abs troubleshooting

Hi,

As some of you know I just finished replacing the rear springs and shocks on my

1992 900. This job required removal and reinstallation of the ABS rear wheel speed sensors. After I had everything put together, I drove around a bit, applying the brakes several times, with no problems. As I came to a stop, I felt the ABS pulse the brake pedal briefly, and then the "Anti-lock" warning light illuminated and stayed lit.

My first thought was that one or both of the wheel speed sensors was improperly installed or damaged. I inspected them, and they looked ok. Anti-lock warning light remained lit.

Next, I pulled the codes from the ABS computer using the protocol from the Townsend Imports web site. It gave me the following codes, in this order:

  1. 4444 - No fault
  2. 1241 - RF speed sensor
  3. 1243 - RR speed sensor
  4. 1311 - LR speed sensor
  5. 0000

If the computer were indicating a problem with the two rear speed sensors, that might make sense. But it is also indicating a problem with the right front speed sensor, which does not make sense-- I didn't even remove the right front wheel.

Any thoughts on what the next step would be to figure this out?

Thanks,

John

Reply to
John B
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I didn't get any bites on this thread today, and the problem continued to eat at me. In fact, I actually left my comfortably air conditioned place of work in mid-afternoon, went to the parking garage, and started flipping through the Bentley manual.

From the ABS wiring diagram, it looks like each wheel speed sensor can be tested from a 2-pin connector just after the wire enters the car. There should be resistance at something like 800 - 1400 ohms. My results: just over 1100 ohms at every wheel except the rear right, which had no continuity at all. So I took the road wheel off, took the wheel speed sensor out, and carefully inspected the wire. It looked like the outer insulation was a slightly cracked in a few places, but no major damage. After flexing the wire back and forth a few times, I read the resistance again- 1160 ohms.

Yay.

I put it all together, read all the codes from the computer again, and then drove the car > 20 mph, which should clear the codes. The warning light went off after I cycled the ignition. And so my auto mechanic skills advanced another notch.

I hope someone finds this story useful.

John

Reply to
John B

Salutations:

Most excellent post thx.

Reply to
Dexter J

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