon request for free. It's a so called voluntary recall, if memory serves. Anyways, worth a phone call to a local Nissan dealership to find out.
 
coulomb said:
alozzy said:
Found it...
That one says NOT to disable a 3G TSU.

If there isn't one already, I think there will have to be one saying disable the 3G TSU, but don't disable a 4G TSU.

And maybe in 10 years...

A 2011 Leaf, like the OP has, uses a 2G radio in the TCU, no?
 
So a lot more investigation later...

Our local Nissan dealer knows nothing and have only done recall work on the few Leafs (Leaves?) in the area. They replaced one traction battery under warranty and due to lack of facilities hired a mobile crane to lift the car off the battery! :roll: But they did confirm the car has 2G.

Checking with mobile sevice providers the 2G cover where I live is bad. To quote one provider "Very poor signal outdoors, no signal indoors". This tallies with my experiences of 2G (and 3G) mobile phones when I first moved here. My understanding is that the TCU is (was) trying to connect to Carwings and with no response is staying on when I stop the car so running down the battery. I checked with Muxsan, (who had independently suggested disconnecting the TCU in a previous conversation), had one more re-read of threads on here and the OVMS pages (which is worth doing as it clarified and confirmed my thoughts) and decided to remove the TCU.

This morning (03/11/22) I removed the TCU. You guys with LHD cars have it a lot easier going in through the glove box space! ;) I have listed a few of pointers for those with RHD cars who may decide to follow me:-

1) The black panel over the pedals is retained by two plug clips (turn the cross head insert 90 degrees and pull out) and two steel spring clips. A stong downward tug releases the spring clips. It is not necessary to completely remove the panel as there is enough room to work with it dropped down.

If you look up and right under the dash you can see the black TCU box screwed to a steel bracket. It is almost impossible to release the plugs. Even if you were familier with the release catches it would be extremely difficult if not impossible. There are two socket headed srews but undoing them will not release the TCU as there are two more at the top! There are two black philips headed screws visible behind and above the release levers. These must be removed to release the TCU on its bracket.

2) The bonnet and charge port release is hooked into the dash. After removing the two bolts lift and pull back to disengage. (Mine was stuck (just been there a long time) and initially I had some difficulty getting it to move.)
3) Pull back the door seal just enough to uncover the end of the dash and prise out cover on end of dashboard. It is hinged at the front edge by lugs that engage in slots.
4) The corner of the lower part of the dashboard can be pulled away. I found it easiest to start nearest the steering column and lever with a wooden spatula. The release is horizontaly backward (Not down and back). You can then reach in over the top of the lower dash panel.
5) Two cables are clipped to the left side of the steel TCU mounting bracket. It is almost impossible to lever these clips out so I cut them. (Sawed through very carefully using a serated edge kitchen knife.)
6) Remove the two black philips screws holding the TCU bracket to the vertical support bar then the TCU on its bracket can be moved left and dropped down. It is then easy to unplug the three connectors.

The grey one is made of a brittle plastic and it is easy to break the release tool loop. :oops: It is also deep and needs to be slid out parrallel to sides of its socket. There are no exposed pins so I just tucked the plugs up over the edge of the top half of the dashboard before reassembly.

I reconnected the battery and everything seems to work normaly with no alarm or warning light. I have not yet checked for error codes. I then reassembled the dashboard. The bottom right corner of the lower dash does not line up with anything and looks "wrong" to me but is covered by the end panel which fitted back perfectly.

When I disconnected the 12v battery a relay clicked so something was live, but I did have the drivers door open so it could have been something to do with the courtesy light. What sounded as though it was the same relay also clicked when I reconnected the battery.

I have fitted an Optima Yellow Top YTS 2.7 R Battery which is a straight replacement. Unfortunately it is a 38Ah but the next size, up 48Ah, is a bit too big to fit in a ZEO battery tray without modifications. This deep cycle + starting AGM battery is claimed to hold a steady voltage deeper into the discharge cycle, be much more tolerant of long periods of lower charge levels and sustain many more discharge/charge cycles than a "starting" wet battery. It is also claimed to be less affected by vibration which is probably a good thing where I live. We shall see. :? Where I live the temperature rarely drops below freezing so hopefully with the vampire drain gone (fingers crossed) and regular maintenance charges, this battery will last a long time.

