help needed early 850 abs,reward offered!

[duke1]

hi all well it seems my car is truly possessed and even the mot station cannot exorcise the evil one(abs warning light) passed on all but the evil thing.
so far i have
replaced broken rusty reluctor rings on front and fitted 2 new front speed sensors.
cleaned and tested rear sensors,rings look good,tested at junction in the rear compartment and again at main abs module connections all read as expected.
fitted recon abs pump from good german supplier
fitted tested and warranted abs module
thoroughly bled system,good brake pedal.
checked and cleaned all fuses.
replaced abs relay.
removed and tested brake position sensor using ohm meter which rises from 1ohm through to 8 ohm when manually operated which i think means it is working?(it is the one on the booster under master cylinder)
i did try the ignition key wiggle but it seems to be very good and no obvious fault.
i have tried everything and no garage will help as they cannot just plug in obd2 please can anyone help,what else is there that will trigger the evil one?what am i missing?marbles maybe.....?

[Bob]

The ABS light came on my 1995 850 T5 some years ago and the garage said there were 7 fault codes, and that it was a wiring fault , so would have to trace all the wiring. I said what wheels are affected, and front n/s was one. I said no to all his suggestions. I said it was the module.

I contacted BBA Reman and they had one for my car and sent it to me, just over £400 with shipping. Fitted it, job done. Sent the old one back and have life time warranty on the one they sent me.

They repair all sorts of electronic kit.

Bob

[Luxobarge]

If it were me, I'd do whatever it takes to be able to read the ABS codes, and go from there. There's an old saying in the trade - "guessing is time consuming and expensive" and without wanting to be insulting, all you've been able to do so far is guess at the fault, pretty much.

I'm not an expert on how to read codes on an 850 (mine's a V70 and OBDII compliant) but perhaps other more knowledgeable folk on here can tell you what you need to do to be able to read ABS codes on your car, that's the route I think you need to go, as you appear to have done pretty much all the obvious things. If you can read the codes, and you get a consistant single code coming back after clearing it each time, then that's going to be a major pointer to the source of the problem. If on the other hand you get a load of random codes, then that at least indicates a different type of problem, often voltage related.

Hope that helps!

[Simmy]

you need some one with vol fcr diagnostic or an old snap on reader that can read obd 0 the plug socket is under the coin holder or your car may have the flash code read system in a small box under the bonnet.

[Luxobarge]

Originally Posted by Simmy

you need some one with vol fcr diagnostic or an old snap on reader that can read obd 0 the plug socket is under the coin holder or your car may have the flash code read system in a small box under the bonnet.

Brilliant, thanks Simmy. So start by telling us whether you have the OBD socket under the coin holder or the (earlier I think) flash code arrangement in a small box under the bonnet as above.

[Simmy]

i have the obd socket in my 94 850 t5 but you need the right equipment to read from it its NOT obd2

[duke1]

Originally Posted by Luxobarge

Brilliant, thanks Simmy. So start by telling us whether you have the OBD socket under the coin holder or the (earlier I think) flash code arrangement in a small box under the bonnet as above.

hi yes i forgot to say in my op that this car has the flash code system and only codes seem to be nonsense ie i have 141 and 142 and 212 none of which are listed as abs codes.
i have looked and see no socket for obd2 inside the car so maybe it is too old for this.
i know it sounds like i been guessing and tbh thats not far off the mark,but in my defense an awful lot of information when searching the abs refers to the later type a.t.e system common faults which lead me down the path of faulty abs module solder joints and rather than that i bought a used unit so i could try that and still have a unit to send for repair as they will not repair a unit thats been opened.
when that did not work i tried the other obvious cheap bits like the abs relay and only decided to replace the pump as the original had some sort of fault as 12v supply to the motor would run it then wouldnt then would intermitent so i decided some of the windings must be burnt out.
i did test sensors with multimeter and replaced due to one having been struck by the broken reluctor ring,not my area of skills sadly as abs was rare and new when i was apprentice,all else sailed through mot so this is a real pain,tomorrow i am going to take off the brake position sensor and see if its broken as in several threads here,last ditch effort before i burn it!

[Baffler]

Originally Posted by duke1

hi yes i forgot to say in my op that this car has the flash code system and only codes seem to be nonsense ie i have 141 and 142 and 212 none of which are listed as abs codes.

Taken from Volvo / Pocket Data Booklet Cars / 850 / Diagnostic Trouble Codes / ABS

141 = Faulty pedal sensor, shorted to ground or supply.
142 = Faulty stop (brake) lamp switch, open circuit or short circuit.
212 = Right side front wheel sensor, no signal when moving off.

Have you tried to delete these codes and see what comes back? I can't remember the erase procedure so maybe someone else can advise how to delete via the engine bay port.

And have you tried the cardboard/wedge trick between the multiplug and module or is it very different on early Alter 2 cars?

Also, given the amount of parts you've changed out I'm wondering if this could be a wiring/multiplug issue and a possible cause for your intermittent 12v supply? You may need to test each wire/connection for continuity and monitor resistance across each one or, at least, open up and inspect the harness for physical damage.

[Luxobarge]

Baffler's post above seems very helpful to me, IMHO what you need to do now is find out how to clear those codes, then run the car to see what comes back. Can anyone here advise on how to clear codes from the "flash code box under the bonnet" system?

If the same codes come back, then it seems to me that you need to focus attention on a) the brake pedal switch and possibly wiring and b) the front right side ABS wheel sensor and possibly wiring. Remember, just because you replaced the sensor doesn't necessarily mean that it's a good one. If that 212 code comes back I'd be tempted to either replace that sensor with another one, or better still swap the right and left sensors around and see if the fault moves to the left wheel.

First thing is to clear codes and see what comes back though, otherwise there's a very real risk that these codes will be a red herring.

By the way, congratulations for staying with this fault and putting in all the effort, I know how incredibly frustrating these kinds of faults can be, but I bet you've got an otherwise sound car, and you WILL get there in the end. Keep up the good work!

[Derek UK]

Checking around I found this https://www.youtube.com/watch?v=5V0NQau6-F8 Yes it is using the OBDII socket but a comment was made about codes being cancelled from storage after a 35 mile run and 3 cycles of running. The stored fault code will then be cancelled if the fault has gone. After doing the repairs you have done the fault may have gone but the code is still stored. A small trip and a few restarts might put the light out. Please tell me if this is all nonsense!!