S15 Tacho/RPM not working - Strange wire

[Joeh]

Hi all
Thank you for taking a moment to read my issue with my car

My car is currently not registering anything on the RPM gauge/tacho. I have not had a chance to check with an alt-meter if the signal is correct from the ECU as I'm not sure which wiring to check.

The car is running a chipped ECU (standard ECU chipped).

There is a strange white wire which was crimped to a white/purple wire on the dash harness and has a label in Japanese saying "Warning, Do not cut this wire" - unfortunately someone has already got to it as I found it connected to.. nothing.. behind the head-unit. There is a small capacitor/resistor which is in the little box in the picture - the box is labled "s sens" - I'm guessing for - Speed Sensor.

I've attached some images in case anyone knows what it is for and if it is related

Many thanks
Joeh

 

[Joeh]

Just to confirm the speedometer is working fine and everything else is also working perfectly - its just the RPM not being displayed

Thanks again
Joeh

 

[craig8585]

Maybe a faulty gauge cluster mate. I'm sure people have had similar issues in the past.

 

[Joeh]

I hope not !!!!! But thanks for that - I'll see if I can get another one from somewhere

I read something about another member putting the cluster in Diagnostics mode - is this possible without a diagnostics machine?

 

[craig8585]

I'm not sure you can do a diagnostic check on the cluster..? Not heard that one before.

See if someone local to you would let you swap clusters.. Free diagnostics!

 

[Joeh]

Sounds good to me
I don't know anyone here though d:

Maybe a post in the chit-chat section?

 

[craig8585]

Where are you from?

 

[Joeh]

Hendon in London

 

[craig8585]

I'm fairly sure there are a few members around there. Otherwise, japperformanceparts often sell clusters at decent prices.

 

[Joeh]

Thanks! Will give it a shot

Joeh

 

[DeanS15]

sounds like someone had a rev sensitive turbo timer fitted which would explain the wire tapped into the rpm signal - maybe the end of the wire has earthed and killed the rpm sensor in the ecu - just a theory but i reckon it sounds likely with what you have...

 

[Joeh]

Oh no! That is a possibility then as it did have a turbo timer before I got the car...

Would it be tapping into the correct wire though?

 

[meddler]

There is a diagnosis mode in the manual in the Electrical section page EL-64. Let us know how you get on with it. I would like to know how you go with the diagnostic steps.

 

[Joeh]

Thanks for that - Glad I downloaded the manual yesterday !

I'll give it a go in about an hour and post up how it went

Joeh

 

[Joeh]

Tried it and it worked fine - Steps are very easy and heres a copy for anyone else trying to do the same - took less than 10 seconds really and worked first time.

1. Turn ignition switch to ON and change odo/trip meter to “TRIP A” or “TRIP B”.
2. Turn ignition switch to OFF.
3. Turn ignition switch to ON when pushing odo/trip meter switch.
4. Confirm that trip meter indicates “0000.0”.
5. Push odo/trip meter switch more than three times within 5 seconds.
6. All odo/trip meter segments should be turned on.
NOTE:
If some segments are not turned on, unified meter control unit with
odo/trip meter should be replaced.

At this point, the unified control meter is turned to diagnosis mode.
7. Push odo/trip meter switch. Indication of each meter/gauge should be as shown left during pushing odo/trip meter switch if it is not malfunctioning.


- I guess its time to check the wiring for me

 

[Joeh]

I have to comment on the quality of the workshop manual it is truly excellent!

This is for anyone who may have the same issue or came across this thread through google:

 

[Joeh]

Okay I've checked the connection I'm getting 0.08v at idle and it does increase depending on rpm.. but only small amounts like highest I've seen without reving hard was 0.23

Doesn't seem like enough voltage - so I disconnected the cable from the ECU harness and checked it again from the ECU side with nothing connected and it was the same

Any ideas.. maybe its connected to the wrong place on the ECU although it does vary?

Joeh

 

[Joeh]

Okay checked it again today - idle at 0.23v

Still too low!

Anyone know what I can do to fix this? Had a quick look at the ECU can't see any burnt resistors/capacitors etc.

Joeh