I am going to fit a (fused) pigtail through to the charging port but I have to work in the street and it has started raining (again :roll: ) so will leave this until the next dry day.

I hope this may be useful and will continue to update this thread with my experience of these mods, good or bad. :geek:
 
Unfortunately it is a 38Ah but the next size, up 48Ah, is a bit too big to fit in a ZEO battery tray without modifications.

Don't worry about that. You will have more available capacity than you had with the OEM battery, because the new one is deep cycle. When you connect the pigtail, connect the Negative lead to something other then the Negative terminal on the battery. There is a current sensor there. There should be a screw available on top of the motor/inverter assembly.

Alternatively, if you want to be brave, you can temporarily (for the Winter months) boost the 12 volt charging by removing that current sensor, which will cause the 12 volt charging system to stay active, providing a constant ~14.4 volts. The risk is that this will "cook" the new 12 volt battery, although that outcome hasn't, AFAIK, been reported. I wouldn't do it, but others have.
 
EmmaK1 said:
So a lot more investigation later...

Our local Nissan dealer knows nothing and have only done recall work on the few Leafs (Leaves?) in the area. They replaced one traction battery under warranty and due to lack of facilities hired a mobile crane to lift the car off the battery! :roll: But they did confirm the car has 2G.

Checking with mobile sevice providers the 2G cover where I live is bad. To quote one provider "Very poor signal outdoors, no signal indoors". This tallies with my experiences of 2G (and 3G) mobile phones when I first moved here. My understanding is that the TCU is (was) trying to connect to Carwings and with no response is staying on when I stop the car so running down the battery. I checked with Muxsan, (who had independently suggested disconnecting the TCU in a previous conversation), had one more re-read of threads on here and the OVMS pages (which is worth doing as it clarified and confirmed my thoughts) and decided to remove the TCU.

This morning (03/11/22) I removed the TCU. You guys with LHD cars have it a lot easier going in through the glove box space! ;) I have listed a few of pointers for those with RHD cars who may decide to follow me:-

1) The black panel over the pedals is retained by two plug clips (turn the cross head insert 90 degrees and pull out) and two steel spring clips. A stong downward tug releases the spring clips. It is not necessary to completely remove the panel as there is enough room to work with it dropped down.

If you look up and right under the dash you can see the black TCU box screwed to a steel bracket. It is almost impossible to release the plugs. Even if you were familier with the release catches it would be extremely difficult if not impossible. There are two socket headed srews but undoing them will not release the TCU as there are two more at the top! There are two black philips headed screws visible behind and above the release levers. These must be removed to release the TCU on its bracket.

2) The bonnet and charge port release is hooked into the dash. After removing the two bolts lift and pull back to disengage. (Mine was stuck (just been there a long time) and initially I had some difficulty getting it to move.)
3) Pull back the door seal just enough to uncover the end of the dash and prise out cover on end of dashboard. It is hinged at the front edge by lugs that engage in slots.
4) The corner of the lower part of the dashboard can be pulled away. I found it easiest to start nearest the steering column and lever with a wooden spatula. The release is horizontaly backward (Not down and back). You can then reach in over the top of the lower dash panel.
5) Two cables are clipped to the left side of the steel TCU mounting bracket. It is almost impossible to lever these clips out so I cut them. (Sawed through very carefully using a serated edge kitchen knife.)
6) Remove the two black philips screws holding the TCU bracket to the vertical support bar then the TCU on its bracket can be moved left and dropped down. It is then easy to unplug the three connectors.

The grey one is made of a brittle plastic and it is easy to break the release tool loop. :oops: It is also deep and needs to be slid out parrallel to sides of its socket. There are no exposed pins so I just tucked the plugs up over the edge of the top half of the dashboard before reassembly.

I reconnected the battery and everything seems to work normaly with no alarm or warning light. I have not yet checked for error codes. I then reassembled the dashboard. The bottom right corner of the lower dash does not line up with anything and looks "wrong" to me but is covered by the end panel which fitted back perfectly.

