ABS Rear Wheel Signal

psflyr · Post by **psflyr** » 10 Nov 2009, 12:37

I took my 2001 XC70 to the shop for an intermittent right high beam headlight.
They found a loose pin at the control module under the dash. When I got in the car after the fix I had an "ABS Brake Service Required" message. Never had it before they touched the car.
Back on the computer it went. The following codes popped up:

BCM-0074 HYD Valves Faulty Signal
ABS-0030 Left rear wheel sensor Signal missing
ABS-0031 Left rear wheel sensor. Faulty signal

Being a glass half empty kinda guy when it involves cars, I am left to wonder if they did something while working the headlight issue that caused this ABS problem, i.e. power issue at the control module that perhaps 'spiked' the BCM?
They want to start with a rear sensor change and see if that fixes the light. After that I suspect the valve and then finally the BCM.
Thanks,

Japedo · Post by **Japedo** » 10 Nov 2009, 12:50

Could be just an unplugged sensor, i'd say your issue is localised to that left rear wheel. Be it a bad sensor or a damaged wire to it. I doubt it's your brake controll module, but possible.
BUt if you can change a tire on the side of the road you can likely replace that sensor yourself and let the dealer screw the next guy.
Im a glass half full guy when it comes to dealers.....

Good luck

psflyr · Post by **psflyr** » 10 Nov 2009, 13:15

LOL......yes i can replace a tire. Trying to locate directions (here) for replacing the sensor. Where do I look for help (instructions).
Thanks

Japedo · Post by **Japedo** » 10 Nov 2009, 13:26

I haven't looked for any directions, but with the tire off it should be the only thing on your rear brake assembly that has a wire going to it, and there is an electrical connection at the sensor, so unplug that and im guessing the sencor itself should be held in by one small bolt.
This is my guess, ive never replaced one on my XC. Im gonna take a look around here and see if I can find u some clearer instructions.

Welcome to the forum by the way!

curtis

psflyr · Post by **psflyr** » 10 Nov 2009, 13:40

Curtis,
Thanks for the help and info !!
Will be nice to save some money for a change with this car!
It's getting a bit 'long in the tooth' as they say and the 'few' dollars here and there for minor fixes are starting to add up.
I'll look for your post.
Cheers,
Paul

Post by **JRL** » 10 Nov 2009, 15:48

Slow down

it ALWAYS says L/R sensor, your sensor is most probably just fine.
96-01 ABS modules always need replacing at one time or another, just get it rebuilt, it will never go bad again.

www.modulemaster.com
Their prices have been reduced to $100!
Or if you just want to sopend money a new one from Volvo will cost 8-$900!

psflyr · Post by **psflyr** » 10 Nov 2009, 19:38

The shop checked the signal from the wheel sensor and said that there wasn't anything being transmitted. This confirmed the diagnostic code. Now, from what I have read here, and on other sites, there can be a number of reasons for this ranging from complete failure to dirt. So I have to wonder if their diagnosis isn't correct. Having said that, if I take your advice and get a new module from the website you've mentioned and it turns out NOT to be the cause, can I return it? Or, will you pay for it......

?
Cheers,

Post by **polskamafia mjl** » 10 Nov 2009, 19:49

Haha, that's the spirit. It is true the ABS modules do fail. You should however clean the sensor first and see if that changes anything.

Japedo · Post by **Japedo** » 10 Nov 2009, 20:48

Absoulutley, It doesn't cost money to check the simple things first. Connections, wires, the sensor itself.
And if you want to look at it like JRL posted above "they all need replaced eventually" that is also true for the car itself.
That being said I understand that he has alot more experience than me or maybe anyone on this forum, so he's likely right.
But again troubleshooting to be sure is cheap.

curtis

psflyr · Post by **psflyr** » 13 Nov 2009, 09:54

Today I had the left rear wheel sensor replaced. Both the faulty and missing signal codes are now gone. However, the ABS Hyd Valve (faulty signal) is still present. Will probably have to replace the ABS module at this point.
Does anyone know the connect the dots view for the ABS module?
By this I mean what is its power source. A FWD control computer (module)? What else ties into this computer? Do headlights, wipers, etc... also tie into this power/control source that the ABS module uses?
Thanks,
Paul