ABS fault 312, 322. 850 T5M 1994 MY Topic is solved

white 94 estate · Post by **white 94 estate** » 09 Sep 2018, 20:19

Hello

I was hoping for some assistance in recitifing a fault with my 1994 850 ABS. (OBD 1) - 355k
I have been trouble shooting a fault with the ABS AND TRACS lights on dash.

The fault appeared after parking the car for a week and after start up the fault was there.

Fault code 312 - Right front wheel sensor. open/short
Fault code 322 - 322 Right front wheel sensor, irregular >40 km/h

I can clear the first Code 312 but the 322 code won’t clear. Both warning lights can be intermittent and go off then return within a short drive usually after applying the brake.

I have inspected, removed and cleaned the ABS wheel sensor, checked resistance > 1000 ohms, inspected the wiring and connector which were in good condition and no breaks or Frey’s. I swapped out the sensor additionally with another and have checked the wiring loom back to the ABS computer for resistance 0 ohms found, the wiring runs in a continuous sealed loom which looked in very good condition.
I’ve inspected the contact ring on the wheel hub and found no breaks.

Unlike the later model ABS modules the early ATE modules seem to be very resilient, I am now guessing this is the only thing left to fault, but I’d like any other thoughts you may have before I commit to it’s replacement, are these repairable like the later, it has an all metal case unlike the later.

I have also realised I am over due for a brake fluid flush which I’ll complete in the next week not that I am having any breaking issues and pedal feel is good.

I realise this is my first post on here, I feel I have exhaustively utilised the search functions in the forums and I have found most posts refer the later model faults and not the pre MY 95.
I have found through searching the forums here first has often answered my questions so I have not needed to jump in previously. So thanks for the great input provided.

Regards
Rob.

Post by **Clemens** » 10 Sep 2018, 00:35

You´ve basically checked all the basics.
Do you have a chance to get an ATE ABS unit to swap in? I know they are not supposed to fail, but then they are over 20 years old by now.
My 95 had a similar issue that I never figured out.

One thing: Have you checked the wiring loom that goes into the ABS unit? On my 96 the insulation looked good, but as soon as I touched it the insulation crumbled apart revealing quite corroded wires.

white 94 estate · Post by **white 94 estate** » 10 Sep 2018, 01:44

Hi

Yes checked all the wiring and still in very good condition considering the age. I don’t have access to a spare module unfortunately so may have to purchase a new one or try to refurbish my current module. But I’d rather make sure first for obvious cost reasons.
Regards
Rob

Post by **Clemens** » 10 Sep 2018, 06:06

Don´t you have junkyards down under? Those modules are quite pricey, it´d be a shame to spend money on an unlikely part.
Still very strange that it happened while being parked which would make me believe it was a rhodant (or another freak-creature), but then you should be able to find a broken wire...

white 94 estate · Post by **white 94 estate** » 10 Sep 2018, 18:16

Yes breakers are an option, however ATE modules with TRACS are a little thin on the ground. A lot of POV packs with standard modules only.

Post by **Matty Moo** » 10 Sep 2018, 18:58

You can have an open circuit and still read full continuity. The problem is the wiring breaks inside the sheath, it will show a complete circuit when the car isn't moving but fluctuate open/closed when the car is actually moving.

They're the only wires on the car that move when the car does, they break.

white 94 estate · Post by **white 94 estate** » 14 Sep 2018, 01:48

Matty Moo wrote: ↑10 Sep 2018, 18:58 You can have an open circuit and still read full continuity. The problem is the wiring breaks inside the sheath, it will show a complete circuit when the car isn't moving but fluctuate open/closed when the car is actually moving.

They're the only wires on the car that move when the car does, they break.

Ok. As all the wiring looks to be in sound order and it’s probable there is a break within the sheath, how far back should I be looking at cutting back to effect a repair.

As I felt all was in order when I tracked the wiring back I had settled on attempting to locate a replacement control module.

Rob

Post by **Clemens** » 14 Sep 2018, 03:31

Rob, I think you can try to use a non tracs module for testing purpose. I´m not sure about that, especially since I never had a pre 96 module off the car. but I think you could get it on there. Tracs will not work, of course, but the ABS unit should.

white 94 estate · Post by **white 94 estate** » 25 Sep 2018, 19:29

Hi

Just an update if any interest, I have decided to purchase Part# 9442888 from Volvo, which is the wiring loom for the wheel sensor to the ABS module. I'll update on my repair attempt.

Thanks Rob.

Post by **abscate** » 26 Sep 2018, 05:07

Thanks for keeping us informed Rob.

That will help the next gal/ guy