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  1. #1
    Join Date
    Feb 2017
    Posts
    123

    Default ABS light is on, code is ABS circuit A, replaced pedal position sensor, still on

    The title sorta sums this one up. I have the 'pull over safely urgent' issue message, ABS lights on. Code is 'brake circuit A' and sometimes 'brake circuit A and B'. Googling suggested the brake position sensor which I replaced today. I cleared the codes, but it came back up.

    This issue is intermittent, pretty much 50/50 and once you start the car if it's off it stays off and vice-versa. I have a Volvo specific code reader and I cleared the codes with that, still came back. I had also replaced both front ABS wheel speed sensors out of an abundance of caution.

    Also replaced the brake light switch sorta by accident.

    What else could it be?

    This is my 2002 V70 XC turbo inline 5.

    drGian
    current lineup: 2001 Volvo v70 2.4 Turbo, 2014 Ford Flex AWD, 3.5 V6 Turbo, 2017 F-150 3.5 V6 Turbo

  2. #2
    Join Date
    Feb 2013
    Location
    Boston, MA
    Posts
    1,196

    Default

    What codes did you have? Read by DiCE/VIDA if possible.
    2002 V70 (sold)
    2005 XC70 (Telos Road took it. Did a chassis swap)
    2016 XC60 (sold, P.O.S.)

  3. #3
    Join Date
    Feb 2010
    Location
    Virginia Beach
    Posts
    4,116

    Default

    Googling suggested that I have terminal cancer.

    But a couple of Tums cured my symptoms, so...

    Look, you really need to do some more troubleshooting, which must include testing, on this. A code doesn’t mean that a particular component has failed, only that the car has registered a fault. Another component may be causing this problem.

    In your case, the ABS module is a weak spot, so are the reluctor rings themselves. A bad reluctor ring will show up as a wheel sensor fault since the wheel sensor isn’t reading speed properly.

    So, cheapest thing to do is examine each ring closely, clean them up and look for cracks. Go from there.

    A Volvo-specific code reader is nice, but only gets you about 10% of the way through the troubleshooting process. The additional steps in VIDA will walk you through the rest.

    But examine the rings first. Maybe you’ll get lucky. Throwing parts at it is going to get expensive.
    Current Fleet:
    2016 Tundra Crewmax 4WD 1794
    2005 MB S600 (126K, Michelin AS4, HPL 0W40)
    2005 MB SL600 (55K Michelin AS4, Mobil 1 0W40)
    2004 V70R (143K, six speed M66, HPL 5W40)
    2004 XC90 (235K, HPL 0W30 Euro)
    2002 V70-XC (295K, HPL 0W30 Euro)
    2002 V70-T5 (225K, IPD bars, Bilsteins)
    2001 V70-T5 (125K, IPD downpipe, cat back and other mods)
    1932 Packard Sedan (straight 8, dual sidemounts, original paint and interior, Shell Rotella 15W40)

  4. #4
    Join Date
    Feb 2017
    Posts
    123

    Default

    are the reluctor rings the gear looking like rings that the wheel speed sensors are pointed at? I assume I can get at them just by pulling the wheels off. I will do that and look for cracks and let you know what I find after they are cleaned up.

    I have a bootlegged copy of Vida but it has expired, I think there is a really easy way around that I have research what it is, but first I'm just going to try setting the date back a few years to when it last worked.

    Thanks, I'll keep you posted.

    drGian
    current lineup: 2001 Volvo v70 2.4 Turbo, 2014 Ford Flex AWD, 3.5 V6 Turbo, 2017 F-150 3.5 V6 Turbo

  5. #5
    Join Date
    Feb 2017
    Posts
    123

    Default

    Hello all,

    I finally got a chance to check the reluctor rings, at least the front ones. I didn't see any cracks, but they were filthy with grease and debris and small bits of rust that had flaked off of the rotor air flow gadget that directs air flow over the rotors. I cleaned them up really nice with some PBS blaster and a wire toothbrush and hit them with some compressed and they looked brand new.

    Started up the car and attached my code reader with has 2 modes, normal ODBC and volvo specific codes. There are a few ABS errors (I have attached pics of all the codes I'm gettting now). the odd thing was after I cleaned the rings, the ABS warning lights went off just by my reading the codes, not resetting them. So I figured, problem solved and gave the car back to my daughter.

    A few days later she reported that the ' brake failure: pull over immediately' light was back on and while I can't say I was surprised, it didn't make my day. So today I went back in to see what I could have missed, I was also hearing noise coming from the front right wheel that sounded like that piece that directs the air flow over the rotor scraping something.

    so front driver: sure enough, I had bent that thing and it was scratching the rotor. As I fixed that I noticed that I had neglected to tighten the center bold that pulls the end of the transaxle into the wheel hub, it's a 10mm. When I did, it moved forward about 1/2 inch so I figured maybe that was it, maybe with that ring out of position the sensor couldn't read the ring. I checked the passenger side as well and all looked fine there.

    So here's the interesting part, now when I read the codes, ABS light and warnings stay on, when I reset the codes, they also stay on so I'm kind of at a loss what to do next. I will post the errors I'm getting and I will do the same procedure to the rear wheels (tightening the center bolt this time) and report back. This is weird, because when I did the first cleaning, the ABS errors all resolved just by my reading the codes. I have a autophix vol-vo reader, I don't have it in front of me, but it's server me well so far.

    In the meantime any input is appreciated as always.

    I have an unrelated air bag issue that I introduced strangely enough when I swapped the rear seats with a 2001 (this is a 2002); the belts won't unwind regardless of speed or any variable. But I'll deal with when I'm resolved the
    ABS issue, unless they are somehow related.

    Thanks for any feedback. Any new codes that show up, I will post here as a reply. There are some I have seen (like communication with ECM) that seem to have resolved after a pulled both ECU's, cleaned the pins and sprayed them with eletroconductive stuff.

    drGianClick image for larger version. 

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    Last edited by drgian; 08-08-2020 at 02:27 PM.
    current lineup: 2001 Volvo v70 2.4 Turbo, 2014 Ford Flex AWD, 3.5 V6 Turbo, 2017 F-150 3.5 V6 Turbo

  6. #6
    Join Date
    Aug 2017
    Location
    Pleasanton CA USA
    Posts
    486

    Default

    What about the rear wheel sensors? The benefit of using VIDA for an ABS fault is that it will report out which specific wheel is reporting in a mismatched speed to the other 3. Then, you know where to focus your efforts. Also, with VIDA, you'll be able to reset the SRS fault that was thrown when the rear seat electronics were unplugged.
    2013 XC70 T6 Flamenco Red (hers)
    2015 XC70 T6 Seashell Metallic (his)
    past: 13 Volvos going back to '74 242 sedan

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