Volvo 850 ABS warning light advice

reptar · Post by **reptar** » 27 Jan 2012, 20:05

Dear Volvo enthusiasts,

I own a Volvo 850 1997 B5252FS with AW50-42 auto transmission.

I have recently installed a new engine into the Volvo as the previous owner had cooked the engine due to a failed water pump.

I started the cars ignition with all instrument cluster warning lights off except one; the ABS.

I purchased an OBDII Memo Scanner and with the car running, no fault errors were detected.

I have cleaned all four wheel sensors and all four pulse discs from dirt and grime and still the ABS warning light remains lit and still no errors detected using the Memo Scanner.

I took it for a spin around the block (car runs great) in the last efforts to see if this would fix the problem, but with no luck. Can the ABS system be reset?

Any advice would be greatly appreciated as I would like to have the car road worthied and I doubt they will pass this.

Cheers,

Post by **Matty Moo** » 27 Jan 2012, 20:13

A generic OBD scanner won't read ABS codes. You either get the Volvo software that will, or something like an Autel eu702.

You can't really "reset it". Even if you had a scanner that can read/erase ABS codes it would still trigger as soon as it found the problem again. If no problem is there, the lights go out. It does a self diagnostic at start-up for continuity and then another at 8mph. If it's the original module in the car, then maybe it's time is finally up.

reptar · Post by **reptar** » 27 Jan 2012, 21:23

Thanks for your help. I think I might purchase the Autel eu702. At least this will be useful in the future in finding detailed errors. The modules go for about AU $250 + and I could spend the money on this instead only to find out that the light is still there. I think it's better to find out the source of the problem first.

Cheers!

ArchieBrown · Post by **ArchieBrown** » 27 Jan 2012, 22:12

Hi,

It may be worth reading this: https://www.matthewsvolvosite.com/forums ... =1&t=12651

Apparently the ABS modules all go eventually and if you're up for it you can fix it yourself. Reading that post and replies may save you from some of the schoolboy errors I made when I did it.

Arch

Post by **precopster** » 27 Jan 2012, 22:49

Do you have the ABS unit which has the large steel connector on top or is yours one of the upside down units with E torx screws underneath?

I have software that can read your car so if you want to travel to Preston I'd be happy to read it free of charge.

reptar · Post by **reptar** » 29 Jan 2012, 15:47

Thanks ArchieBrown,

I have taken the ABS module out. Will inspect this further for burn outs soon.

Thanks for the offer precopster.

Post by **precopster** » 29 Jan 2012, 17:02

No problem. The offer's there if you need it. What area of Melbourne are you in?

If you have Vol FCR software with a cable that's enough for your system. There's one on eBay US at the moment. I think it is $44. You'll need an older laptop with a serial port or a USB to serial converter. The Autel's or any other scanner can't deal with faulty solder joints so best to do this first.

With a magnifying glass inspect the solder joints as in the article. Reflow them with a 25W soldering iron (no hotter for the small lands and keep your iron clean by filing the tip clean & wiping on a moist towel or sponge while hot)

I always solder suck the old lands and reflow with all new solder. If this doesn't work have it read. In my case we had a faulty pedal height sensor which is just in or behind the booster.

reptar · Post by **reptar** » 04 Feb 2012, 13:43

I have purchased a serial diagnostic cable for the Volvo 850 and a serial to USB converter. Am I correct in thinking that all i will need is the VOL FCR software installed onto my laptop?

I removed the ABS control unit and inspected the solder joints. No apparent signs of burn outs however, the positive/negative wires running from the pump into the module appeared to have been overheated/overloaded as their outter insulation was exposing actual wire. (This was elimated in the next step)

I installed a completely seperate ABS module/ pump the other day. Pressure bled the breaks, fired her up and still the ABS light remains lit. We took it fo a spin and still lit. What are the chances of two faulty modules? The car it came from had apparently done 140k clicks.

Behind the break pedal appears to be two sensors (one above the other). I was able to check the lower with a multimeter and all seems good. Not sure what the above sensor was? (had many more wires going into it then the other). This sensor appeared to be operating correclty with compressions of the pedal so I left it.

I am now waiting for the cable to arrive in the mail to run this diagnostic check. I should take bets. I am stumped!

Cheers,

Post by **Matty Moo** » 04 Feb 2012, 14:26

Any used module is likely no better than what you already had.

Post by **taxi** » 04 Feb 2012, 14:50

If the ABS light is lit with no codes, wouldnt that also indicate a faulty ignition switch?