Brake warning lights and Abs

[Tomcat]

For a while now I've hat intermitant ABS warning lights on, I swapped out the abs ecu for another that was apparently ok and the lights now come and go less often (yet they're still on a lot).This morning the Red brake warning light has started coming on, it seems to go off if I'm braking but while driving its on all the time. I've checked the brake fluid and there's plenty of that.. What else would cause it to come on?

[jamesy12345]

Master cylinder ever been changed?? Pads OK?

edit

does your car work with VOL-FCR, TC? Might be one of the wheel sensors or wiring to them if you are still getting ABS light also

[Tomcat]

Rear pads are brand new front pads had loads of material on them last time I checked. As far as I know the master cylinder hasnt been changed. It brakes fine but occasionaly when the abs lights arent on you get a strong vibration through the brake pedal, it'll last a couple of minutes and then suddenly it stops and the abs/tracs lights come back on. I'm thinking of taking it the local indy and just paying them to read the codes for me, sick of second guessing now.

[merc85]

Brake wear indicators buddy, (worth a look anyway)

[Tomcat]

I'll check the front pads tomorrow, I know I was doing some serious breaking the other day so maybe it is that. Cheers...I'll stop panicking now...

While we're talking about it, what's likely to be causing this bloody ABS/TRACS light to keep coming on?.. Would a dodgy abs sensor cause it?

[merc85]

Usually dry solder joints as you have said, But a Cracked abs Ring, would also do it, and a Faulty sensor, or even debris on the sensor itself.

[jamesy12345]

I was a bit slow there editing my post

Maybe try VOL-FCR if it works with your car?

[Wobbly Dave]

Reluctor rings. Check for cracks, missing teeth, dirt or damage.

[Tomcat]

Right I've taken it to the local indy this morning, thankfully it didnt cost me too much as I know them really well. It turns out that the red warning light was on (here's where I've been stupid) because the brake fluid was actually quite low. In my defence when I checked it I only pulled the cap off and there seemed to be loads in it, but I didnt really look at the level. Apparently there's a pressure switch on the master cylinder and that's leaking, not sure how as I've never noticed it before. The ABS/TRACS lights are on and off, apparently the codes coming up are for both rear sensors (as they're linked), he said he cleared the codes and they came straight back. He thinks the right rear siensor is the problem.

[Tomcat]

OK... Both rear sensors have been replaced along with the leaky pressure switch, sadly the lights are still intermitant.

[jamesy12345]

Did you run the diagnostics again, TC? If it is still saying the sensors have failed, maybe there is a way to check wiring to them...just a thought

edit

I've used this company before, pretty good

https://www.midwest-abs.com/Troubleshooting.php

[Tomcat]

It's booked in at the indy on Friday for a re run of the diagnostics, hoping it's something simple as I'm getting fed up of fixing stuff that doesnt end up being fixed. Thanks for the link James.

[partsforvolvos.com]

Brake wear indicators buddy, (worth a look anyway)

there aren't any on Volvos, unless its an ex-police or emergency services car.

[MIXA]

Just had the same symtoms on mine , my brake ecu had to be repaired also the front offside ring was cracked which had some how damaged the sensor as well had the ecu repaired by Kent volvo spares , bought a complete u/j still to be fitted and a new sensor fingers crossed it cures it

[jamesy12345]

Any news TC?

[Tomcat]

Nope, not yet. System is getting more stable ie.. The lights are intermitant for longer periods now.

[jamesy12345]

Nope, not yet. System is getting more stable ie.. The lights are intermitant for longer periods now.

OK fella, good luck finding it

in that link above there is a little write up about finding any breaks in the sensor wiring

To test the ABS wiring (from the sensors to the module) for an open circuit, put a multimeter on the following pins on the ABS module connector (not the module itself) . They should test out between 900-1380 ohms

This only works for 1996-1998 models, not the 1999 and later cars. On 99-2001 cars you can only test the sensor itself, not the continuity of the circuit.

LF sensor: pins 11 & 4
RF sensor: pins 18 & 3
LR sensor: pins 10 & 2
RR sensor: pins 17 & 1

I just mention that cos it seems like you have replaced a few different parts without sorting it, must be frustrating

[Tomcat]

Yeah it's driving me up the wall bud, that's a great way to test them though, thanks for that, I'll try and test them today.

[Tomcat]

Right.. Yesterday I finally got around to checking the wiring on the ABS, I took the connection off the ecu and the readings for the rear sensors where roughley 1180ohms so no faults there. The odd thing is, since checking it and reconnecting it the lights haven't come back on... I've been out 3 or four times now and it would normaly have shown itself by now but so far... nada.. I'm off on a long drive tomorrow (approx hour and a half each way) so that'll be more of a test but so far it's looking good.