R34 GT with Neo Engine - No Speedo

[6BANGER]

Before we get into it, I have been searching the entire Internet and the R34 manual for the past week without much luck.

Now, here is the problem.

I have a R34 GT which came with a RB26 engine setup for RWD. It also came with the RB26 loom and ECU. This  Everything worked well along with the R33 gearbox. 

After building the RB26, I decided to swap the motor with a RB25det NEO engine, gearbox, loom and ECU. Yes, this is when the speedo stopped working.

I have traced the issue down to the TCS/ABS ecu as the GT (NA) ECU does not have TCS but the GTT ECU is now looking for a signal from the TCS.

 

Here is what I have tried so far...

1. Run a wire from the speed sensor in the gearbox to the cluster and ECU

2. tested for continuity between ABS computer and cluster (speed signal wire) - all ok

3. tried a second hand cluster that was working at the time

4. used self diagnostics and got the following codes  (26 - 44 - 46 ) 2 of them related to TCS/ABS

 

The golden question is How can I get my speedo to work again???

Edited May 27, 2018 by 6BANGER

[GTSBoy]

9 hours ago, 6BANGER said:

I have traced the issue down to the TCS/ABS ecu as the GT (NA) ECU does not have TCS but the GTT ECU is now looking for a signal from the TCS.

 

 

This is not true.  The speed signal starts out at the speed sensor as a +/-1 volt sawtooth (roughly AC) signal generated by the rotation of the sensor.  The 2 wires associated with this go to the cluster, where the speedo reads it and displays it.  The speedo head also converts the signal to a 0-5v square wave pulse that it puts onto the bus.  The ECU looks for that signal.  So do the other CUs that use it.  The fact that an ABS or other CU is not present should not cause it to not work.

The ECU will certainly be chucking a code if the other CUs it expects to hear from are not present.  You need to Nistune the ECU to be able to fix that.

If I had to guess, I would say that your loom transplant has done something undesirable.

[6BANGER]

I will try to test it with a Nistune ECU as soon as I get a hold of one. In the mean time, I was hoping its a matter of running a direct feed someone to by pass this issue

[GTSBoy]

I described the "direct feed" above.  That's the way it works. Wire it up like that and it will either work, or something is broken.