2004 S60 ABS issues

[ringo98]

I have been struggling with an ABS issue on my 2004 S60 AWD for over a year now. Last winter (January 2018), I started getting ABS error codes. I took the car to a shop who read the codes and determined the BCM was bad. ABS error codes included:

BCM-0020: Right front wheel sensor, signal missing
BCM-E003: Configuration fault, faulty configuration
BCM-E000: Control module communication, faulty communication
BCM-0030: Left rear wheel sensor, signal missing
BCM-0010: Left front wheel sensor, signal missing

I sent the unit to Xemodex, and they repaired and returned the unit with BCM-0000: No DTC codes found. I put the BCM back in my car and I still had an intermittent code for the right front wheel sensor (BCM-0020, permanent fault). At that time, more often than not, the ABS light on the dash would come on in the morning, which was generally cold in VT, but not in the evening.

The same symptoms persisted but the ABS light was coming on more and more consistently and not just in the mornings, and now, it does not ever go off. The right front sensor code (BCM-0020) is always there (and does not clear) and sometimes there is a left front sensor code (BCM-0010), which does clear. Also though, in the past few months, the dash brake light and warning 'Brake failure, stop safely' is always on. This will clear with my code reader, but the code comes back when driving over 10 mph.

Given this experience, Xemodex sent out another BCM to rule out the unit. I put that new unit in my car, and I have the same results: constant right front sensor code, ABS light on the dash, and brake light and warning on the dash.

Here's what we've done and/or looked at:

- A year ago, the right front wheel sensor was replaced. No change in the error codes. (We actually had this sensor still around and the resistance was about 940-960 ohms, so this sensor may not have been bad.)

- The resistance of the right and left front wheel sensors, measured from the sensor connector, is about 940-960 ohms, which should indicate they are working.

- The resistance of the right and left front wheel sensors, measured from the BCM wiring harness, is the same 940 ohms. This suggests the wiring to the sensors is okay.

- The reluctor ring on the right front wheel sensor looks okay; slight rust (similar to the left reluctor ring) but no cracks or severely deformed teeth. We actually replaced the left ring (which was interesting), and we could replace the right ring I suppose. Given that the right front code will not clear at all, even when the car is sitting still, I have doubts it's the reluctor ring.

- The right front wheel bearing was replaced about 2 years ago. I've heard a bad wheel bearing can cause wheel sensor issues, so I suspect this relatively recent replacement would rule this out.

- Other possibly related things: The odometer and trip meter will not work when the brake light and warning are on (I'm not sure if this is how it's supposed to work). Also, the temperature display on the dash is more often wildly off than correct.

I'm really not sure what to go for next, as we've attempted to rule out what the ABS error codes are indicating. Also, I'm unsure whether the constant/unclearable ABS code will trigger the brake light and warning, or if that is the result of something else.

Any help is appreciated.

[abscate]

Did you use a new bolt when you replaced the hub? That bolt is a single use and has to be torqued correctly or you will get ABS codes.

The ABS self tests at 10 mph on each drive cycle so that behavior probably means your BCM is good but is finding bad signals as indicated

[ringo98]

Been a while since I last posted as I've been juggling some things and spending too much time on this without resolution.

Did you use a new bolt when you replaced the hub? That bolt is a single use and has to be torqued correctly or you will get ABS codes.

The ABS self tests at 10 mph on each drive cycle so that behavior probably means your BCM is good but is finding bad signals as indicated

I checked with the mechanic that did it and yep, a new bolt was used. Can you elaborate on 'bad signals', especially suspect areas if there are any?

Since my last post, I'm still struggling with this. I have had both front reluctor rings replaced with Volvo parts, I've had a Volvo BCM put in to rule that out, and I've had the front right wheel sensor replaced (both left and right check out with resistance tests, but right was replaced anyway). Taking some tips from some other posts, I cleaned the contacts of the ECM with Deoxit, but that didn't have an effect. I had a thought to take a look at the junction block between the CEM and the BCM (located just forward of the CEM), but that's impossible to get to without removing the dash.

