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More ABS / brake weirdness V70-XC70 2004

posted by  riverbend on  Tue Jun 3 21:26 CST 2014
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last visit: Wed Oct 22 15:29 CST 2014
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Long history of seemingly ABS related troubles. recently Mary was cruising down a hill to a stop (on dry roads) and found that the brakes did not appear to work. 'It wasn't the little zzt, zzt, zzt like the ABS was working it was bigger, Uhh, Uhh, Uhh, like tightening a belt.' Anyway, she got the car stopped, but was unhappy with the brake performance. The ABS light had been on for some time previous to this.

While I was changing the oil I checked each of the wheel sensor and came up with between 15 and 25 ohms each on my analog meter. The ABS light was on upon start up, but went out at about 15 MPH.

Today Mary drives the car and she notes:
(ABS) Light off after you messed w/ sensors. All OK for a while ( a day). The light came on. Ran and braked okay for a mile. Stopped for 1 hour. Got in and ABS light out. And 2nd stop sign, brakes were bad (not stopping the car). Left stop sign and tach went up and car wouldn't shift. The ABS light came back on and it shifted. Brakes now OK again. There is a ticking noise, seems to come from wheels, can't tell front or back.

The connector to the ABS modulator is very clean and latches tight. Has anyone seen ABS module failures on the P2 cars like what showed up in the late '90s cars ? Anyone had a P2 modulator apart and looked at the circuit board ?

Ideas ? Mary won't drive the car anymore. It may be time to see the dealer for a scam er scan.

Greg







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    More ABS / brake weirdness V70-XC70 2004

    posted by  mopar2ya on  Sun Jun 8 19:29 CST 2014
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    last visit: Mon Jul 7 07:35 CST 2014
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    if you remove the abs module your brakes will be normal without abs, however it sounds like a brake booster vacuum problem, I had this trouble with my xc, at slow speeds the brakes would stop the car, at 65 mph you better hang on. my trouble was the o ring on the pedal sensor on the brake booster. replaced the o ring and brakes are fine, with that said, one of your wheel sensors is bad,you said it would not shift, mine was the left front sensor, hope this helps,
    --
    2001 v70 T5, 2001v70XC, 2002 XC70, 2004 XC70, 1988 740 turbo wagon








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    More ABS / brake weirdness V70-XC70 2004

    posted by  KlausC on  Wed Jun 4 14:56 CST 2014
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    last visit: Fri Oct 24 10:15 CST 2014
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    ALL of the communication goes through the CEM. A fault in the CEM could be your problem. A proper scan tool is needed for that. But, I suggest you drive the car to Borton - I wouldn't want to see Mary get hurt!!!

    www.xemodex.com has rebuilt CEMs, if that is the problem. Beats the heck out of the dealer prices.

    Klaus
    --
    My back feels better when I sit in a Volvo seat








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      More ABS / brake weirdness V70-XC70 2004

      posted by  riverbend on  Thu Jun 5 06:37 CST 2014
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      last visit: Wed Oct 22 15:29 CST 2014
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      Thanks Klaus, your concern for Mary's safety is touching.

      After reading a little on a few other websites, it sounds like even the dealer has a hard time telling what exactly is wrong when these systems go haywire. Shotgunning in a few $500 (XeMODeX)parts to see what works is not a very satisfying way to troubleshoot a problem.

      I have been driving the car a little and the ABS light is very intermittent. On start up the light can be on or off. It may or may not come on while driving. The only consistent thing is that the ABS light will come on after hitting a bump. I have not experienced the big ABS intervention on dry roads. The roads being what they are, it is a weak correlation at best.

      In any case, the light may or may not be on by the time I get to Borton's shop. And once they start the car, it may or may not be on.

      Greg







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        More ABS / brake weirdness V70-XC70 2004

        posted by  Volvony on  Sat Jun 7 13:32 CST 2014
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        last visit: Sun Jul 6 08:57 CST 2014
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        I had a problem like this (2000 V 70 ) that turned out to be a cracked circuit board in the ABS module, the black box under the block of metal that distributes the brake lines. I sent it to someone in L.A named Victor Rocha who rebuilds and repairs them for $125 and three years later, my ex has no complaints about the ABS. ABS modules are capable of randomly turning on and off the speedometer,( the odometer is not affected but the other gauges are ) of ordering the car into "limp home" mode, and of affecting brake performance








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          May have found the problem V70-XC70 2004

          posted by  riverbend on  Sat Jun 14 18:15 CST 2014
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          last visit: Wed Oct 22 15:29 CST 2014
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          Today I decided to clean all the ABS sensors, check for cracked encoder rings, loose hubs, etc. The front left sensor was loose. When I replaced it this winter it appears that a drop of mud fell into the bolt hole and kept the bolt from fully seating.

          That would explain why the ABS light would come on when hitting a bump. If the car behaves itself for a couple weeks, I'm tempted to declare it fixed.

          Greg






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