Hi yesterday was the first day with snow since i got the 1990 f250 and i found out that it is braking most on the rear (spooky braking...sideways) Then i discovered that PO painted over the rabslight in the dash and it is on always. I cant seem to find any guide/test to sort out whats wrong.

I have a new vss sensor in rear diff and speedo/cruise/e4od works perfekt.

Any ideas or pointers?

Kent

 

Just a couple things to check...

Since the PO covered the RABS light, I wonder if he by passed the RABS valve on the frame rail under the drivers feet.. He could have also unplugged the RABS module under the dash behind the glove box.

 

I don't know about a '90, but on my '93, the RABS module will store DTCs. Have you tried reading codes?

 

Tomorrow i will check both rabsvalve and module for connection. Could be disconnected or bypassed in some way.....

Any info on how to read codes? my manual only tells me what codenr. mean not how to read them

Thanks

 

There are lots of code readers available. It can be done without a reader, but it's a pain, and cheap readers can be had for like $30 at the auto parts stores. A good reader is a lot easier, and can be used on lots of vehicles... I think Whites hypothesis is good; if the PO painted over the light, there's a good chance the module is un-plugged.
Good luck!

 

My 90 F 250 ABS light comes on after a few min...about a mile of driving got any Ideas on mine too !!! Please and thank you !!!

 

Phy, a code reader will not read RABS codes as the RABS computer is seperate from the PCM.
You need to look under the dash, probably above the parking brake pedal for the RABS diagnostic connector. Should be a black wire with an orange stripe, I think. Then, with the ABS light on, momentarily ground the diagnostic connector. The ABS light will then blink out an error code. It will be a code between 1 and 15, I think. There will only be one stored code. If there is more than onr fault then the first one has to be fixed before the computer displays another.

 

OM you can do the same to get codes but the ABS light must be glowing steady as every time you switch the truck off any code is erased.
Check that the brake fulid resevoir is full and that both brake lights are working properly.

 

Thanks its always nice to be able to read codes... if the module is connected. Havent thought about checking fluidlevel

Thanks

 

Thanks, LK, I didn't know that.

 

and the sensor in the rear is abs only. the 90 speedometer is cable driven off of the tailshaft of the trans on 2 wheel, and output shaft of the transfer case on 4X4. the cruise sensor is part of the speedometer cable assembly.

rear axle VSS did not start until the introduction of the digital dash in 92.

 

Hi

Have worked on the truck today and i found out both the rabsvalve and module is connected. It reads a code 7= no isolate valve selftest

Does anybody have the resistance and wirecolors so i can check it to se if its a broken wire or defective valve

Thanks

 

Don`t know the wire colors but on the RABS hydraulic module the resistance of the isolation solenoid should be 3 to 6 ohms and the dump solenoid should be 1 to 3 ohms. From what I remember there are only three wires going to the RABS HC module and one is probably a ground so check between it and the other two.

 

Thanks now can test it. Its 4 wires

Anyone know where i can get a good shopmanual for my truck?
I have a Chilton very limeted info/specs

 

Check out ebay.com and helminc.com for a manual.