Jump to content
SAU Community

Recommended Posts

Howdy fellas. I have an issue:

TL;DR - 34 GT - Turbo & manual converted (Speedo was working) - Installed 34 GTT motor and loom - Replace ECU & Tuned - Now no speedo. Checked wires from sender & reversed. Checked fuses in drivers footwell (trip metre fuse in drivers footwell). Only other change was the *Anti Skid Control* box has been removed.

Send help please: Unsure of where to go next.

Long story - 
Bought car, already manual converted. Replaced motor with GTT motor and motor loom (loom all the way to ECU plug). The plugs didn’t match the Anti skid control so I’ve ordered one from a GTT but I don’t think that will fix it. I investigated the speed sender and signal seems good. Unsure of where to go next.

Update** Now suspect maybe gearbox loom or earth isn’t quite right? Maybe it came look/dislodged in removing the motor?

I have trawled the hell out of Skyline Owners and SAU before someone links an article there.

Link to comment
https://www.sau.com.au/forums/topic/475507-r34-speedo-issue-send-help/
Share on other sites

I have to plead a little ignorance of what should have been on your car in its original state.....but it is my gut feeling that the NA auto R34s had the speed sender on the diff nose, not the gearbox.  I might be wrong, but it is something to consider.

The RB25DET's manual gearbox speedo sender creates a +/- 1V signal (essentially an AC voltage), the frequency of which varies with speed.  The speedo head reads this and converts it to the 0-5V square wave PWM signal that gets put out onto the speed signal bus (which goes to the ECU/TCU, the ABS/TCS & HICAS CU).  All of those CUs are only receivers on the speed signal bus.  None of them create the speed signal.  Any one of them can be missing completely and the speed signal should still be available.  So long as the speedo head is still doing its job.

The only wires you have to worry about are the 2 wires that run from the speed sender to the speedo.  There is no power (car battery 12V, no earth) involved.  Just the connection between sender and speedo.  of course, the speedo is separately powered off the dash.

It is just possible that the diff mounted speed senders create a different type/quality signal from the gearbox ones and that might explain the speedo head's inability to read it.

There are other alternatives.  The speed signal might be good, the speedo might be good (in terms of receiving the original speed signal and transmitting the square wave version out on the bus.....but the head might have simply died as a coincidence.  Unlikely -- coincidences are to be suspected.  But possible.  A worthwhile test will be to put a scan tool onto the car and take it for a drive.  See if the speed signal is visible from the ECU.

As stated in original, speed was working with manual conversion before hand. Only since removing old motor and putting in GTT motor has issue occurred.
Aftermarket ECU is installed now as well so diags won't help.

Edited by R34GTTBoi
  • 3 months later...
  • 1 year later...
On 13/03/2019 at 8:34 AM, R34GTTBoi said:

Ended up being the wire to the dash - ran one manually and we were good to go.

Im having same issue after replacing motor. No rpm, speedo and faulty temp. Where did you run a wire to and from? Think this might solve one of my issues. Cheers

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • It would be well worth deciding where you want to go and what you care about. Reliability of everything in a 34 drops MASSIVELY above the 300kw mark. Keeping everything going great at beyond that value will cost ten times the $. Clutches become shit, gearboxes (and engines/bottom ends) become consumable, traction becomes crap. The good news is looking legalish/actually being legal is slighly under the 300kw mark. I would make the assumption you want to ditch the stock plenum too and want to go a front facing unit of some description due to the cross flow. Do the bends on a return flow hurt? Not really. A couple of bends do make a difference but not nearly as much in a forced induction situation. Add 1psi of boost to overcome it. Nobody has ever gone and done a track session monitoring IAT then done a different session on a different intercooler and monitored IAT to see the difference here. All of the benefits here are likely in the "My engine is a forged consumable that I drive once a year because it needs a rebuild every year which takes 9 months of the year to complete" territory. It would be well worth deciding where you want to go and what you care about with this car.
    • By "reverse flow", do you mean "return flow"? Being the IC having a return pipe back behind the bumper reo, or similar? If so... I am currently making ~250 rwkW on a Neo at ~17-18 psi. With a return flow. There's nothing to indicate that it is costing me a lot of power at this level, and I would be surprised if I could not push it harder. True, I have not measured pressure drop across it or IAT changes, but the car does not seem upset about it in any way. I won't be bothering to look into it unless it starts giving trouble or doesn't respond to boost increases when I next put it on the dyno. FWIW, it was tuned with the boost controller off, so achieving ~15-16 psi on the wastegate spring alone, and it is noticeably quicker with the boost controller on and yielding a couple of extra pounds. Hence why I think it is doing OK. So, no, I would not arbitrarily say that return flows are restrictive. Yes, they are certainly restrictive if you're aiming for higher power levels. But I also think that the happy place for a street car is <300 rwkW anyway, so I'm not going to be aiming for power levels that would require me to change the inlet pipework. My car looks very stock, even though everything is different. The turbo and inlet pipes all look stock and run in the stock locations, The airbox looks stock (apart from the inlet being opened up). The turbo looks stock, because it's in the stock location, is the stock housings and can't really be seen anyway. It makes enough power to be good to drive, but won't raise eyebrows if I ever f**k up enough for the cops to lift the bonnet.
    • There is a guy who said he can weld me piping without having to cut chassis, maybe I do that ? Or do I just go reverse flow but isn’t reverse flow very limited once again? 
    • I haven’t yet cut the chassis, maybe I switch to a reverse flow. I’ve got the Intercooler mounted as I already had it but not cut yet. Might have to speak to an engineer 
    • Yes that’s another issue, I always have a front mount, plus will be turbo plus intake will big hasstle. I’ve been told if it looks stock they’re fine with it by a couple others who have done it ahahaha.    I know @Kinkstaah said the stock gtt airbox is limiting but I might just have to do that to avoid a defect so it atleast looks legit. Or an enclosed pod so it’s hidden away and feed air from the snorkel and below Intercooler holes like kinstaah mentioned. Hmm what to do 
×
×
  • Create New...