Hey everyone, I was leaving work a few months back and as I was pulling up to go out to the road the pedal went straight to the floor and I had virtually no brakes. I pumped several times and it did bring me to a stop finally from about 10mph. Before that I noticed going through the parking lot the brakes were surging like a warped rotor almost.

Truck info:
2002 2500
5.9L Mag
4x4 extended cab w/AWAL
130k miles

Initially I figured a line ruptured so I circled back around to the lower lot entrance using the e-brake and all of a sudden the pedal came back and the brakes worked like nothing ever happened. I checked and there were no leaks anywhere to be found. The BRAKE and ABS lights were on at this point.

I had my dad come with the trailer to pick it up because I did not trust it after that and by the time I had it loaded the BRAKE and ABS lights had gone out. I ended up replacing the master cylinder and booster as I figured that the master was failing internally and I always replace the booster at the same time while I am there with the lines unhooked. I have not driven it on the road yet and after thinking about it more I am wondering if this could have been caused by the ABS module failing internally in any way causing the pedal to hit the floor like that and then return and work perfectly fine again. How would I go about testing that? I have had not much luck researching this issue other than I can not read the ABS codes/module on this truck with out a special scanner. All of my other trucks are old enough to not have ABS so this is really my first rodeo with it.

 

If you have already replaced the booster and MC I would do some testing before going any further, my first though would be booster or MC, maybe vacuum issue, I dont think the ABS module would cause a flat pedal because all its doing it controlling the speed/pressure of the flow to the calipers, even if it was stuck open the brake fluid should still push back from the calipers regardless, if you dont see an obvious puddle on the ground I dont think you have that issue

 

What other testing could I do beyond what I’ve done? We bled the system after the new MC and booster and I got one little spurt of air from the front right and that was it. No leaks anywhere.

About 10-11 years ago dad and I replaced the line that runs behind the tank and we put front/rear pads and rear rotors on it. The left rear caliper did lockup one time about 4 years ago but I think that was from the truck sitting for a year or so before any one started driving it again after my grandfather passed.

 

I would be tempted to see if there were any ABS codes in history..... Might tell ya something.

 

I had the battery unhooked for several days when I did the MC and booster so if there were any they are probably gone.

I tried to read them when it was on with a hand held reader from a co worker but I did. It realize at the time that not all readers will read codes from these trucks.

I guess I’ll take it in a few short drives on the back roads and see what it does

 

It should save them, and in the module at that. When I sent our '02 2500 module in for repair they pulled the codes from it. I later realized my old Modis will access these modules.

 

My Innova 5160/5610 (same reader just a different color) will not work on our ABS, the reason why I bought it. My brake and (2 wheel) ABS light are on, I know it's the sensor in the rear I have to replace.

If it drops to the floor the master cylinder is internally leaking. If the engine is off you will still have brakes. It's harder to press because the booster isn't working without the vacuum assist. The other reason is you have lots of air in the brake line and/or the rubber hoses are stretching. Was the MC bled when new?

 

I'm surprised to see the Red Brick still going for $250‐$350 on ebay. That's a lot of coin for a VERY obsolete reader. I think you'll also need a K13 or K13a personality key (sometimes included depending on what the seller has).

An old Modis might be a better choice, and they actually have a scope, too.

 

Sometimes, I've found the old Snap-On MT2500 (red brick) on the local Craigslist and Facebook Marketplace, too. If one is patient, you can find one there pretty reasonably with the necessary cartridges and keys...

 

What model Modis?