Problem with Rear antilock system on 89 Ranger

[cgrey8]

In the past when I'd get the Rear Antilock Brake light on and staying on, it was the ABS Hydraulic unit mounted on the frame. I've had to replace it a few times now. It'd get to where the pulsing components in it just wouldn't pulse anymore. And every time I replace it, I hear the pulsing noises of the initial key-ON ABS testing revitalized and working. However after replacing the ABS unit this time, I didn't hear those pulses return on key-ON and my ABS light is still coming ON after about 2 minutes of driving just like before I replaced it. If it's not the hydraulic unit, what else could cause ABS issues that would illuminate that Rear ABS light on my dash after a few minutes of driving?

[Grumpy]

check the magnetic sensor that is mounted into the top of the rear end housing.. my 90 was doin the same thinng and Ford told me to replace that sensor........... it worked for like a year or so ... then the light came back on .... i never replaced it again....lol
i dunno if that will cure yours tho... the sensor isnt that expensive either ....i got mine at Advance Auto Parts ....

[cgrey8]

I know that sensor you are talking about, however I have no clue what that sensor is called to look it up on AutoZone's website. Any idea what that sensor's name is?

Edit:
It seems AutoZone doesn't think my truck has one of those sensors, although it knows I have an ABS Hydraulic Unit and ABS module (computer). I had to enter a 1990 Ranger to find it. And yeah, it's only $15. So that's an easy thing to try to see if this fixes the problem.

[cgrey8]

Well, I've been ignoring the Rear ABS light for the past few months, but I eventually need to get this back working. I've replaced the ABS valve that's in the brake line on the frame rail and I've replaced the rearend sensor as recommended above. Neither of these fixed the problem. In addition, I notice that the ABS valves no longer cycle when I turn the key ON. When it was working, I remember hearing the ABS system pulse those valves. It was an audible noise as those valves got pulsed.

When I've had the ABS valve go bad, I'd hear the intensity of those pulses weaken to the point that it was a dull click that was barely audible. Eventually it'd quit altogether and the ABS light would come ON. After replacing the valve, the pulsing would return to normal on KOEO.

Earlier this year, I just assumed it was that valve again, so I replaced it. I have a LT warranty with AutoZone, so the only cost was the time it takes to replace it (it is a PITA to replace). Replacing it didn't fix the problem. That's when I created this thread.

The only other component that there is in the ABS system is the ABS controller. But what I don't know is where that device is physically located on the truck. Can someone clue me in on that? Before I buy an ABS computer unit, I want to have my truck's in-hand when I go get a new one at AutoZone, mainly because there's a $30 core charge.

[stateranger]

Its inside the dash to the left of the ac controls.

[cgrey8]

How do I get to it? Do I have to remove the dash and AC controls? Or do I get to it from where the gas/brake pedals are?

[cgrey8]

This afternoon, I went looking around under there and found it. There was actually 2 modules mounted together on a bracket. One I recognized as the ABS module and confirmed it was by unplugging it and watching the RABS light go out on the dash. The other I had no clue what it was until I googled the Ford engineering numbers. It's something to do with the windshield wipers. I'm assuming it's the thing that controls the pulse mode and possibly what parks them when you turn them off. And there's the dinger module under there too. I knew about it. In fact, I got so fed up with it dinging when I wanted to have the keys in the ignition with the doors open, I unplugged it LONG ago.

After about 30 minutes of finagling, I finally got the RABS module out. What an absolute PITA getting that thing out was. I'm a little concerned if I'll get it back in there right. AutoZone sells these things for $90+$30 for core. Ebay sells used ones for $17 including shipping. I'll try one of them first just to see if using another one gives me the same behavior and error codes or if the problem persists. Having a 2nd one also lets me open this one with confidence so if I do have to eventually go to AutoZone for a reman unit, I have another core to give them.

In the meantime, is there anything I can do to manually exercise the 2 solenoids on the RABS valve unit from this module's connector? The main thing I want to make sure of is that the valves can work from the RABS module connector location. If not, then perhaps I replaced the old valve unit with a faulty one. Any thoughts on how I might do that? Any wiring diagrams on this thing people know about? In the meantime, I'll see if I can dig something up on the Internets...

[cgrey8]

Well, I just reconnected the module just to see if I could mess around with it and jiggle with it some. I got a different code than I remember before. It's giving me a Code 9, I think. According to some google searching, Code 9 is high resistance on speed sensor. I've already replaced the sensor, so it shouldn't be the sensor. I guess it could be the wiring ASSUMING it isn't the module itself. I opened the case and all the components inside looked good...no burst caps, no burned components. Things actually looked quite clean.

I don't remember getting a Code 9 before. I don't remember the code I was getting before, but I didn't remember it being high resistance to the speed sensor.

I need to get a wiring diagram and do a point-to-point continuity check on the two sensor wires going to the rearend sensor to eliminate the wiring as the cause. I'm sure one of them goes to the module harness. But I don't know where the other one goes...yet.

Edit:
Found this:


What I'm not absolutely sure of is if this is specific to a vehicle (not indicated) or if this is generic across all vehicles that have RABS. As long as the module pinout is accurate and general wiring routing is accurate, that's all I care about. The wire colors may or may not be consistent from year-to-year, model-to-model.

I also found this meaningful as well:

[Grumpy]

Chris....

i got one of them EVTM manuals for the 89-92 rangers if ya want it or need anything copied and posted here ... just let me know.... ill not be using it as im junking my 90 one out and going with the 96 i got ..... my ABS light never was on .... so that means that my module and valve assembly and all is still in good shape (or was when i parked it) ... so if ya need any part.... shoot me a msg and let me know .....

[cgrey8]

Thanks for the offer. I'll let you know.

For now, I have a used junkyard unit coming in to verify it isn't my box. And if the replacement flashes the same code my unit is, then my next task is to verify continuity of the rearend sensor & confirm no issues with the wiring going to/from the sensor.

[Grumpy]

aight...... just let me know if ya need the EVTM or the abs valve assembly or the part in the dash .... ill prob still have the whole truck for another couple months or so .... lol ...... im still gettin my stuff back off it for the 96 ext cab .....