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IAT Wiring on an RB25DET S2


Jarsky

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Hi all,

 

I'm currently installing my Link G4X (NGTRX) in my 1997 Nissan Skyline R33 GTS-T Series II (RB25DET S2). 

The instructions advise that I can use An Temp 2 which on the GT-R is mapped to Pin 36 on the ECU. 

I installed my IAT but the ECU was throwing error fault codes for the IAT. 

So i re-ran new wiring using Milspec AWG20 and DTM deutsch connectors (thinking maybe my wiring was bad, I was using some cheap extremely thin wire). Still the same fault. On re-checking my ECU wiring I realised I put the wire in Pin 37. The reason, is that there is a grey wire already in Pin 36, that runs up into the loom? 

On reading the Pinout diagram again, I see almost none of the colors in my wiring loom match.

e.g Pin 32 should be Orange/Black but its Red/White, Pin 38 should be White, but its Red/Blue. The sensor ground on Pin 30 should be Black but its Blue/Purple....

The ECU plug still had the factory seal tape on it and undoing the bolts the ECU has definately never been out. So im at a loss as to why there is a grey wire in Pin 36? In all the years i've owned this Skyline ive never seen any additional sensors on it (the only mods it had before I got it was a Tial BOV, 3.5" Catback exhaust and Podfilter intake). All the factory shielding and clips are still on the loom so i dont believe anyone has added that pin. 

Should I just pull the existing Pin 36 out? I'm not so concerned about the color mismatch but i'm concerned why there is an existing factory wire in Pin 36 and what its function therefor is if there are differences between the S1 & S2 RB25DET ECU Pinouts...

 

Screenshot 2022-10-20 144031.png

20221020_180345.jpg

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In our library we do have one wiring diagram that is a bit different to all the others we have, it appears to have been translated from japanese, but in this diagram it looks like pin 36 is used as a signal from the FICD relay.  I dont know what the device is connected to pin 54 and 46 in this diagram (maybe climate control unit?), but usually 54 is an idle switch and 46 is the AC request.  From the look of that circuit I would say it is that device that is controlling the FICD relay and not pin 36.

Our ecu doesnt use the FICD so you can remove that wire and use pin 36 for temp.

ACZXS5y.png

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