When I disconnected the 12v battery a relay clicked so something was live, but I did have the drivers door open so it could have been something to do with the courtesy light. What sounded as though it was the same relay also clicked when I reconnected the battery.

I have fitted an Optima Yellow Top YTS 2.7 R Battery which is a straight replacement. Unfortunately it is a 38Ah but the next size, up 48Ah, is a bit too big to fit in a ZEO battery tray without modifications. This deep cycle + starting AGM battery is claimed to hold a steady voltage deeper into the discharge cycle, be much more tolerant of long periods of lower charge levels and sustain many more discharge/charge cycles than a "starting" wet battery. It is also claimed to be less affected by vibration which is probably a good thing where I live. We shall see. :? Where I live the temperature rarely drops below freezing so hopefully with the vampire drain gone (fingers crossed) and regular maintenance charges, this battery will last a long time.

I am going to fit a (fused) pigtail through to the charging port but I have to work in the street and it has started raining (again :roll: ) so will leave this until the next dry day.

I hope this may be useful and will continue to update this thread with my experience of these mods, good or bad. :geek:

Before all this effort, did you ever attempt to check the battery current drain after all ECUs enter their sleep mode,
i.e. about 3-4 minutes? The typical battery sleep mode current should be less than 100 ma (.10 amps),
it's about 60 ma on each of my two Leafs. It can be easily checked with a clamp-on ammeter .
 
alozzy said:
Seems like an awful lot of work when you could have gotten the Nissan dealership to deactivate the 2G TCU for free.
If that really was his problem (TCU phantom load), then simply "deactivating" it may not have been enough. Removing/disconnecting it is the only way to be sure.
 
Thank you for all the input guys.

Unfortunately there has been very little support for older electric cars in the UK, even less in the backwater where I live. I am a 66 y.o. woman. I do not undertake these tasks for pleasure. I do it because I believe in electric cars, very much enjoy using mine and want it to be reliable.

The NHTSA notice is for the USA. I live in England, part of the United Kingdom. There has been no recall I am aware of for this (I have checked online) as 2G is still active here. (It may be discontinued in 2025.) When I purchased the car I was unable to access Carwings. The dealer was no help so I have never had access. Similarly they have not told me Carwings was no longer operational (at the time I never thought to ask just accepting what I have read on the forums). After previous experience with them I would not trust them with any work. Certainly not if I want the car back the same day and charged!

I believe my problems were caused partly by Carwings being deactivated but mainly due to a very poor 2G mobile signal. With my 2G phone I had to climb onto the roof to get a useable signal. Completely disconnecting the TCU guarantees that it will never again be a drain.

12v battery life has been 12 to 20 months before there were problems, which seems to be common on many makes of electric car. I did not think to use a clamp meter sooner as I mistakenly believed from reading on this and other forums that all my problems with the lead acid battery were due to the vagaries of the charging system causing sulphation by the low float charge. It was only after the car flattened a new but cheap (Mr. Snappy 45Ah) battery in 36 hours that I resumed in earnest my search of the online forums. I will buy or borrow a clamp meter presently and check what is going on. Rather annoyingly the morning I removed the TCU the Mr. Snappy battery was still at 12.2 volts after 48 hours. I am keeping a close watch on the Optima 38Ah battery... And trusting that it lives up to it's makers claims. If it does then I have saved £50 on the cost of the 48Ah battery. If it fails I shall go away and mutter rude things in a quiet place! :cry:

Overnight the temperature dropped from 14 to 0 centigrade but the voltage remained at 12.62 (ignition off) and it was still there at lunch time today after driving 45 miles.

Regards to all, Emma
 
Photos of the TCU location on a RHD car here:- https://mynissanleaf.com/viewtopic.php?t=18598
 
Sorry for the US bias of my reply, what a bummer that there's no recall in the UK and no worthwhile dealer support.

I hope you are able to find out what's causing the phantom drain on the 12V system. Once you have an ammeter, if you find there's a constant drain on the 12V battery then try unplugging one fuse at a time, then plug that fuse in and move onto the next one until the load on the battery drops. That way, you can at least figure out where to look for a short or a mystery load.
 
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