R34 - Switching cluster from non turbo auto --> turbo manual after diff change

[tommytomatoes]

Hi guys,

R34 sedan I have was originally a non turbo automatic. Speedo is read in analog from the sensor on the diff pinion. Put in a nismo manual cluster and confirmed speedo did not read, switched back to auto cluster for and was happy with it.

I then grenaded the diff and could only find a short nose replacement. So I am now at the point of wiring in the transmission digital sensor to the cluster, but I cannot find any wiring schematics in the R34 service manual that are useful. 

Questions: 

1) Do we have wiring schematics available for R34's? 

2) Do the 2x speedo wires go straight to the cluster from the trans sensor or via an ECU to calibrate and read correctly?

3) Now I have a hard ABS light on due to analog speed sensor not being connected to the diff. What are my options regarding ABS. Does everyone pull a fuse/relay to eliminate it or can you incorporate/convert it?

Any help/insight would be greatly appreciated. I've searched the forum for an hour or so and cannot see if anyone this specific issue, if there is a thread that solves my issue sorry in advance!

[GTSBoy]

Gearbox sender is 2 wires to cluster. It is a +/- 1V AC sawtooth type signal. Should not be greatly different to that from the diff, except for pulse count per speed.

The ECU has nothing to do with it. The ECU and every other CU is a client of the speed signal generated in the cluster by the speedo head. That is a 0-5V PWM signal.

All this is in the R34 manual.

[tommytomatoes]

Thanks! I guess I’ll take a closer look at that section. 

[tommytomatoes]

1 hour ago, GTSBoy said:

Gearbox sender is 2 wires to cluster. It is a +/- 1V AC sawtooth type signal. Should not be greatly different to that from the diff, except for pulse count per speed.

The ECU has nothing to do with it. The ECU and every other CU is a client of the speed signal generated in the cluster by the speedo head. That is a 0-5V PWM signal.

All this is in the R34 manual.

So there is one vehicle speed sensor input wire [#19]

The 2 vss output wires are 2 pulse [#30] and 8 pulse. [#31]

Im guessing 2P is for manual transmission sensor and 8P is for auto final drive speed signal. It would be safe to assume whichever one I have, I should wire in the opposite for ground. I need to put a fuse on the ground side too by the looks of it.

[GTSBoy]

No. I would presume not. I cannot see why there would be 2 different outputs based on what the input type was.

 

I would presume that the 2P output is used by some clients in the car, and the 8P would be used by other clients (think of the various CUs in the car, ECU, TCU, ABS, HICAS that want to know a speed signal).

The only input is pin 19 and the input needs to come to pin 19 from whichever speed sender is in the car.

 

Look at the whole wiring diagram to see where the dash's pins 30 & 31 go. But the answer won't be there. That's just for interest. Just wire up the gearbox speed sender to the dash input 19 in the same was as it was from the diff. There is no power involved. The +/-1V signal is GENERATED by the inductive sensor.

[tommytomatoes]

I tried straight wiring to #19 and #30. No luck, tomorrow I will try reversing the polarity (no idea if it matters or not) and then using #31 instead of #30 as a ground. See if that fixes it.

[GTSBoy]

There is no ground. Which part of +/- 1V are you having trouble with? The speed sensor generates an AC signal. Both wires are positive and both wires are negative, just not at the same time.

[tommytomatoes]

Sorry +/-1V meant nothing to me, if you said the polarity didn’t matter I would understand.
Time to switch out #30 for #31, thank you gts boy, I do appreciate the help.

[GTSBoy]

No. Don't mess with #30 and #31. They are outputs. They go to CUs that want to see a speed signal. That signal is generated in the dash. The input from the sensor has to go onto #19 (and because it is an AC signal, there really should be a 2nd wire for that connection - you shouldn't be able to use body earth).

[tommytomatoes]

So what should be done with the 2nd wire from the speed sensor harness, ground it?

[GTSBoy]

6 hours ago, tommytomatoes said:

So what should be done with the 2nd wire from the speed sensor harness, ground it?

 

22 hours ago, GTSBoy said:

you shouldn't be able to use body earth

 

Edited September 7, 2020 by GTSBoy

[tommytomatoes]

This is why I need a wiring schematic, takes out all the guess work. If it doesn't go to a body ground I have no indication of where it does go in the fsm.

Are you indicating it goes to a ground thats not a body ground? Sorry I seem to be misinterpreting you quite a bit here.

[GTSBoy]

No. No ground at all. It cannot connect to a ground, because ground implies zero volts. The signal we are talking about should be a +/- 1V AC signal, which cannot be tied to ground. It need 2 wires from the sensor to the dash.

[GTSBoy]

Hmm. Maybe I correct myself. Seems the service manual shows the speed sensor is grounded on one side.

