1989 Ford Bronco ABS light dilema

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jimgad

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I bought my bronco about a month ago and thought I would have no issues for awhile. Previous owner took good care of it and did a lot of work on it himself over the years.
I am not overly skilled mechanically, but one thing I felt I could handle was changing all the dash and cluster lights bulbs to LED. Went fine and looks great. The day after my ABS light came on, and at first I thought maybe it was tied to LED's as those seem to cause other issues. For instance, I replaced my headlight bulbs and turn signal bulbs with LED. Headlights fine, blinkers fine when I did front. Once I put them in the rear blinkers stopped working, so I removed them. Doing a lot of google research I couldnt find anything that showed a correlation between the 2(LED and ABS light)

Finally took to a mechanic who has the correct OBD1 reader and was told I needed to replace the sensor on the rear differential. Once replaced, it went off, but came back on shortly after so I took it back.
The mechanic stated he would try to further diagnose. He thought there might be some metal flakes/shavings in the differential and that the sensor had a magnetic end, that they could be sticking too and causing issues. So he pulled it, and cleaned it to put back. HE told me if that cleared the light, then he would drain/refill the differential. He said when it was in the air, with engine running and in gear (tires moving at about 20mph) that the light went off. But when he hit the brake, it came on. He was behind at the shop and had my bronco for 4 days so he called me to come get it. He didnt charge me, but said he was at a loss as to what it could be. (never did drain/refill differential) When I drove it home, the light was on, but at one point it went off for a few seconds, then came back. Anyone else ever have a situation like this and can help lead me in the correct path? I do have an appointment next week at a Ford Dealership service spot, but not feeling overly enthusiastic.
 

Tiha

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It is not uncommon for the wires, twisted pair I believe, to rub through some where. Intermittently shorting out on the frame rail.

Worst case scenario the rear end does have metal flake and needs to be rebuilt. that happens as well but not nearly as often as rubbed wires.
 

miesk5

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Yo ya'll!
For Posterity:
Article No.
93-17-9​
  • BRAKES - REAR ANTI-LOCK BRAKE SYSTEM (RABS) - ADVERSE BRAKING CHARACTERISTICS - RABS WARNING LIGHT NOT ON, MAY OCCUR WHEN INCORRECT RABS MODULE IS INSTALLED - SERVICE TIP
  • BRAKES - REAR ANTI-LOCK BRAKE SYSTEM (RABS) - INCORRECT (RABS I) ELECTRONIC CONTROL UNIT INSTALLED IN RABS II EQUIPPED VEHICLES - SERVICE TIP
Publication Date: AUGUST 18, 1993

LIGHT TRUCK:1987-90 BRONCO II
1987-92 BRONCO
1987-93 F-150-350 SERIES
1989-93 RANGER
1990-93 AEROSTAR, ECONOLINE
1991-92 EXPLORER


This TSB article is being republished in its entirety to extend the F-Series application to include F-150 through F-350 Vehicles.

ISSUE:

Adverse braking characteristics and failure of the RABS light to indicate a RABS failure may be caused by improper servicing of RABS II equipped vehicles with RABS I electronic control units.

ACTION:

When replacing a RABS electronic control unit, refer to the following RABS Module Chart for correct parts usage.

RABS II modules have been designed with Keep Alive Memory and are to be used to service all prior year RABS I systems, except for 1987 and 1988 Bronco II vehicles.

MODEL YEAR​
VEHICLE LINE​
SERVICE PART NUMBER​
RABS MODULE (ECU) SERVICE CHART​
1987-91​
F-SRW​
F3PZ-2C018-A​
1992-93​
F-SRW​
F3PZ-2C018-C​
1987-91​
F-DRW​
F3PZ-2C018-B​
1992-93​
F-DRW​
F3PZ-2C018-D​
1987-91​
BRONCO​
F3PZ-2C018-A​
1992 ONLY​
BRONCO​
F3PZ-2C018-C​
1990-91​
E-SRW​
F3PZ-2C018-E​
1992-93​
E-SRW​
F3UZ-2C018-A​
1990-91​
E-DRW​
F3PZ-2C018-F​
1992-93​
E-DRW​
F3UZ-2C018-B​
1990-93​
AEROSTAR​
F29Z-2C018-A​
1989-93​
RANGER​
F29Z-2C018-A​
1991-92​
EXPLORER​
F29Z-2C018-A​
1987-88​
BRONCO II​
F3PZ-2C018-G​
1989-90​
BRONCO II​
F29Z-2C018-A​


SRW = SINGLE REAR WHEEL; DRW = DUAL REAR WHEEL




PART NUMBER​
PART NAME​
F3PZ-2C018-A​
RABS Module​
F3PZ-2C018-B​
RABS Module​
F3PZ-2C018-C​
RABS Module​
F3PZ-2C018-D​
RABS Module​
F3PZ-2C018-E​
RABS Module​
F3UZ-2C018-A​
RABS Module​
F3PZ-2C018-F​
RABS Module​
F3UZ-2C018-B​
RABS Module​
F29Z-2C018-A​
RABS Module​
F3PZ-2C018-G​
RABS Module​


OTHER APPLICABLE ARTICLES:​

NONE

SUPERSEDES:​

93-15-16

WARRANTY STATUS:​

INFORMATION ONLY

OASIS CODES:​

206000, 301000

You also may want to make sure that you don't have kinked metal brake line or collapsed rubber flex hose to the rear differential. You can crack the line loose on the RABS valve to the rear brakes and lightly press the brake pedal down and see if you get brake fluid from it then proceed down the line to the rear wheel cylinders doing the same thing. Checking the fluid.
 

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