ABS TRACS lights coming on intermittently
 

The dreaded ABS TRACS lights have been coming on intermittently. The brake pedal can sometimes buzz before they come on. If I'm using the car the next day, the lights will be on upon starting, then go off after a few seconds and stay off for a few days, until the cycle repeats.

My ABS module was rebuilt in Jan 2023, along with the o/s/f ABS sensor replaced with a new one. In July 2023, I had the n/s/f ABS sensor also replaced with a new one. I took the car back to the indy I've been using for the past couple of years who carried out the work. They have checked the reluctors, speed sensors etc and both the wheel bearings are new, but can't find a fault via a scan. They said the lights need to stay on permanently for the scanner to pick up any errors. *** I had the wheel bearings done at a different place who noticed the ABS TRACS lights came on, so they did a scan and they said it pointed to an issue with the ABS module ***. If it was the module, then surely my usual indy's scanner would have picked it up. I feel a bit fobbed off by them (I'm sure that's not the case), but if they can't find a fault, then I guess they are stuck too.

I'm bit concerned that MOT time will be coming up in a few months. I really don't want to scrap the car. Not due to the fact I've spent quite a bit of money so far putting things right when needed, but it's my first Volvo (V70R) and I really like the car.

So, I'm in a dilemma. I was thinking of buying another working ABS module, get it fitted and see if that solves the issue or bank on the lights not coming on at MOT time. Very unlikey the latter will happen due to sod's law.

Your helpful thoughts as always please.

Hi

Depending on year of the car, you could buy a cheap OBD bluetooth dongle for about £8 and a mobile phone running the free Torque app or the 850 OBD-II app (for early models)), and catch the code when the light next comes on?


Steve

Hi

And I believe you will have rear wheel speed sensors as well as front.

https://www.pelicanparts.com/techart...eplacement.htm

Steve

Hi SteveSarre,

Thanks for your replies. The indy has checked all the speed sensors, reluctor rings, ABS sensors, everything. I do have a OBDII reader with the Torque app and there was no code captured even when the ABS TRACS lights are on. Driving her yesterday, I noticed I lost the speedo (rev counter was still working). The speedo came back after switching off and on the engine and the ABS TARCS lights went out.

I found the following thread - https://www.volvoforums.org.uk/showthread.php?t=191451 and going to try the plastic/cardboard wedged in between the ABS pump and module fix via this link - http://www.carinstructions.com/volvo...70-abs-module/

Upon looking at my ABS pump and module, the wire block connecting into the pump is exposed. Looks like the cover is missing (circled in the photo) and secured with a grey zip tie. I wonder if dirt has entered the wire block connector and causing the intermittent issue. Should I use switch cleaner to clean it out? How should I approach it? Can I still wedge a plastic credit card in between as per the http://www.carinstructions.com/volvo...70-abs-module/ link? Looking at the fix in the photo, the piece of black plastic is wedged between the ABS pump and the black cover for the wire block connector. What would the plastic credit be wedging between if my cover is missing?

That means that your scanner isn't picking up the codes, if the light is on there WILL be a code, maybe you need a different method of reading the ABS codes?

Losing the speedo is actually a good clue, as it's driven by the front left ABS sensor. Of course the fault could be in the wiring or the module, but at least you know that there may be a fault in that area.

Don't worry too much about the plug cover, they're fairly fragile and break, mine did and I also just have it tied on over the plug to prevent splashes getting into the connections.

Yes, I should think you can still try the wedging technique without the plug cover, IIRC on mine there's still something to wedge against.

HTH :teeth_smile:

Thanks Luxobarge, should I still clean that block connector? Shall I wedge say two credit cards into this space (arrowed)?

Yeah, cleaning it can't do any harm, and it'll more than likely help. While you've got the big plug off, there's a little (I think white) 2-pin connector that provides the main power to the ABS, that sits next to it. Give this the most attention, I've had a lot of problems on mine with it not giving a decent connection, and therefore supplying dodgy voltages to the ABS module, Clean it thoroughly, perhaps tighten up the connectors if possible, and re-seat it multiple times (ideally soaked in contact cleaner). Don't use WD40, it'll likely make the contacts worse.

Yeah, I reckon put in as many wedges as you like, until it feels firmly wedged!

