Thread: D2a TD5 - no speed signal

Scott doesn't the speed signal come through slabs , i think a code read will be the best place to start other than that it's just guesswork

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I didn't realise that the speed signal went through the SLABS. I assumed rather the signal broke off and went to a variety of different places. So that's a handy start point, cheers.

IMO the most suspect is the road speed signal output from the SLABS, it's not easy to diagnose cos it's PWM signal switching between 0 and 12 volts at a frequency of 8000 pulses per mile so an oscilloscope is needed to check if it exists... the problem can be ''splited'' in 4 variants:
1. no VSS output from the SLABS => you need to replace it(let's hope not but quite unlikely cos then you should have seen the 3 amigos too), maybe a dry joint on that output
2. a bad contact/corrosion at the SLABS plug - output = C0504 pin 3(pink/green wire)
3. bad contact in header C0290 where it splits between all systems the wire comes directly from SLABS into pin 19 then it splits and goes to each system with same colour wire to all(let's hope not cos this header is embeded in a harness not very easy to reach)
4. interrupted wire between SLABS and C0290
see RAVE - Electrical library - connector views

code reading might not help you much just confirm the symptom, i presume you'll get "road speed missing" or similar fault code from ACE and engine ECU and no current code from the SLABS(maybe only some hystorical) cos if it was a bad contact in the wheels speed sensors input connector C0505 you deffinitely should have got 3 amigios and fault codes for all sensors.

I've got a Truespeed fitted somewhere along the way to correct the speedometer for the larger tyres fitted. I wonder if that is perhaps causing a fault, but I had assumed that this would be after the SLABS in the system and only effected the speedometer...

Originally Posted by twr7cx

I've got a Truespeed fitted somewhere along the way to correct the speedometer for the larger tyres fitted. I wonder if that is perhaps causing a fault, but I had assumed that this would be after the SLABS in the system and only effected the speedometer...

Exactly the answer to the question I was about to ask.
Id check the connections there first.
Maybe disconnect it if no poor connections found. This should at least give you a reading even though incorrect and rule out the SLABS.
Does the truespeed come with a bench test procedure?

I presume the truespeed is connected on the SLABS output between C0504-3 and C0290-19(third wire from the bottom, this pin can be other number in reality but the wire colour is the same) after that the VSS(vehicle speed signal) splits to all systems and if it's there it can be very suspect that there's a bad contact or something, i attach you the relevant part of the diagram, follow the pink/green path starting from C0504-3(this is the VSS) and you'll understand what i mean even if you are not electronist

TD5 Speedo correction - no not the boardies!

This link may help if you didnt install the truspeed yourself.
After reading this Id probably check you power connection to the truspeed first then go from there.

Cheers. Pretty sure that is the guide I followed when I installed it years ago. Will have a look over the weekend.