Curt Posted January 22, 2006 Share Posted January 22, 2006 Having a little problem with what may be the ABS on the rear wheel of my '97 RT. Symptoms : 1. Alternating ABS fault light. Might be a low battery. 2. Rear wheel lockup when applying the rear brake at anything ove 10 mph. "Feels" like ABS pulses, followed by lockup and wheel slide to the right. I checked the air gap on the rear sensor and found it to be too tight, so shimmed to withing tolerances (0.5 - 0.55 mm). Checked brake pads and caliper tightness. Cleaned the end of the rear ABS sensor. Still does it.... Any ideas on what might be causing this problem or how to diagnose faults in the ABS system (if that's what it is...)? Thanks Link to comment
Joe Frickin' Friday Posted January 23, 2006 Share Posted January 23, 2006 Having a little problem with what may be the ABS on the rear wheel of my '97 RT. Symptoms : 1. Alternating ABS fault light. Might be a low battery. 2. Rear wheel lockup when applying the rear brake at anything ove 10 mph. "Feels" like ABS pulses, followed by lockup and wheel slide to the right. I checked the air gap on the rear sensor and found it to be too tight, so shimmed to withing tolerances (0.5 - 0.55 mm). Checked brake pads and caliper tightness. Cleaned the end of the rear ABS sensor. Still does it.... Any ideas on what might be causing this problem or how to diagnose faults in the ABS system (if that's what it is...)? Thanks If the ABS lights still alt-flash after cycling the key, then it's not a low-voltage fault (unless your battery is so flat that it can't even maintain good voltage before thumbing the starter). go here, and go to page 71-72 to see how to read the ABS fault codes. Likely you've got a sensor problem. Link to comment
Green RT Posted January 23, 2006 Share Posted January 23, 2006 You didn't mention resetting the ABS. I assume you did a hard reset of the ABS (Ground middle pin on diagnostic connector and hold abs switch for 8 seconds)? Link to comment
Green RT Posted January 23, 2006 Share Posted January 23, 2006 Another thought. My understanding of ABS is that when there is a fault and the ABS light is flashing, the ABS is completely disengaged. You say the ABS pulses. I assume you mean the brake lever pulses. Is it possible you have a warped rotor. This would vary the clearance on the ABS sensor and might cause a repeating ABS fault. Link to comment
Curt Posted January 23, 2006 Author Share Posted January 23, 2006 Thanks. I'll run a diagnostic on the ABS system >Likely you've got a sensor problem.< Anyone know if there's a way to check continuity on the ABS sensor? Looks like a sealed unit to me, but if anyone has any ideas........... Thanks. Link to comment
Green RT Posted January 23, 2006 Share Posted January 23, 2006 Upon further thought. A warped rotor wouldn't affect the sensor. But it could explain the pulsing. Link to comment
Joe Frickin' Friday Posted January 23, 2006 Share Posted January 23, 2006 Anyone know if there's a way to check continuity on the ABS sensor? Looks like a sealed unit to me, but if anyone has any ideas........... AFAIK it's just a coil that inductively senses the wheel teeth (a VR sensor), which means you'd be looking for some small resistance value (i.e. something other than open-circuit). However, that's no guarantee; in '03 I had a problem with my RT where the ABS computer insisted there was a problem with the rear sensor, but I couldn't find anything wrong with it. I replaced it, and everything was fine. Let's see what your ABS computer says first. Link to comment
bmwmick Posted January 23, 2006 Share Posted January 23, 2006 Thanks. I'll run a diagnostic on the ABS system >Likely you've got a sensor problem.< Anyone know if there's a way to check continuity on the ABS sensor? Looks like a sealed unit to me, but if anyone has any ideas........... Thanks. Put an Ohmmeter on the sensor wires with it disconnected from the harness. You should see around 135 Ohms. It's nothing but a coil of wire like Mitch said. Better yet, read the stored fault codes before you reset and let us know what fault you have. Mick Link to comment
Curt Posted January 24, 2006 Author Share Posted January 24, 2006 >Let's see what your ABS computer says first.< Well, howdy-doody. I did the ABS diagnostic and guess what? No ABS faults (once I let the battery get back to a normal charge level to get rid of the low battery fault). I'm mystified. No faults whatsoever showing, just the normal codes saying eveything is O.K....... I'm going to double check the sensor gaps and replace the rear pads. Anyone have any other ideas? Link to comment
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