Thanks. So, I need to unclip both the wire block connectors arrowed 1 and 2 and clean with contact cleaner. Is the 2-pin connector providing the power arrowed number 2? That's the only one I can see.

What is actually being wedged? If that multi-coloured wire block connector is being wedged away from the silver/grey metal pump, is that making sure the wire block connector is seated into the slot of the ABS module so it doesn't move?

ABS module now wedged. Will see how the ABS TRACS lights behave until I get some contact cleaner to clean the connectors.

Yes, that's the dodger I was talking about.

Yes, you've got it. I think the idea is that if there's a bad connection or bad solder joint it pushes them together more firmly by sideways pressure. Personally I'm not totally convinced about this "fix" but probably doesn't do any harm, and there seems to be plenty of experience on here that says it can work.

Further update ....

I managed to get to the wire block connector and the smaller 2-pin power plug on the ABS module and cleaned the connectors and sockets they plug into with WD-40 contact cleaner. I left the piece of plastic wedged in. These are the results:

1. Upon turning on the ingnition, the TRACS light went out immediately but the ABS light stayed on.

2. Turned on the engine and the ABS light is staying on.

3. I went for a test drive and the speedo wasn't working. The ABS light stayed on throughout the one hour drive. The TRACS light never came on.

4. I tried turning off the TRACS via the dash button, but the TRACS light didn't come on. It would stay on until I took my finger off the TRACS button.

5. On the test drive, I didn't get the buzzing or vibrating sound from the brake pedal below 30MPH as I have been previously.

6. Switching off and on the engine hasn't made a diiference - the ABS light is still permanently on.

7. At home I connected my OBDII connector and did a scan with the Torque app with the ABS light on. The scan said no faults were found in the ECU.

I've taken out the piece of plastic wedging for now and will take her for another drive to see if the first issue of both ABS and TRACS come on and off intermittently again or if just the ABS stays on permanently. If the the ABS light still stays on permanently, I hope the indy's scanner will pick up a fault. I sense the ABS module could be faulty. I may have made things worse by cleaning the ABS module connectors :(

Luxobarge - many thanks for your replies with very helpful tips.

You're welcome, I've had a lot of trouble over the past couple of years with intermittent ABS light on mine, which I THINK I've just fixed by replacing both ABS reluctor rings. My fault was intermittent though, sometimes it would do several journeys without fault..

OK, so the speedo is driven by the front left ABS sensor, so with no speedo this is a huge indicator as to where the problem is, it appears to be not getting a pulse from that sensor. In the absence of codes to confirm it, I'd say that's where your fault is. Personally I'd leave well alone at the module end, and have a look at the front left sensor, start by cleaning it and checking the reluctor ring very carefully (I'd recommend a bright light and magnifying glass) or possibly replacing that sensor to see if it cures the problem. It's still possible that the fault is at the module, but less likely.....

It's a shame you can't see the codes, there WILL be one there.

By the way, when you have an ABS light on, it's there because of a detected fault obviously, and will stay on for as long as the fault is there. However, if you fix the fault, or the faault disappears for some reason it will still show the fault light until the ABS has done a successful self test. This includes the car needing to be driven at above 15 mph, so you will always have the light stay on until you've exceeded 15mph, at which point if the module hasn't detected a fault it will put the light out.

Hi Luxobarge, it is shame I can't read any fault codes with my OBDII reader. Can you recommend one that won't cost hundreds of pounds that can read codes off a 1998 vintage? I'll have a go at cleaning the left ABS sensor first. It 'should' be fine as it is new and was only installed in July 2023. The front reluctor rings I've had checked and were reported fine. Are there any more differences between the left and right front ABS sensors, apart from the left one driving the speedo?

As someone who hasn't tinkered with cars much in the past, it's been interesting troubleshooting this issue and means I've got to know the car a bit a more :) Wish I had more time to do it. I thought getting a pre 2000 car would be simpler to maintain than the overly electronic modern cars, how wrong was I :) However, I do really like the car and plan to keep her going for as long as possible. This forum is a great resource for advice and tips from the likes of your good self and many others who contribute.

OK, so I'm not an expert on diagnostic systems for these cars, but I believe I'm right in saying that an ELM327 dongle (plugs into the OBDII socket and communicates via bluetooth) can be had for around £20, and then you'll need the Volvo 850 OBDII app for android phone - a couple of £ I believe.

