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Mytqik's TB45 to TD42 wiring guide

48022 Views 104 Replies 21 Participants Last post by  Jjjag2099
I am I the process of converting my GU Ti TB45 auto over to a TD42 auto. There is a link in my signature to my build thread for more information on the mechanical side of things.

Everything below is to suit a 1994 black top GQ TD42 into a 1998 GU Ti TB45. Please double check everything before following my lead :)

As I do the wiring I thought I would document it, save anyone else the hours that I have trawled over GQ & GU wiring diagrams.

The heavy Black/red (50mm2) main power cable can be re-used. I re-lugged it to suit my new battery terminals better.
The White/red (6mm2) wire will need to have the blade plug cut off the end and a ring crimped on.

The alternator and P/S pump are on different sides from the TB to the TD, therefore the TB wiring will need to be extended to suit.
I used my old 50mm2 winch power cable in place of the *********** cable that runs from the ALT to the fuse box.
The black wire needs to be extended with a ring crimped on the end.
I found that the plug for the yellow/red & yellow/black is actually the same plug/pin outs as the TD42 alt, so I just extended these 2 wires and re-used the TB45 plug.
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Can the TB45e TCU be used without the ECU? What is it relying on?
The wiring diagram shows 4 wires going between the TCU and ECU. You would need to work out what they are etc.
I would suggest not using the TB45 TCU unless the ECU is there and communicating to it.
If you want to use a Nissan TCU without a ECU present, then try a TCU from an automatic carby 4.2 GQ.
Throttle Position Sensor:
Since both my GU and my donor GQ where auto's I was lucky enough to have the TPS on the fuel pump.
Matt at UFI did a great job of pulling the TPS off my 10mm pump and grafting it onto my DC3 11mm pump.

There are 2x 3 pin plugs on the TB45, one for the throttle position sensor and one for throttle position sensor and one for throttle position switch. On the TD42 this is combined into 1x 6pin plug.
(I had to find a French copy of the GQ manual before I could find a wiring diagram for a TD42 auto!!)

Throttle Position Switch:
Green/Orange.....12V power.......Green/Red
White/Green........Full Throttle....Green/Black
Black..................Idle................Light Green

Throttle Position Sensor
Orange...............12V power.......Yellow
I made typo in the Throttle Position Switch:
Red/blue.............Idle.................Light Green

Here is a photo:
Thanks for all the info in here Mytquik. Wish I found your TPS wiring info in post 14 before I wasted a lot of time looking for that info. I posted a few of my same findings in here (which also has some good info on TPS part numbers etc.);

I hope i'm not seen as too anal by correcting a minor issue in the quoted info above.
It isn't 12v positive or negative that goes into the TPS. It's 5v, and both + and - is coming from the TCU just for the purpose of TPS. The factory wiring diagrams show what pins it comes from, so if you are wiring a TPS to feed into your TCU, then it should be obvious that you feed it from the TCU and not an external 12v + and - source.
Thanks Snatchy.

I have not seen the diagrams yet, just starting to research this project, I am assuming from threads I've read on here there is some kind of datalink between the two control units.

I am looking at putting an auto into a GU factory TD42ti. Was hoping to buy all the bits from one vehicle and I have found a couple of wrecked TB45 autos with all the extra bits but by the sounds of it I can't use the TB45 TCU.
Good luck with the project. I'm half way through the same thing but on a GQ TD42.
Yeah the TB42 carby TCU would suit you I gather. There was one on gumtree for $75. You will find one cheap if you dig around.
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