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Micro Machine Manager
Second malingering issue I'm tackling on 92 F-150 Custom (RWD, 300-6 E40D)

I had purchased a second RABS I Module and swapped out after repairing the front brake line system just to be sure no hang-ups were there last Summer. The light continues to come on once I get above 35 mph and hit a nice bump. Two years ago I had replaced the Wheel Speed Sensor on the back differential there. The Pinion Seal is leaking so I probably need to learn how to crack that open -- oil is black as night. Unsure if that could cause the RABS light to illuminate?

I checked the gears through the hole where the Speed Sensor went once I popped it off -- looked ok. I replaced but sad to say the light comes back when I get above 35ish mph.

The leaf springs are due to be changed out. I have a set of F250 Springs installed and 1 of the leafs is cracked on the right side, but everything else is holding together. Still, that is on my to-do list and remove all the rust/paint/rubberize after install to give the frame and springs a good shot at another decade.

So after changing out the ABS Control Unit last Summer, repairing front lines, checking back lines for brake bleed hangups on the drum brakes, changing out the Wheel Speed Sensor for the second time in 2 years, etc and changing out the ABS Module with no change, as well as a failure to be able to pull codes from the ABS Module, I'm leaning towards a broken wire but where to begin looking for the broken/corroded wire?

The junked oil in the differential probably could throw some bad codes to the ABS Wheel Speed Sensor, but it shouldn't inhibit pulling codes which leads me to a broken/corroded wire.

I'm replacing my 7-pin and wiring today along with custom license plate lighting and adding some weatherproof improvements to that wiring and found a corroded blue brake control signal wire by my Fuel Filter that has been repaired once already in 2018 on the road, so I'll be installing upgraded weather-proof lines and connections (and soldering, yeah!) for good integrity. I got my photovoltaic equipment with me, so I can test just about any DC type circuit for amps and voltage (I know voltage is primary here anyway for auto diagnostics) if anyone has suggestions on where to look for an ABS wire crimp/break/corrosion issue that would cause the following symptoms.

1. RABS I Control Module will not provide codes no matter how many ways Code Test is initiated (will not begin test).
2. ~35 MPH RABS Light will always come on.

(3) Only ECM Code is 327 for EGR Sensor. Gonna clean out EGR later, install new one and if anyone knows the voltage to check the pins, want to make sure those are good as this is a persisting code and more likely needs pig tail replaced rather than actual sensor.

Link provided to my Google Drive with Wheel Speed Sensor port open to inspect teeth. I felt them with my seeing-eye nubs and didn't feel anything I thought was odd, but it's my first time putting any of my 21 digits in there. Maybe I just don't know. Oil was gritty, but didn't feel like metallic shards. Think it's just really dirty and due for a new pinon seal and flush.

RABS Wheel Speed Sensor Port Inspection
How are you pulling your codes? I use an Innova 3145 that i've had for a few years and it is a lot easier than counting flashes. If you can't get any more codes from it i would firstly drain and flush the diff out , replace the pinion seal and give her a good old birthday shout with some new fluid.

Not working above 35mph is a little odd and could be vibration related (unlikely) , could be that the sensor is actually tripping something at that speed or enough of that ugly fluid with suspended metal particles is upsetting the sensor. Cleaning and replacing diff oil is something that needs to be done and will rule that out.

You could download a wiring diagram for that part of the system and clip a lead long enough to reach the rear of the truck from the front plug to check continuity through each of the wires ..... you'll need someone to crawl along the chassis rail shaking the wiring loom while you do this to see if there is a break in the wiring.

And lastly (but should have been firstly) , these trucks are getting old and all the earthing points are getting corroded and have poor connections - clean and reterminate all the grounding points you can find - chiltons manuals have pretty good wiring diagrams that show earthing points that are in the oddest little places.


Micro Machine Manager
And lastly (but should have been firstly) , these trucks are getting old and all the earthing points are getting corroded and have poor connections - clean and reterminate all the grounding points you can find - chiltons manuals have pretty good wiring diagrams that show earthing points that are in the oddest little places.

That's pretty solid. I'm thinking you're right on the process.

First Pinion/Differential Gasket n flush, then will work wiring and grounding for the last best effort. New grounding all in the engine bay, thinking it's likely a wire between the ABS and CMD or ABS and Speed Sensor grounded/shorted out and interrupting fault codes.

Yeah, I got a code puller that reads out the numbers as it flashes and stores them. I'm pretty good at counting the flashes too though and referring to the manual. Just code 327 atm although the Engine Light is staying solid now, so I'm gonna pull codes again since that's new after putting a new ABS Speed Sensor in.

Cannot cause the ABS I Test to start via short out (negative or ground to pin) at the test connection under the glove box while applying power whether it's accessory or engine running, so I cannot get ABS I Test codes (which are separate from the ODB1 port). It leads me to think there's a wire somewhere that's the problem after fixing up all the other components (Speed Sensor x 2, ABS I Control Module x 2). I highly doubt I have 2 bad of everything. And a brand new ABS Control Unit running the brake fluid/pressure as of last Summer (it needed it, that thing was gonna fail any year now, original equipment for sure).

Any recommendations on the Pinion Seal Kits available out there for 92 F150 RWD 300-6 auto trans? Original differential despite F250 leaf springs above it. Probably the 8.8 inch type? Differential Gasket is kinda Square-looking on the back side. I know I know, how many bolts. I'll go count.
It does sound very much like a wire .... just need to check out each wire which can be a bit time consuming.

I use Rockauto for a lot of my parts as many other companies won't ship to NZ ... here's a link to your trucks driveline parts.


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