Now this is interesting, as I too have a persistent intermittent ABS light, and having done all the obvious things I'm taking my own advice and finally getting the above dongle so that I can read the ABS codes too. Mine's a 1997 V70 T5, and like you I've found that my generic OBDII scanner is fine for engine codes, and possibly gearbox although I've never tried, but won't do ABS, SRS etc.

I've ordered it, and it should be with me in a couple of days, so when it arrives I'll have a go at downloading the app onto my phone and see if I can get it to work. Member 4x4 on here seems to know a lot about the various diagnostic tools available, so I'm following his guidance here, given to another member on another thread, where (with reference to the dongle) he says: This one will work https://www.ebay.co.uk/itm/125378422912

I wanted to follow his recommendation as apparently not all ELM327 dongles are the same, some work better than others it seems.

I'll let you know how I get on. :teeth_smile:

OK, there's another thread on here about ABS light by Duke1 who said he'd put a new sensor in it. However, when he found that the code consistently pointed at that sensor, he had another look and found that being an aftermarket sensor it had a slightly different plastic moulding shape where it sits in the steering knuckle, something like an extra bit of plastic was protruding, and preventing the sensor from sitting down properly, so it didn't work. I think he removed/smoothed the extraneous bit of plastic so it sat in its mount properly and the ABS light went out and stayed out. If you've fitted a "new" sensor, worth checking this very thoroughly IMHO.

This is the thread from Duke1, well worth you having a read through this:
https://www.volvoforums.org.uk/showthread.php?t=335591

Thanks Luxobarge, I read Duke1's post and it does sound similar to my issue in that we both have an aftermarket ATE ABS sensor. I guess the OEM ABS sensors are no longer available from Volvo :(

My car has passed her MOT for another year, so it's a sigh of relief. The ABS light has been coming on again intermittently, but miraculously stayed off during the MOT .... Phew!!! I thought the problem had been solved during December 2023, as she had both front ABS sensors, both the front wheel bearings and front reluctor rings replaced. My last scan with the 850 OBDII scanner pointed the issue to be the ABS module solder joints, but the indy's scanner said it was the n/s/f ABS sensor.

So, the next task is to re-solder the joints on the ABS module, as that is the only part that hasn't been looked into. I managed to remove the ABS module and open it up. The ABS module was rebuilt back in Jan 2023 and I can't really tell if the solder on the pins for the power and signal are cracked, dry etc. Now I'm in posession of a new soldering iron, I'm going to re-solder all the joints that cause the ABS/TRACS light to come on. For the solder joints/pins I've marked out in red, should the two be soldered together?

Yes, as you can see they are soldered together and this is correct. They are the main power feeds for the module (which feeds the pump) which therefore carry a lot of current, so they share two pins each to share the load.

All the best, let us know how you get on. :teeth_smile:

Hi Luxobarge, as always thanks for your replies with the useful information:). I'll be making a start on the soldering tomorrow. I've ordered a pot of flux too to help the solder, even though the solder I have already contains flux. I can't even remember what I last soldered or when and something I don't always do, so I'm just going to do it. This link (https://www.volvoforums.org.uk/showthread.php?t=72655) in the sticky by Jod T5 suggests re-soldering these pins in addition (see attached), so may do those too whilst I have the module open.

Yes, those are the pins from the multiplug connector, and are usually the main culprits - they were on mine, under a magnifying glass I could clearly see the cracks in the solder around several of the pins.

Any suggestions to clean excess flux off the PCB after soldering please? A video suggests using Isopropyl alcohol to clean off the flux. Will WD-40, GT85 do the same?

Many thanks in advance.

ABS module has been resoldered and was bolted back on this morning. Not done a test drive yet. Before I do the test drive, shall I clear any DTC errors codes stored in the ECU, start the engine and see what happens on the test drive?

Anything I've missed?

Yes, clear the codes. At least you will have a known starting point if any codes return. Good luck.

Thanks ITSv40, thought that'd be the case.

