Speedo Out - Apexi Rsm Dosn't Help - Please Help!

[colossus]

Hey guys I have an R34 GTT auto - it was not showing gears on the dash so I bought a second hand dash cluster with a non working speedo (only goes up to 6km/h). My plan was to swap my good speedo into this second hand dash which I did. However this did not solve the speedo problem (it appears speed info is stored in a chip in the dash that cannot be changed out).

So as a last resort I bought an Apexi RSM - hooked it up with my old dash connected and it worked perfect (so its not an RSM wiring problem). Put the non working speedo dash in and now the Apexi only also goes up to 6km/h (so it mimicks what the dash is saying).

So what I dont understand is that the APexi RSM is wired straight into the ECU - why the hell does it need the dash connected and operitng to make the RSM work???

Any help appreciated

PS - (As a plus I can now change out a dash console in 7 minutes as I've done it elevtny billion times in the last day! )

[666DAN]

OK I'd swap the Auto display section from the dodgy 7kmh dash into your old one, it sits on a kind of sub-board that solders in (providing it's series 1) obviously it's nothing major as the gear-shit control is routed through the dash to operate properly (god knows why)

This should then give you your original Kms (as it's the originaly dash) and working gear shift indicator

The dash seems to do a lot more than previous models, I'm pretty sure the speed signal is decoded dash side in the Autos, I saw something similar with a guy that put a GTt dash into a 25GT and it didn't want to communicate and wouldn't display rpm correctly.

[colossus]

Only problem with that is I dont have my original dash anymore - gave to a mate already who didnt care about gear indicators (I could probably get it back though).

I did some more research and it seems speed signal is sent by gearbox to dash with drives speedo and then sends info to ECU. So by splicing RSM into ECU it is just reading what the speedo is reading...

So if I took speed signal from somewhere else like ABS unit or straight off gearbox (if I can find the speed wire) I wonder if that would work.....

[666DAN]

Try wiring the RSM to pin 58 instead of 29....Auto's have 2 speed sensor outputs, the second may work fine as it's what the gearbox uses...hopefully the output signal is the correct format.

R34_ECU_pins.doc

[colossus]

Try wiring the RSM to pin 58 instead of 29....Auto's have 2 speed sensor outputs, the second may work fine as it's what the gearbox uses...hopefully the output signal is the correct format.

R34_ECU_pins.doc

Ok thanks - tried it and now I am getting a speed reading of 1200km/h (when doing 20). So changed the Vehicle Speed Pulse Signal from 2 in the RSM (this is the Nissan setting) to 80P. This "felt" kind of right from seat of the pants but wasnt sure, so went over to another mates house and convinved him to let me test with his cluster.

So now with a good R34 cluster set up and RSM connceted to pin 58 - when doing a speedo indicated 40km/h the RSM is showing 32km/h, at 60km/h speedo, RSM is showing 52km/h at 80km/h RSM showing as 72km/h. So not too far out - I wonder why there is this difference? IS this due to speedos purposly having a 10% error from factory so you dont get booked speeding, or something different...

[colossus]

OK figured it out. If anyone in the future has a broken speedo and an Apexi RSM do this:

Use pin 58 instead of 29 as Dan said for the speed wire (purple) which takes the speed output off the gearbox instead of the dash. Then in the RSM set speed pulse to 80P (instead of 2P) then under "adjust menu" adjust to 117% (instead of 100%). This will give you the true speed reading.

Did this calibration at all speeds up to 120km/h and seems to work perfect. Cheers.

[colossus]

Ok now I have another problem....

Took car for a 30 minute spin everything was fine but as I turned right into a parking spot the car stalled (less than 10km/h - its an auto BTW).

So took it round the block, slowed down and turned into a parking spot and again it stalled.

Took it out again did like another 10 slow turns and it wouldnt do it. But I know it will happen again...

With car running wiggled all the wires I cut in the ECU and it wouldnt stall out.

Any ideas?

[merlin6014]

Maybe ECU just needs some time to "learn" the new dash (i assume you had the battery unplugged and hence reset ecu during install).