ABS control unit repair - Page 12

NorfolknGood · Jul 6th, 2009, 09:21

Quote:

Originally Posted by Chris_Rogers

What have you to lose by trying?

When I fit my 2nd hand unit and if it works ok I will cut the old one apart and investigate it.

Grendel · Jul 25th, 2009, 20:32

Well I have just found this post and will definately be giving it a try as I have all of the classic symptoms, this post may have saved me from speding £100 on ebay to get a replacemet unit or more for a new one. I'll let you know how it goes.
Grendel

Grendel · Jul 29th, 2009, 20:57

well that was strange, I did the repair, then the lights still stayed on, until today, when I changed the seat position back to reclined and then back up, at the same time the wife was trying to shut the door and managed to trip the central locking, all just as I started the car, and miraculously the lights went out - fingers crossed they stay out now.
Grendel

Grendel · Jul 30th, 2009, 20:30

aargh- lights came back this morning, got the mitchell wiring diagram and metered the sensors at the plug - rear left open circuit, did some checking later and got open circuit at the plug at the back, so its either sensor or wiring, maybe I will pull the whole lot and check the wiring, I know where there are a couple of older 850's with ABS at a breakers, maybe I will be able to get the sensors from there. I cant find any rear sensors anywhere in the uk online.
Grendel

Chris_Rogers · Jul 31st, 2009, 08:24

Note the rear sensors are in a pair, they are not available separately.

You will find the wiring loom (to both rear sensors) has a connector under the luggage compartment floor where it joins the main loom , it may be worth a look there.

jdvickery · Aug 7th, 2009, 01:18

I'm still working on mine, S40 01, I found an almost new complete unit at a junk yard and I am thinking about doing the job of replacement module/pump myself. Question, when I disconect the brake lines do I need to have a "power flush" done to bleed the lines? Or can I bleed them using gravity flow?

Chris_Rogers · Aug 7th, 2009, 08:24

You will need to power flush them, however you don't need to change the hydraulic portion if the problem is with the ECU, this can be replaced separately.

JonYorks · Aug 7th, 2009, 14:16

I've had the tracs and abs intermittant lights thing for a little while so decided to try this fix, and touch wood so far its worked!
I didn't have a female torx socket but found that a normal 4mm socket worked fine on mine.

I did download this photo showing which are the common problem solders to re-do

Also while looking at the board I noticed another dodgy solder not mentioned. Its on the two square black things on one corner of board (one has writing on it).

I lighty touched one of prongs with screwdriver and it came away from the pcb far too easily. So I resoldered all 4 of these joints also.

wackojacko · Aug 7th, 2009, 17:14

Hi,

Just registered as a Member, and did this fix...

Car was showing intermittent odometer, No ABS and No STC. Found loads of dry joints, put it back in and is now good as new.

Thankyou for a very helpful guide.

Rovolver · Aug 7th, 2009, 18:48

I did the resoldering on mine last week..
Inside everything seemed to be ok..I resoldered the joints anyway..just in case.
My ABS and Tracs Off lights are still on.
I did check the sensors before with a mutimeter and the numbers were correct.

Any other idea on what else to check?
Does anyone know how to check the ABS pump?
Cheers

Jul 29th, 2009, 20:57	#113
Grendel Junior Member Last Online: Apr 13th, 2015 20:37 Join Date: Jul 2009 Location: Canterbury	well that was strange, I did the repair, then the lights still stayed on, until today, when I changed the seat position back to reclined and then back up, at the same time the wife was trying to shut the door and managed to trip the central locking, all just as I started the car, and miraculously the lights went out - fingers crossed they stay out now. Grendel __________________ volvo 850 2.5 Estate 1996

Jul 30th, 2009, 20:30	#114
Grendel Junior Member Last Online: Apr 13th, 2015 20:37 Join Date: Jul 2009 Location: Canterbury	aargh- lights came back this morning, got the mitchell wiring diagram and metered the sensors at the plug - rear left open circuit, did some checking later and got open circuit at the plug at the back, so its either sensor or wiring, maybe I will pull the whole lot and check the wiring, I know where there are a couple of older 850's with ABS at a breakers, maybe I will be able to get the sensors from there. I cant find any rear sensors anywhere in the uk online. Grendel __________________ volvo 850 2.5 Estate 1996

Jul 25th, 2009, 20:32	#112
Grendel Junior Member Last Online: Apr 13th, 2015 20:37 Join Date: Jul 2009 Location: Canterbury	Well I have just found this post and will definately be giving it a try as I have all of the classic symptoms, this post may have saved me from speding £100 on ebay to get a replacemet unit or more for a new one. I'll let you know how it goes. Grendel

Jul 31st, 2009, 08:24	#115
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	Note the rear sensors are in a pair, they are not available separately. You will find the wiring loom (to both rear sensors) has a connector under the luggage compartment floor where it joins the main loom , it may be worth a look there.

Aug 7th, 2009, 01:18	#116
jdvickery New Member Last Online: Sep 28th, 2009 17:16 Join Date: Apr 2009 Location: Dallas	I'm still working on mine, S40 01, I found an almost new complete unit at a junk yard and I am thinking about doing the job of replacement module/pump myself. Question, when I disconect the brake lines do I need to have a "power flush" done to bleed the lines? Or can I bleed them using gravity flow?

Aug 7th, 2009, 08:24	#117
Chris_Rogers VOC Member Last Online: Apr 10th, 2017 16:55 Join Date: Jan 1970 Location: South Kent Coast	You will need to power flush them, however you don't need to change the hydraulic portion if the problem is with the ECU, this can be replaced separately.

Aug 7th, 2009, 14:16	#118
JonYorks Member Last Online: Feb 14th, 2015 20:34 Join Date: Feb 2009 Location: Yorkshire	I've had the tracs and abs intermittant lights thing for a little while so decided to try this fix, and touch wood so far its worked! I didn't have a female torx socket but found that a normal 4mm socket worked fine on mine. I did download this photo showing which are the common problem solders to re-do Also while looking at the board I noticed another dodgy solder not mentioned. Its on the two square black things on one corner of board (one has writing on it). I lighty touched one of prongs with screwdriver and it came away from the pcb far too easily. So I resoldered all 4 of these joints also.

Aug 7th, 2009, 17:14	#119
wackojacko New Member Last Online: Aug 19th, 2010 16:40 Join Date: Aug 2009 Location: Maidenhead	Hi, Just registered as a Member, and did this fix... Car was showing intermittent odometer, No ABS and No STC. Found loads of dry joints, put it back in and is now good as new. Thankyou for a very helpful guide.

Aug 7th, 2009, 18:48	#120
Rovolver New Member Last Online: Jan 24th, 2013 04:07 Join Date: Jul 2009 Location: Surrey	I did the resoldering on mine last week.. Inside everything seemed to be ok..I resoldered the joints anyway..just in case. My ABS and Tracs Off lights are still on. I did check the sensors before with a mutimeter and the numbers were correct. Any other idea on what else to check? Does anyone know how to check the ABS pump? Cheers

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