About ten or so months ago my trany was slipping into neutral like state while going down the highway. After much reading I put a transmission range sensor in and it fixed the problem completely. Now it's slowly doing the same thing but acts like it's getting lost between second gear and drive and Tha abs light randomly comes on. I went ahead and changed the speed sensor over the third member cause it was cheap. Didn't help. The only code that auto zone found was "range sensor voltage too high". So could the range sensor be bad again in such a short time? There were no abs codes.....I'm stuck. 1994 f350

 

ABS codes can only be read while the ABS light is on. Once the ignition is turned off the code is lost. You will have to wait for the light to come back on to check the codes. Reading them is also different from reading engine codes. There is a wire under the passenger side dash that must be grounded, or something then the ABS light will flash out the codes. I can't remember the procedure off the top of my head, but it's on the forum somewhere.

 

RABS-II has a Keep Alive Memory circuit. It will keep stored codes. I believe around 1992 was the change over. Perhaps a little earlier.

 

Pretty sure my 1991 is before the crossover. Maybe it is also the difference between RABS and ABS?

 

This vintage F-series truck only came with Rear Anti-Lock Brakes (RABS). 4 wheel ABS was only available on the Bronco and a completely different system.

RABS-I did not keep any codes after shutting off the vehicle. RABS-II has that feature. My 1993 EVTM shows Fuse 13 is for the Keep Alive power on the RABS controller. So it looks like 1993 was the first year for RABS-II.

 

I ended up changing the range sensor again, that fixed the shift problem. The ABS light was coming on becuse the rear tail lights were not plugged in. Everything works fine now. Thanks for all the replys!

 

Glad you found it. Thanks for replying back.

 

I noticed you post with the same problem I'm having to my 1990 F250 and am curious if anyone could help me further in finding out the problem why my ABS rear light stays on and can’t get any flashing from the light to read the codes. I tried grounding the pin next to the emergency brake to get the light to flash codes but had no effect to light. Light would not flash just stayed on all the time. When turn the key on positions the rear abs light comes on, then goes off for second then comes back on and stays on.

I have replaced my master cylinder and vacuum booster because of loud hissing sound when brake pedal was pressed to floor. New vacuum booster made it quieter. Brake pedal is firm after couple pumps and only moves about 1 inch to floor when engine is off and key is on position. Keep pressure on pedal with engine off and does not move closer to floor. Start engine, pedal moves 2 inches closer to the floor and fills little spongy when keeping pressure on pedal. Does vehicle brake pedal supposed to do this when engine is running the vacuum system?

I replaced RABS hydraulic valve and bleed brakes (RR, LR, RF, LF) but still doesn’t fix spongy brakes or light staying on. Replaced ABS rear sensor couple years ago but did check it for resistance again and reads about 1000. Went and bought a new one to cross refence the reading to mine and new one is higher at 1900. does anyone know what the correct ohms reading should be on the rear ABS sensor? I unplugged ABS control module and plugged in a used one I got from a junkyard to see if it would correct problem with light staying on. Did not affect the light staying on or brakes being spongy with more movement toward the floor. It also didn’t fix the problem of not getting the ABS light to flash when I ground out the plug pin. So, plugged back in original control module. I am felling it is a wire issue or connecting plug issue of grounding issue. I notice a post of rust problems and grounding http://www.mightyautoparts.com/pdf/articles/gb0804.pdf but the link does not work. Can anyone help me in how to check plugs and wires or grounding issues that may solve my problem would be very helpful.