Before setting off on a test drive, I cleared the DTC codes via the 850 OBII app, did another scan and had the following output:

COMBI has 1 DTC: 02

CI-221: Vehicle speed signal missing [bad ABS module solders?]
[+ click to view more]

ABS has 4 DTC: 10 11 20 64

ABS-141: Brake Pedal Sensor, short [or bad ABS module solders, wiring, brake pedal sensor, or ignition switch]

ABS-311: Left Front Wheel Sensor, open/short? [or bad ABS module solders or ignition switch]

ABS-312: Right Front Wheel Sensor, open/short? [or bad ABS module solders or ignition switch]

ABS-321: Left Front Wheel Sensor, irregular > 25 mph (ie, interference or excess oscillation > 40 km/h) [or bad ABS module solders or ignition switch]
[+ click to view more]

At this point I wondered if my soldering had made things worse and when I accidently knocked the module off the bench I was soldering at :(, as I only ever had the top DTC error relating to the module.

During the drive of about an hour with speeds up to 70mph, the ABS/TRACS lights stayed on permently. The speedo was working fine at all times. At one point I stopped for petrol and hoped the lights would go out after turning off the engine. They didn't turn off. I continued driving for a while, then stopped to clear the DTC codes and do another scan. The second scan gave me the following output and only two errors this time:

ABS has 2 DTC: 20 30

ABS-312: Right Front Wheel Sensor, open/short? [or bad ABS module solders or ignition switch]

ABS-313: Left Rear Wheel Sensor, open/short? [or bad ABS module solders or ignition switch]

The right front ABS sensor is new, so wonder if my resoldering on the pins are not good enough. The left rear wheel sensor hasn't been replaced or is my resoldering on the pins for it not good enough again.

So, I'm thinking re-open the ABS module again and apply more solder to the specific pins bringing up the errors or just keep trying to clear the DTC codes. The 850 OBDII app is not the easiest to use and I'm not sure if I'm using it correctly. How can two scans give two separate results? On one scan, I can't remember in which sub-menu it was, but there were two ABS options to check, so I ticked both and did a scan (after I had done another clear DTC first). That scan said I had no DTC errors, but I still had the ABS/TRACS lights on. I then did a full scan by ticking all the available options, that's when I had the second lot of results above, with just the two errors. So the dreaded lights still haunt me :(

Between limited time yesterday, I cleared the DTC codes again and did a scan twice with the 850 OBDII app. And as expected, I had another set of different results to my previous scans. This time, the following same error came up twice, so there's some consistency at least.

ABS-312: Right Front Wheel Sensor, open/short? [or bad ABS module solders or ignition switch]

I didn't troubleshoot any of the issues relating to the other DTC codes I got on Saturday (as in the above post), so I was expecting them still to appear after another scan. Regarding the 850 ODBII app, would you folks say it's accurate and is telling me the correct output? I'm a bit dubious now as I've had different outputs from each scan.

Luxobarge ...... are you there? :teeth_smile:

Hiya,

Firstly, yes, the app is accurate so don't start doubting that.

Given the variety of codes, my first reaction is that it's still bad solder joints on those pins. I hate to cast doubt on your soldering skills but I'm struggling to believe that all those sensors or wiring are faulty, and I can't see what else it could be. This happened to me, the fist time I "soldered" it I failed to remove the clear jel coat covering the PCB, so my efforts at soldering had no effect. I still can't understand how I managed that, but the second time I had it apart I did it properly and never had a code since.

If you have another go, I can strongly recommend doing it under a large illuminated magnifying glass as I did - I borrowed the one my wife uses for sewing but if you don't have one try and beg or borrow one somehow. Using this, cracks in the solder that were invisible to the naked eye were clear to see, as was the end result after re-soldering. It also helps you to see if you've bridged any pins with solder which might be the case here. I'd not recommend using additional flux, it's not necessary and makes a right mess on the PCB, which might be hiding any solder that's got where it shouldn't.

HTH....

Thanks Luxobarge :regular_smile: I'll be removing the ABS module again to resolder the PINS that are relating to the DTC faults. Soldering is not something I've always done, so that could be the issue. I did make sure that any pins that weren't supposed to be bridged were not. I do have an illuminated magnifying glass. I'll get in there again with the soldering iron. The clear membrane on my module had been cut away before by whoever rebuilt it last. I'm determined to get rid of the lights and will keep going until I do.

When reinstating the module & the electrical connections double check that the plug is seated correctly and that the metal securing fixing on top of the plug is pushed fully over securing this plug.
(Worth doing a wiring check & clean whilst doing the above)

When I first purchased my car this fitting had not been fully engaged although it worked OK.
Good Luck.
Bob.

