ABS - yes, I know...

[ChrisMClark]

I know it's been covered a few times, but I'm after an answer. My ABS light is on constantly. Just read the codes, and it's showing the following:

1-2-4: RH Rear wheel sensor-faulty signal at speed less than 25mh
3-1-4: RH rear wheel sensor-open or short circuit
3-2-4:RH rear wheel sensor-intermittent signal at speed over 25mph

Does this sound like a dodgy sensor? (it does to me, but I've been known to be wrong!)
ABS light was intermittent from when I bought it last December, but is now on permanently, which I understand could be a symptom of a faulty ABS controller rather than a sensor. Check sensor. Plug is connected tight...sensor can't be removed though, the retaining bolt is just that rusty. It started crumbling in my socket!

Edit: Should add, controller part number is 6849538, longer number above is 10.0941-0402.4 (no idea what that number is, or what it means!). Car is a '93 2.0 saloon, without TRACS.

[p fandango]

my money is on the common dry joint in the ABS ECU, that brings up the rear speed sensor fault but it lies lol. There is a thread showing how to fix it, but i don't know where it is (someone will find it)

[ChrisMClark]

Awesome. At least with it being an old one it's just screws to get in there, no hacksawing and resealing as I've seen elsewhere on t'internet.

Now where's my soldering iron......

[Volvostorm]

Yours being a '93 doesn't have the dry joint problem, so it could be a sensor gone down, also check the wiring to the sensors, I had a broken wire on my '95, it throw up a load of codes, not of refering to the problem!

[ChrisMClark]

That'd be a bonus. Will have to have a closer look at the wiring; seems a fair guess that if the wirings gone dodgy it'll be around the sensor area rather than anywhere else, right? Given that's where the movement is? A new sensor will only be about 12 quid from my local scrappy anyway. How the hell do I get the damn rusted bolt out though? And are the sensors the same for the whole 850 range? My local scrappy only has an estate in at the minute.

[Volvostorm]

And are the sensors the same for the whole 850 range? My local scrappy only has an estate in at the minute.


Yes, I can't see why Volvo would change between estates and 'loons

[ChrisMClark]

Just had a scout and the part numbers seem the same rihght the way across the range, except diufferent parts for front and rear obviously.

Any suggestions for getting that poxy bolt out?

[Volvostorm]

Soaking it in wd-40 for a few days before trying to change it, I've not yet had the pleasure of tackling that bolt yet!

[ChrisMClark]

Not sure what this forums rule is on swearies (I'm on too many forums!)...

...but that bolt is f***ed. I'm thinking mole grips, WD40 and maybe a blow torch :D

[Volvostorm]

As long as you get the thread to come out, I don't think it matters how you get the bolt out ;)

[ChrisMClark]

PE4 (http://en.wikipedia.org/wiki/PE4) then? :D

[Volvostorm]

LOL! That should shift it

[nobananas]

The rear sensors are directly connected to their wiring (ie they don't unplug down by the brake backplate) and also joined together at the multiplug which is inside the car, under the bootfloor panel. The wiring comes up through the same plate as the fuel pump wiring (round plate that covers the fuel pump) and when I did mine I had to drop the fuel tank slightly to get the wiring through. What I did manage to do though was seperate the wiring at the multiplug (removed the pin connectors inside the plug) so I could replace one sensor at a time and hold on to the other one for future repairs. You can test the sensors using a multimeter connected to the sensors terminals and jack up the rear and have someone turn the wheel very slowly and you should get a pulse on the meter (lowest mv setting, easiest with an analogue meter)

[ChrisMClark]

That's odd mate, there's a connector plug on the sensor on mine!

[nobananas]

That's odd mate, there's a connector plug on the sensor on mine!

Wish there had been on mine ! LOL !. I can only think that the difference is that yours is an earlier one, mines a 96'

[ChrisMClark]

Quite possibly Bud, the Haynes manual says the following on removing rear wheel sensor:

"On certain models it will be necessary to trace the wiring back until the connector is located and can then be disconnected. This may entail removal of the rear seats or luggage compartnment trim panels."

Looks like I've been lucky! Wish I'd been as lucky trying to find the part. I've found tons of front wheel sensors, but none for the rear, and I really don't want to go to a main stealer for it.

[p fandango]

Looks like I've been lucky! Wish I'd been as lucky trying to find the part. I've found tons of front wheel sensors, but none for the rear, and I really don't want to go to a main stealer for it.
i'd be tempted to give Rufe (http://www.vpcuk.org/forums/member.php?u=544) a try, does very good prices & might be cheaper than you think

[ChrisMClark]

Will do, to be fair I've never been to a Volvo main dealer, so my comment wasn't really fair :lol: My experience of Fiat main dealers has left me rather jaded I'm afraid!

[p fandango]

Will do, to be fair I've never been to a Volvo main dealer, so my comment wasn't really fair :lol: My experience of Fiat main dealers has left me rather jaded I'm afraid!
Volvo main stealers don't seem to be that bad, prices for your everyday bits for an 850 are (as a rule) getting cheaper as they get older. I know what you mean tho i've had a few issues with some in the past, one even tried to tell me the R front bumper is a normal bumper with a seperate add-on lip lol

[ChrisMClark]

I had one Fiat dealer tell me that Fiat never made a 1.2 Stilo...funny I said, as that's what mine is. They didn't believe me and insisted it was a 1.4 until I showed them my V5.

[Flatout Phil]

i'd be tempted to give Rufe (http://www.vpcuk.org/forums/member.php?u=544) a try, does very good prices & might be cheaper than you think

Seldom bother with anyone else for Volvo stuff. Can't be beaten and a real decent bloke.

[bobbych]

I did my sensors on my 94 a few weeks back. I only needed to change the LH, but they come as a pair. What I did, was find a pair on ebay, for £5, and then set about changing the left. ON removal, the LH sensor bolt sheared. I also had to remove the brake disk, so i could get to the front face of the sensor, and using a hammer and bar, had to drift out the sensor as it was siezed in there. But it came out. As for the sheared bolt, there was not enough shank left to do anything with it, so i left it. I found the replacement snesor went in, and does not really need the bolt as it is a tight fit, so I never did anything with it.

Anyway, with the sensor out, you simply trace it. the RH you have is easier, as it simply goes up, the front of the fuel tanks, and comes out into the boot, from under a round panel, and then goes to a connector on the RH rear wheel well. it is a yellow connector. What I did, was open this connector, which is easily unclipped and opened, and removed the two wires from the LH sensor [the one i needed to change, you will need the RH ones out] and left the other 2. this way you can feed the wires out through the boot floor. TOP TIP< before pulling out the cables from under the car, tie some string to the end. it makes feeding back the new cables a doddle, otherwise you will be fishing about around the fuel tanks for ages.

the whole job took me around 3 hours, inc stripping down the brake and rebuild. remember, you need to drive the car faster then 25mph to reset the ABS light.

As you have the 93 car, as said, your ABS ECU is very robust, and most failires, are indeed with the rear sensors.

[bobbych]

coulpe of pics of my hub stripped with ABS sensor on my page here, page 9

http://www.volvoforums.org.uk/showthread.php?t=84260&page=9

[ChrisMClark]

Cheers Bobby. Like I said, I'm lucky in as much that the sensor just unplugs at the hub. Problem is of course trying to fit the replacement which may have a long wiring loom on it.