Electric Vehicle Forums - ABS Light on Regen Brakes Disabled with 3 codes, HELP!

I am not qualified to answer your question, but here are copies of the two posts that I shared with a Ford dealership mechanic: Btw, haven't had one problem in nearly two months. Very grateful to both of them, smarter than dealership.
1) Originally Posted by Hackman https://www.greenhybrid.com/forums/i...s/viewpost.gif
I had the problem of no brakes. Cleaned all the ground connections from battery to the frame. I have had no problems in the last 2 years. 1 under the battery 1 behind the front wheel and 1 on passenger side firewall.
Has anyone else tried my solution? I had the car for three years after the fix and had no issues. I think when a new hcu is installed, a secure ground connection is reestablished, that is why the replacement seems to work.
2) Originally Posted by Lordofrealms https://www.greenhybrid.com/forums/i...s/viewpost.gif
All,

First a disclaimer, you accept all liability for any damage you cause directly or indirectly from following these instructions and they are provided for education purposes only. You will be working with your brake system and can cause it to fail and cause an accident. If you don't understand any part of this or do not feel qualified please do not contemplate doing this procedure.

Now that the legal disclosures are out of the way... I wanted to give some insight in to what I did to fix my brakes on my FEH that kept having the issue listed above and throwing error codes about control plausibility failure.

Essentially what is happening is the ABS module is detecting that it cannot properly apply the brakes to one or more wheels and then disabling that wheels brake and the one diagonal to it. Also, it may go into safe mode where it is not controlling the brakes using the brake by wire system at all and instead you have to manually brake at the bottom of the brake peddle.

Here is what I did to fix it:

1. First, I got a CANBUS bluetooth interface. It is like the ODB error readers you can borrow from AutoZone etc, but it interfaces with your computer. You can get one here for about 11 bucks:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

That is the hardware that will plug into your car and allow you to interface with all the different computer modules that control your car. However, you will also need software on your computer to interface with that hardware. There is a free program called FORSCAN that will interface with that bluetooth module and allow you to read DTC (Digital Trouble Codes), reset them, and also reset the ABS module.

You can get FORSCAN here and its FREE: http://www.forscan.org/

As a temporary fix, you can reset the ABS module in FORSCAN and it will start working as normal again until it decides to mess up. I typically had to reset the module then when it says to turn the key off make sure you also remove the key and open the drive door. This tends to ensure that it fully resets. Then follow the rest of the on-screen prompts.

This however, is not permanent and as soon as it got hot in the engine compartment (usually from sitting still and running the AC) it would trigger the same error.

2. I did the solution posted above of cleaning the ground connections. I actually, couldn't locate the one in the driver wheel area so I just did the other two. I used some sandpaper when I cleaned them so I removed all the dirt and gunk and also scrapped up the paint to ensure good contact. Then put the ground connectors back on. I don't know if that in itself was enough to fix my problem, but it could have been.

3. I think this was ultimately the solution for my particular case. My brake fluid had never been flushed/changed and I had 140000 miles. I flushed the brake fluid until I got perfectly clear fluid coming out. I didn't have anything to remove the fluid from the reservoir so I just got three large containers of DOT3 brake fluid and kept flushing until it came out clear.

Here is the process for that and unfortunately since this is a hybrid with a brake by wire system, and an all electric system, it is a little different and there are some important things to consider.

The way the brake by wire system works there is an electric pump that builds brake pressure into an accumulator (a place where a small amount of high pressure brake fluid is stored to be used via the electronically controlled valves in the ABS module).

If you completely empty this accumulator there is a chance you will be unable to get it to fill it back up without special tools. Therefore, ensure you understand this process before you begin.

There is also an intermediate problem before you completely empty the accumulator where you can trip a pump failure detection on the ABS module, if that occurs you can clear it by an ABS module reset and resume bleeding the brakes.

I did this as a 2 person job. One person attached some 1/4 tubing to the brake bleed valve nipple then ran it to a funnel and held it. The other person with the key on inside the vehicle would depress the brake peddle about halfway.

IMPORTANT: As soon as you hear the brake pump kick on you need to IMMEDIATELY stop and let off the brake. Again, if you keep going once that pump kicks on you will either trigger the pump failure or worst case empty the accumulator.

Wait until the pump kicks off then repeat the process. You should be pushing substantial amounts of fluid out each press. After 5 or so cycles of this you will need to stop and refill the reservoir.

IMPORTANT: Again, if it goes completely empty, you will likely both get air in the system and possibly empty the accumulator. Both of which are very bad things so its worth it to refill the reservoir more often than needed.

Continue repeating this cycle until the fluid you get out of the bleed valve is completely clear and not urine colored (or brown if this hasn't been done in a very long time). You will want to start with the driver rear wheel then the passenger rear wheel then the driver front wheel then the passenger front wheel. Whenever you finish with a wheel you will want to close the bleed valve in the middle of ejecting fluid from it so that the system is completely air free.

I used about two bottles of fluid before I finished with the first wheel. Then since I had flushed the reservoir and most of the lines doing that wheel, the other wheels took maybe 2 5 pump cycles and they were done. It took maybe an hour to do the first wheel and 30 minutes to do the other three.

You will likely have to jack up the vehicle and remove the wheel to get to the bleed valve. It can be done without doing so, but it makes it a lot easier.

Once you have bled the valves on all the tires then you just need to do an ABS module reset with step 1 and then road test it to ensure you didn't get any air in the brakes.

I hope this helps someone who gets this problem in the future. If you have any questions please let me know. Thanks!