Hi Mr Meadows thanks for your reply. Which 'metal securing fixing' are you referring to? I don't even have the plastic cover on my plug connector, just secured with a zip tie (see the photo). I'm sure the wiring plug was seated properly by pressing down on it as far as it would go.

The wiring check - do you mean probe each connector on the wiring plug with a multimeter or just a visual check for frays etc? And lastly, is it OK to spray contact cleaner into the wiring plug (with the multi-coloured leads going into it) and the ABS pump power plug?

The plug would originally have had a big black plastic cover over the wiring and a metal lever that engages on the socket and pulls the plug tight down when it's flipped over. However yours are missing. Mine is the same, the lever assembly broke and departed some time ago, but so long as the socket is firmly plugged in all the way and held with a cable tie as you have done it should be fine.

Yes, it's fine to spray all the plug pins in contact cleaner, although I doubt this is the problem. While you're in there it's worth making sure that all the individual contacts in the plug are in the correct position and have not "sunk" down into the plug body. If this were the case then it's likely the "sunk" one(s) would be making bad contact, but a thorough visual inspection under a bright light will confirm one way or the other.

Hi Luxobarge, I'm not sure if I was clear as to which wiring plug I meant in my previous post, to spray with contact cleaner. In the first photo (ABS module socket), I've always been cleaning this one, but I was referring to the multi-coloured wire connector (red arrow in the second photo). Can I spray contact cleaner into this one ie the connecting block?

The answer's still yes, you can spray pretty much any connector with contact cleaner, but I doubt it will have any effect on your fault.

Thanks for clarifying that Luxobarge. Yes, I still need to resolder the joints/pins, so removed the ABS module again after work this evening ready for it.

I refreshed the following solder joints I did recently. No way is my soldering as neat as this.
Attachment 153506

And then tested the following pins on the module socket with a multimeter, as per the instructions on this link - https://midwest-abs.com/troubleshooting
Attachment 153509
LF sensor: pins 11 & 4
RF sensor: pins 18 & 3
LR sensor: pins 10 & 2
RR sensor: pins 17 & 1

I got a 'I' reading each time on the multimeter on the pins, when the multimeter is set to the 20K ohms setting. My soldering can't be good enough or I'm not using the correct soldering tip. The tip I'm using seems appropriate for the size of soldering I'm doing, so it must be my soldering :sad_smile: I don't think I've damaged the PCB. So, it continues.

Edit- no message

So, I removed the old soldering I did on the appropriate pins and resoldered with fresh solder. Looks a bit better than before and learning to solder as I go along.

I took some readings on the module itself on the speed sensor pins. My multimeter was set to 2000k on the ohms setting this time. I wasn't getting any reading when it was set to 20K (on the ohm setting again) and guess it is out of range. I hope that is correct. I got the following readings:

LF sensor: pins 11 & 4 = 142.5
RF sensor: pins 18 & 3 = no reading at all (need to resolder these pins)
LR sensor: pins 10 & 2 = 80.6
RR sensor: pins 17 & 1 = 80.5

Do I multiply these readings by one thousand to get the proper results? I'm only learning to use a multimeter as I go along and not sure how to interpret the readings. Can someone with more knowledge tell me if the values are what they should be please? I read somewhere the sensors should read between 800 - 1300 ohms.

Many thanks in advance.

Hi,

If these readings were taken with it plugged in on the car as intended, you've found the problem - wiring to the RF sensor.

Best regards,

Rich.

Hi richmac, I should have said that the ABS module wasn't connected to the car and the pins were tested on my work bench. I wanted to make sure I got a reading from the corresponding speed sensor pins on the module first before re-attaching back onto the ABS pump. And make sure the readings I have are correct.

My ABS/TRACS light issue had to take a back seat since the last update, but have resolved the issue now. I had the old ABS module I was trying to re-solder looked at by a colleague's friend who is a car electrician. They said the module was unrepairable, so I'm thinking I may have damaged it when I accidently knocked it off my work bench and damaged the PCB during my attempts at re-soldering. I managed to source another module of eBay, fitted it, cleared the DTC codes and no longer have the ABS/TRACS lights on.

Glad to have that ticked off. I hope this replacement module lasts until the next MOT by keeping the dreaded lights off. We shall see. Thanks for all the contributions from everyone on this thread.