I currently still have front left and right wheel sensor codes (BCM-0010 and BCM-0020, respectively), and an occasional BCM low voltage code (BCM-0057). The low voltage code will clear, but the wheel sensor codes will not. As before, the red dash brake light is constantly on and will not clear as well.

All thoughts are appreciated.

[537playing]

I feel your frustrations. I had the ABS light on and ended up using a donor part to replace just the ABS motor. That solved my problem. Could this be your issue? It’s just a guess.

[ringo98]

I feel your frustrations. I had the ABS light on and ended up using a donor part to replace just the ABS motor. That solved my problem. Could this be your issue? It’s just a guess.

Do you mean the ABS pump? What were your symptoms?

[537playing]

Yeah. That pump. I only had the light come on. It never handled well on wet surfaces.

[ringo98]

Yeah. That pump. I only had the light come on. It never handled well on wet surfaces.

Ah ok....I'll keep this in mind.

[conkerkh]

I have exact same problem on my Car, although codes cleared out last time but the error comes back at some point every now and then. I started same replacing BCM, this resulted in no codes however BCM wouldn't calibrate fully... I also noticed that I would lose brakes under hard braking and ABS would kick in for no reason, mechanics diagnosed faulty ABS pump motor - replaced it. After replacement ABS was working fine but again every now and then I get errors on front sensors (just like with previous module). I'm almost 100% sure BCM is fine since it's not really possible that two of them are wrong and exactly the same codes come up. I was driving for some time with bad bearing at the front it was replaced with new hub I believe they used new bolt (I hope). This really seems to some kind of mechanical issue on the car, which makes the ABS sensor readings freak out. From what I'm aware ABS sensor on this Volvo has 2 wires and is PWM based so it makes ground connection with it's body (correct me if I'm wrong) so only thing that comes to my mind is: no proper ground connection on the sesnsor itself, still some problem with the bearing, some other electrical noise, I'm driving like this for over 2y and it's also driving me mad.

[ringo98]

Update here:

We were starting to question whether the alternator was doing something odd. We hooked up an oscilloscope to look at the AC waveforms on my S60 (the car with the ABS issue) and on an older 850. The waveforms were certainly different. The 850 had a lower amplitude and 'normal' looking signal, based on what I can find online. My S60 had a larger amplitude signal (maybe 0.4-0.5 V) and also an underlying and low frequency sinusoidal wave (amplitude of maybe 0.3 V).

We ended up putting the battery from the 850 into the S60 as an initial step just to check to see if the battery had an effect. It did have an effect. (Somewhere in the middle of all of this I cleaned the ABS sensor connectors and the brake booster connector with Deoxit.) The brake dash light was not on upon starting the car, and this was the first time in a very long time that I could clear all of the ABS codes. However, this did not last, and the right front ABS code came on later, as well as the brake dash light. (I suspect that if both the front ABS sensors throw codes, the brake dash light illuminates. I'm not totally certain about this, but that's the correlation I'm seeing when checking the codes. This is annoying if the problem is in fact limited to the ABS system.) Also, sometimes I am still not able to clear the right front ABS sensor code. Furthermore, when I can clear all of the codes, the right front sensor code may come back randomly when the car is in park and there are no other changes happening in the car (no additional electrical loads, etc.).

Prior to taking the alternator out, we decided to see if simply disconnecting the alternator cable had any effect on the ABS codes. Removing the cable from the alternator was really not too bad. Removing the hose going of the top of the engine was necessary, but that allows for two-finger access to the cable and nut on the alternator, and to be able to insulate and tie up the loose alternator cable (I used a small plastic bottle and zip-tie). I drove the car for about a mile and the ABS code for the right front sensor remained, with the same issue that it randomly does or does not clear. With the alternator still disconnected, we also looked at the AC waveform on the car. While it was different than when the alternator was connected, it still didn't look 'normal' (large drop-off at the end of each wave). Seeing this, we are guessing the alternator does not have an effect on our issues, and we put the alternator cable back on.

Another individual mentioned that the DIM can cause random issues sometimes. I might see if I can my hands on a cheap one that fits my year/model. Still on the hunt ...

[conkerkh]

Any news on your problems? Did you manage to further track down what could be an issue?