The manual also has ALL the information you need to fault find this.

Wire it up like this.

 

And use this sort of thing to help you diagnose.

Edited September 8, 2020 by GTSBoy

[tommytomatoes]

Speedo is now operational. Correct wiring is #19 input and ground out the other wire. I put the ground on the crash bar vertical support to the right of the stereo.

Appreciate the help gtsboy! 

[djvoodoo]

Hi guys.

Still trying to find some info. Having replaced my Getrag 3.54 diff ration to 4.11's, my 34R speedo is out. Am planning to use the Jaycar Speedo corrector kit.

https://www.jaycar.com.au/speedo-corrector-module-for-cars/p/AA0376?pos=1&queryId=88be0ef7c2dc84f96cf96bd17b61361f&sort=relevance&searchText=speedo

 

Whilst i understand the speed "input" is pin 19, I need to clarify what pin "30" and "31", that being the speedo output, does to the cluster.

Jaycar's instructions are:

 

But the 34 cluster has both 2 pulse and 8 pulse output. 

Ay ideas?

[GTSBoy]

You don't need to worry about the cluster's output. If you get the input right, the cluster's output will be right.

The way the Nissan speed sensors and speed signals work is:

1. The speedo sensor in the gearbox/transfercase/diffsnout/wherever generates an alternating current (more or less sawtooth) voltage waveform that varies frequency with vehicle speed. (It also changes voltage, getting larger as it turns faster - but that doesn't matter).
2. The speedo head reads that sawtooth waveform and uses it to drive the speedo needle position.
3. The speedo head also outputs a 0-5v squarewave PWM signal that is the VSS (Vehicle speed signal) to the ECU and any other CU on the car that wants to know vehicle speed.

Traditionally, on older cars, there was only the one VSS. But if the 34GTR puts out 2 such, who am I to argue? Anyway, as you can imagine, if you get the input signal right, the cluster will take care of the rest. All you need to do is use the Jaycar module to either speed up or slow down the frequency, as required.

[djvoodoo]

35 minutes ago, GTSBoy said:

You don't need to worry about the cluster's output. If you get the input right, the cluster's output will be right.

The way the Nissan speed sensors and speed signals work is:

1. The speedo sensor in the gearbox/transfercase/diffsnout/wherever generates an alternating current (more or less sawtooth) voltage waveform that varies frequency with vehicle speed. (It also changes voltage, getting larger as it turns faster - but that doesn't matter).
2. The speedo head reads that sawtooth waveform and uses it to drive the speedo needle position.
3. The speedo head also outputs a 0-5v squarewave PWM signal that is the VSS (Vehicle speed signal) to the ECU and any other CU on the car that wants to know vehicle speed.

Traditionally, on older cars, there was only the one VSS. But if the 34GTR puts out 2 such, who am I to argue? Anyway, as you can imagine, if you get the input signal right, the cluster will take care of the rest. All you need to do is use the Jaycar module to either speed up or slow down the frequency, as required.

Thanks @GTSBoy - So pretty much i dont need to wire in the "Speedo Out" wire on the Jaycar unit.

I.E :

1. Power

2. Ground

3. Pin 19 on 34 cluster to speed input wire on Jaycar unit

4. Leave Speed out wire disconnected. Or ground?

[GTSBoy]

No.

You have to interpose the Jaycar unit in the wire from the speed sensor on the gearbox to the input on the cluster. The Jaycar unit's job is to adjust the signal going into the cluster.

Let's say that your speedo is currently reading 16% fast (4.11/3.54). The Jaycar box will take in the frequency of the sawtooth signal on its input line and feed out an output that is slowed down to get rid of that 16%. Effectively applying an 86% (ie, 3.54/4.11) factor to it. Or, given that you will likely be using a GPS speedo to work out what the actual vehicle speed is, some factor that is close to but likely a little different to 86%, which would also dial out the original speedo error.

[djvoodoo]

1 hour ago, GTSBoy said:

No.

You have to interpose the Jaycar unit in the wire from the speed sensor on the gearbox to the input on the cluster. The Jaycar unit's job is to adjust the signal going into the cluster.

Let's say that your speedo is currently reading 16% fast (4.11/3.54). The Jaycar box will take in the frequency of the sawtooth signal on its input line and feed out an output that is slowed down to get rid of that 16%. Effectively applying an 86% (ie, 3.54/4.11) factor to it. Or, given that you will likely be using a GPS speedo to work out what the actual vehicle speed is, some factor that is close to but likely a little different to 86%, which would also dial out the original speedo error.

Right, not sure if i explained myself correct. So wire in as below?

*edit, use accessory power to turn on the unit, i'll prob use the cigarette lighter etc, not pin 29 (ign)

 

Edited October 2, 2023 by djvoodoo