04' V70 ABS problems, how to troubleshoot?

Post by **850 LPT** » 15 Nov 2018, 11:27

The ABS/ anti skid warning light has been coming on intermittently starting 2 weeks ago. It usually turns off the next time I start driving, but comes on sometime later, with possibly a few days of no problems in between.

I stumbled across a FCP video where they are saying that the most common problem for this is a faulty steering angle sensor. Is that true?

Today a new symptom popped up. Hitting the brakes at slow speed resulted in a pulsating brake pedal and noise from the ABS pump. It sounded the same as when the ABS is kicking in on slippery surfaces.
Would this indicate a bad brake module? Or maybe a bad pump?

How should I attack this, this is new ground for me.

And is the car safe to drive? This pulsating thing is kind of freaking me out.

Thanks, Dirk

Post by **abscate** » 15 Nov 2018, 16:24

The wheel sensors are the things that give the most trouble - read off the codes and it might tell you what wheel to look over

Post by **oragex** » 16 Nov 2018, 05:42

Can't speak for the steering sensor, but start with the easy checks first. Abs reluctor rings tend to crack when the CV joint is rusted underneath and is pushing on the ring. A tiny crack in the ring will fool the abs sensor. See the ring at 1:30 www.youtube.com/watch?v=pxC9Ek9HhGI

The pulsating and noise thing is simply because the abs system thinks the wheel is locking (which is not) like when braking on ice, so something is simply triggering the abs. really nothing to 'worry', you may remove the abs fuse if it's annoying until fixed.

A wheel sensor can also go bad if the wire is stretched, you may try getting a used one for front and another one for rear from a junkyard - $5, just be careful to get them from a car that still has the whole suspension because the wires usually stretch when some suspension part is removed. To remove a sensor check here - never pull on the wire even just a little bit see at 9:55 www.youtube.com/watch?v=pxC9Ek9HhGI

Post by **abscate** » 16 Nov 2018, 06:58

I’ve forgotten if you have a good reader that can pull pending ABS

MaYbe I can catch at work on a NJ trip?

In CA at moment, back next week.

Post by **precopster** » 16 Nov 2018, 08:27

Though wheel sensor codes can be caused by a dirty ABS sensor or as Oragex suggested, a cracked ABS ring on the CV shaft I've never had a wheel sensor code go away just by cleaning the sensor which by the way is a very easy DIY job. The earlier ABS sensors (pre 1999) were highly magnetic and picked up metal shavings from the pad on disc friction. Later sensors have a plastic body coating and attract less debris.

The most common wheel sensor code is front left sensor and is due to a failing ABS module (also known as a BCM) The solder joints can be reflowed on the module to great effect. Sacer Industries supply new top covers for this MY so they can be effectively cut open with a dremmel and resealed. Any TV repair shop might take on the solder reflow job for a minimal fee.

After 2001 the module has been supplied by Volvo as a complete assembly with the ABS pump and hydraulic distribution block adding many hundreds of dollars to the cost of a new one as well as programming cost.

Post by **850 LPT** » 19 Nov 2018, 06:07

Seriously tardy on a reply here....

But thanks to all of you for the suggestions. Of course I didn't see the obvious and will try to clean the sensors as a first measure. Hopefully I will get to it over Thanksgiving break.

Beyond that if that doesn't work I think I'm going to need professional help (thanks abscate for your offer) as I'm not equipped with VIDA yet.

Dirk

Post by **abscate** » 19 Nov 2018, 10:13

Ive been getting a really rare (1-2x year) ABS power module fault error on the 2005 - it clears either by reader or by itself in 1-2 days at most.

Wheel sensor is still most likely - wait until you read codes to know which one to check

Post by **850 LPT** » 28 Dec 2018, 08:23

This was apparently caused by a loose axle nut on the passenger side

I guess when this happens the C/V joint can move around on the splines and the sensor gets confused by that.

I brought the car to my indie for a cat replacement and had him check this out.
Very cheap fix.

What's not going to be so cheap is the upcoming timing belt replacement and PCV replacement. He deemed the car worthy though so we'll go ahead with it.

Dirk

Post by **abscate** » 28 Dec 2018, 18:48

Totally forgot we fixed wcm XC70 ABS code with torquing the nut to spec, too,

That's a torque to yield bolt, so order a new one and keep it stashed. If it gets loose again, replace with new. Volvos says to replace whenever removed.

nickbw898 · Post by **nickbw898** » 19 Jul 2021, 10:28

Reluctor rings (tone rings) do go bad but I have only had this once in 20 years (and I do off-road). However, the ABS sensors themselves also fail and I have had both front sensors go in recent years. Vida fault tracing will confirm their failure. If you go to Diagnostics and select all four sensors, you can see how the wheel speeds are reported in real time. You can unplug them under the hood and use a multi meter in diode mode to test them.
I have seen video of ring replacement where the front suspension assembly was completely undone. This is unnecessary. Remove road wheel and undo the axel bolt (have a new one for reassembly). Release the sensor wire from its brackets. Jack both fronts and support with stands. Loosen bottom lower strut to knuckle bolt, undo top bolt. When this bolt is withdrawn the hub,disk/caliper will move forward enough to withdraw the CV joint splined shaft from the hub. To aid this turn the steering. While working on the ring support by strapping to coil spring. Torque for strut bolts is 105 N-m + 90 degrees. Torque for axel bolt is 35 N-m + 90 degrees. New bolts/nuts for all three advisable/