OldnDecrepit
As some of you know i replaced my ABS module earlier this year with a repaired one from the US. After that the lights stayed off and for a few months all has been well.
Recently, I've been getting the ABS & TRACS lights coming on in my 1998 C70 under acceleration. Doesn't have to be hard especially when cold. I also had an overboost code come up recently but that was just the once.
After having some email discussion with a different ABS module repairer in the US, he has suggested that the problem might be the boost pressure switch rather than the ABS module.
Has anyone encountered this issue?
nickm
Or the pump motor wires. It is common for them to degrade. They are not in the ECU section.
Over boost could be the CBV or vacuum leak
ToomanyVolvos
There's a "quick and free fix" that can be found on the internet for a dodgy ABS unit - it sounds like the abs unit might not be the issue for you though.
Just for anyone else with the abs light issue I found a *fix* where someone wedged a piece of plastic alongside the abs unit and others replied saying it also worked. Believe it or not it worked for me:
Light was on 30% of the time prior and once the peg was pushed in just the right amount it's stayed off since. Must place just the right amount of pressure on the circuit board to resolve contact issues.
Ex850R
It's the connector shown above. One that is very hard to Unplug! So cleaning contacts is difficult.
Have you checked the wheel sensors? Wires and contacts in socket.
OldnDecrepit
I had cleaned the contacts & wires previous when I was trying to fix the problem before buying another ABS unit. It didn't work and I got a refurbished unit from a US source. All was well for months until this started. It is only occurs on acceleration - easy or hard.
I've got a new boost pressure switch on the way from FCPEuro. I'm hoping that will fix the problem. Another ABS unit won't be cheap.
ToomanyVolvos
If it's the ABS unit the peg actually works, it's at least worth a try.
nickm
nickm
My R threw a boost pressure code from a torn CBV.
OldnDecrepit
Well I replaced the boost control valve and the ABS & TRACS lights are still coming on on hard acceleration.
Other than a poorly repaired ABS module, I don't know what might be the problem. Other than the lights coming on the car seems fine and the lights are off next time I start the car.
My Bosch scanner does not detect the ABS unit, so maybe I've got a bad;y repaired ABS module.
nickm
There is silicone coating on the ABS circuit board. If you don't get it all off when you reflow the joints you can contaminate the new joints and end up with errors.
Others issues maybe your scanner will not talk to the ABS, have you tried something like VOLFCR.
I know generic OBD2 scanners don't talk to my 1996 one.
And have you checked the pump motor wires? and the ABS fuse?
OldnDecrepit
I can't speak for the ABS unit as I didn't refurbish it. The pump wires and fuse are OK.
My Bosch scanner doesn't see the ABS unit so I'm not sure if that's a problem with the scanner or the ABS unit.
I have been talking via email to a guy in the US that repairs these for a living (but didn't do mine) and he's doubtful it's the ABS unit. At this stage my money is on a poorly repaired ABS unit.
nickm
Grab a vag-com cable and use VOLFCR pm me if you need more info on that
So I gather the ABS does not work.
Can you solder? Any Electronic tech can reflow it easily. there are plenty of guides on line about this specific ABS unit.
OldnDecrepit
I have a cable already on its way and some software for my laptop.
If necessary, I still have the original unit from the car to do another exchange with a better source of repaired units.
Ex850R
Was it Midwest ABS?
OldnDecrepit
No, but they'll be the source of a new one if needed.
Ex850R
I recommend them highly, I ordered a scratched up reco one as we agreed sending one was cost prohibitive, but he sent me a nice looking one instead! Great service!
OldnDecrepit
Well I finally manged to read the codes from the ABS module and they are:
- 141 - EBD pressure switch signal, fault in circuit; and
- 142. - brake light switch, faulty signal.
If I understand this correctly it looks like the switch on the brake pedal is at fault not the ABS module?
Is this the switch at the master cylinder/booster or is there one inside the car?
Philia_Bear
OldnDecrepit;125152 wroteWell I finally manged to read the codes from the ABS module and they are:
- 141 - EBD pressure switch signal, fault in circuit; and
- 142. - brake light switch, faulty signal.
If I understand this correctly it looks like the switch on the brake pedal is at fault not the ABS module?
Is this the switch at the master cylinder/booster or is there one inside the car?
Faulty signal can easily mean bad solder joints
OldnDecrepit
The ABS module is a repaired one and this problem wasn't there after the replacement. It developed some time later so that makes me think that the refurbished module might be OK and the switch is faulty.
Philia_Bear
Or the refurb module was a bad module
Or you unplugged stuff while the car was not off
Clear codes and see if they come back instantly?