1997 Ford F250 LIGHT DUTY ABS/Brake lights on - cannot read fault

So, my 1997 F250 LIGHT DUTY (ones with the 7 lug rims) has decided to throw another curve ball.

I was driving down the road and noticed the ABS light on. Later I noticed the brake light was on and am not sure if that was on the entire time or not. The brakes seemed fine but I took it to a parts store and had the codes read. The engine codes could be read fine but the ABS codes couldn’t. I decided to go to another competing parts store with a different reader and it couldn’t communicate either. The error both times was something like “Failed to establish communication with vehicle.”

Brake pressure feels normal, braking feels normal, and the fluid levels are at the full mark where they belong.

I am wondering if there is a wiring issue or the ABS module has completely failed but have the truck parked until I gain more insight into this or take it to the shop for them to figure out.

Any ideas?

There may be a bad connection, or the ABS sensor on the differential may have failed.



What we have heah is a failure to communicate.

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If the reader COULD read ABS code but could not communicate with the ABS, it is likely the electronic control unit for the ABS has failed. I consider that likely given the age of the truck.

I expect once you get access to a properly configured scan tool you’ll be able to retrieve the diagnostic code(s) from the ABS module. You may need to get the ABS codes read at a Ford dealership, they’ll have the correct scan tool for your truck. Before that, take a look in the area of all the wheel speed sensors, maybe a wire is broken or disconnected.

Before you start condemning the ABS module, I’d make sure power and ground to the module are good

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I have had electrical issues due to corroded wires in the past so that is a good idea to check grounds and such. I assume they are under the dash on the firewall???

It appears my truck has two wheel ABS. The wheel speed sensor failed in the past but I got a code for that which was resolved when I replaced it. This time it just cannot communicate. Either way I will check the wiring to this.

1996 and earlier used flash codes. You have to ground the always hot wire going to the unit with the key on to not let the memory be cleared. It’s under the dash near the middle somewher. There is a connector that comes apart. 1997 might still be the old style. Is it still the classic frame style? Then the flash codes activate.

You could have low brake fluid, or the brake pedal could being pushing down too far and tripping the sensor at the end of the master cylinder.

The fluid level was the first thing checked and it was good. The truck is the new style but ANY car made from 1996 on is OBDII by law, including the holdover square body super duty trucks using the otherwise older technology. Also, it isn’t the OBD II module giving me trouble. It is the ABS module which may or may not be bad. I need to dig in and find the grounding point for it.

We had a few of those 1997 F-250 7-lug light duty trucks in our fleet for awhile and I seem to remember they had 4-wheel ABS . . . ?

Isn’t the ABS hydraulic unit and control module in the engine bay?

I was under the impression the ABS computer was up under the dash. I need to figure that out for sure before tearing the dash apart. I am more concerned about the computer as it cannot even communicate. Yes, it was configured to read the Ford codes according to my VIN number at both parts stores. Both used a slightly different reader as well so I think that is also related to my truck.

Is there a control module in the engine bay and a computer elsewhere?

This truck has DRUM brakes in the rear which I remember someone saying is really odd. The speed sensor on the rear is in the differential as someone posted a picture of earlier if that say anything. I need to figure out if these trucks are 4 wheel or 2 wheel ABS as I am finding conflicting information about that as well.

I might just take this to the shop and be done with it as it is a potential safety issue and not just a simple brake job. .

Easy, does it look like you have one or two brake hoses on the front… The odd looking 2nd one is the ABS sensor wire… If you don’t see a second one then RWABS only…

Wikipedia says the F-250 light duty is just a 10th generation (about 1997+) 7 lug F-150. Ford F-Series (ninth generation) - Wikipedia

RABS II is a dump only (release only) rear only ABS with a sensor in the differential. The valve unit is probably by the left front wheel by the brake line that goes to the rear on those. It was just to prevent the rear wheels from locking up and preventing the driver from losing control of the truck. edit: I confused the requirement with the requirement for airbags. ABS came in 2012. I think the legal requirement for ABS in the front was in 1998. I’m interested to see what your truck has has.

My 1999 Dakota was RWABS and it sucked… My 2002 & 2006 Corolla’s did not have ABS at all… So, not sure what you mean by that??

I must have been confused with when airbags became required. Apparently ABS wasn’t required until 2012. But this site says 2004 so I’m still confused! When did ABS become standard on all cars? | Jerry

If the brake warning light and the ABS light are on it’s probably low brake fluid sensor. The only other thing that turns on the brake warning is the parking brake.

Strange, I am finding a lot of info saying 2004 also, but a few September 1, 2011…
I can’t tell you when is was required by law, but I can say that my 2006 Corolla LE didn’t have it… That was a big selling point for me, but ABS was an option on it…
Maybe 2004 was required to at least be an option but not required to have until 2012??.. :man_shrugging:

My brake fluid level is full. I will check into this further before calling it quits. If the ABS module is in the engine bay, then it should be an easy fix and maybe it is just some bad wiring which is very possible. If under the dash, I might just take it in to the shop. I will look and let everyone know.

If I remember correctly, on a 1997 it only had rear abs. and I believe the module is behind the dash. the 04 F-150 I had 4-wheel ABS and the module was located on the driver’s side under the hood.

From what I can tell, the 4ABS module is under the hood, driver’s side, toward the front/top of the left front wheel. To the left of the module (towards passenger side) there’s a radio noise suppression capacitor, cylinder head temperature sensor, and intake air temp sensor. The PCM is also under the hood, above the passenger side front wheel.