Speed Reading Intermitently Working

[.:: GimpS-R34 ::.]

So noticed last week when going to get fuel the speedo wasn't moving. Checked the Power FC to get the reading. It also read 0. I noticed on the way home though that both Speedo and Power FC now were displaying correct speeds.

Took it to the mechanics for a few other maintenance items and yet again speedo stopped working. Assumed from here it was the speed sender behind the gearbox. Just had a replacement installed at mechanics and no dice. Mechanic traced the wire all the way to the loom and no splits in the wire.

So what options can there be to look at or anyone else experienced similar, and best profession to look into it ie. Auto elec?

Details if required

R33 GTR

Nismo Dash

Power FC D-Jetro

[Tommy Kaira RL]

If they both stop working at the same time then it probably would be the speed sensor from the gearbox.

[.:: GimpS-R34 ::.]

That was my first guess.. Replaced and still no go

[89CAL]

Dirty connection somewhere is my bet. Keep in mind that the speedo signal goes to the speedo before the ECU so if it is cut pre speedo, neither will work

I would check your connections from the gearbox loom and clean them if needed.

I have an R33 wiring schematic but it might not be relevant to the r34

[.:: GimpS-R34 ::.]

It's R33 mate.. Interesting. I was under the assumption it went to ECU first. Would be interested in the schematic. Auto elec might be the first port of call then. Try track down where the fault starts

[89CAL]

Sorry, was on mobile and could only see your name there, so figured R34.

I can have a look at the wiring diagram tomorrow morning and give you some info if you want. Because its not happening all the time, and when it does work the speed reads right (correct?) I'm assuming its a dirty/loose connection somewhere along the line or perhaps the early stages of a rub through/short.

If you have a multimeter, I'll give you some places to start. Probably re-do what the mechanic did but its best to know for yourself

[Tommy Kaira RL]

This should help you out.

Doc1.docFetching info...

[.:: GimpS-R34 ::.]

Yeah Callan I assume speeds were correct. They seemed to be the speeds I thought I was going. It stopped working. Then on way home worked. Worked all the way to mechanics. Stopped working while at the mechanics. Replaced speed sensor. Still no go

Cheers Brad. Will have to just start crossing off the list I guess. Is there a way to ensure the replacement speed sensor is indeed working correctly?

[Tommy Kaira RL]

The speed sensor would probably be ok when replaced. Next step would be to see if you get 0-5v at the ecu at pin 53. Then at least you know the signal is or isnt getting to the ecu.

[89CAL]

I think you need an oscilliscope to test the speed sensor properly. Give me 10 mins and ill dig up some drawings

[89CAL]

O.K I have had issues in this area before with my reverse lights. They worked intermittently (funnily enough) and I bought a new reverse switch but discovered the problem before I put the new switch in. Reverse lights would flicker on and off etc

I've circled the speed sensor plug (top of drawing circled in black) and the plug I had problems with (was just dirty, cleaned it up, checked connections were good)

And in the next one it shows the same thing but in a wiring schematic, just so its easier to work out which wire is which. Its pretty easy looking at the plug to work out which wires are which. Just hold the plug and look at it in relation to which side of the plug on the drawing. If you need a hand I can help anyway. Ive marked around the plugs and put dots where the wires for the speed sensor are

Just found this as well, shows the speed sensor drawing as well

Edited March 7, 2015 by 89CAL

[.:: GimpS-R34 ::.]

Awesome. Cheers guys. Will start diagnosing and see where I get

[89CAL]

Those 2 plugs (first diagram, circled near the relay box) are where my problem was with the reverse lights. They were gunked up with crap. Gave them a clean and came good

[.:: GimpS-R34 ::.]

OK, Bt of an update. Auto elec mechanic found a crack in the PCB and that has been fixed. All electrics checked apparently.. But still no speed. They can spin it manually and the speed goes up but no reading from car

Is it possible to get different speed sensors? He asked if I got an auto or manual sensor for replacement. Rang mechanic and said the only thing that was different was the gear on the end but he swapped them over so it has my original gear in it..

I'm going back to mechanic tomorrow to put original speed sensor back in just incase but any thoughts?

[.:: GimpS-R34 ::.]

Bought a new cluster and I get the same problem. Wires have all been checked by auto electric mech.. but I cant say 100% as im just relying on what they say.

Now the speed sensor that was bought had a different cog on it. And seems it is also in a different position. So there is more than one speed sensor type for a 33gtr?

Wreckers only had that one speed sensor so what is the best way to aquire the correct speed sensor as i feel this is still my issue?

[.:: GimpS-R34 ::.]

Alternatively. Is there a way to change the location of the shaft on the sensor? The replacement i got is offset the wrong way to fit a bigger cog. Is it possible to reposition it?

[MozzMann]

In some cars any ferrous metal debris floating around in the Trans can effect the induction pick-up and thus the speedo actually working

based on your latest discription it would seem there is no voltage supply to the induction sensor, remember these are essentially a Variable DC Square or Sine wave generator BUT will not work if there is no DC supply to the Sensor AND it the sensor is not adjusted correctly (this varies from 5-10 Thou to as much as 30 thou depending on the sensor and gearbox)

[sonicz]

Have you checked that the fusible links are in good order? I have seen them mess with instrument gauges.

And by this I mean that they are making good solid contact and there is no corrosion, not just that they are not broken.

Edited April 8, 2015 by sonicz

[89CAL]

  On 07/04/2015 at 11:21 PM, MozzMann said:

In some cars any ferrous metal debris floating around in the Trans can effect the induction pick-up and thus the speedo actually working

based on your latest discription it would seem there is no voltage supply to the induction sensor, remember these are essentially a Variable DC Square or Sine wave generator BUT will not work if there is no DC supply to the Sensor AND it the sensor is not adjusted correctly (this varies from 5-10 Thou to as much as 30 thou depending on the sensor and gearbox)

This is true with non contact sensors, but I believe because the R33 use a driven speedo sensor it is not an issue

[MozzMann]

Oh OK I thought the Manufacturer was using an induction pickup off the output shaft of the box like most cars from about '95 onwards