ConorToot
Member
No used the new one that came with it.I’ve read your latest post so far three times.
Did you reuse the brake fluid reservoir on the master and did you replace the vacuum line off the master brake cylinder with a new one and use a clamp ?
I think I found the issue and solved the problem, but since it would go away for as long as two days, I don't want to hold my breath until its been a week, possibly more.
With only the ABS pump and control module and the brake booster left that I haven't replaced, I automatically was looking at the ABS equipment and the ECU, as the information that I read said the ECU could cause this. I've already cleaned connectors and I even took the ABS control module apart and re-flowed the solder joints. I was more concerned about the pump or that I might have goofed up when I rebuilt the ABS control module (I had to use a torch lighter to get the 50-ish pin connector de-soldered to get to the other side of the board. I'll be honest, I thought I wasn't going to be driving to work the next day, but it worked.
So, yesterday, Saturday February 24th, I was sitting in my room looking over schematics at almost midnight, then I watched some YouTube videos of how to rebuild a brake booster which they seemed pretty straight forward. I was thinking that I would bite the bullet and order a replacement booster, but when I looked, they were very, very difficult to find new. I'm not into putting used or remanufactured parts on my truck. The reason they are remanufactured is because they broke and I'm not one to put broken parts in as a replacement, nor do I like doing things twice. Then, I saw a video of a guy explaining the vacuum valve and telling the audience to check it with a vacuum pump, etc. It occurred to me that I hadn't done this simple test.
At midnight, I went out to check the vacuum valve and lines. When I went to pull the valve from the booster, I noticed it wasn't seated all of the way in, which at first didn't alarm me. I checked the valve with about 20psi of vacuum pressure and it worked great. I reinstalled it and did something my brother-in-law had recommended that I already checked, but thought it wouldn't hurt to do it again and that is to pull a vacuum from the vacuum valve with it installed to check the booster's diaphragm for leaks. It was fine. A little dejected, I got in the driver's seat and reset the fault code and took it for a spin (also to get some late night Whataburger).
Typically, it only takes a few minutes for the light to come on, but I noticed after my munchie stop that it still wasn't on. This wasn't shocking as I've had it go two days without coming on. The more I drove the more I recalled the valve not being fully seated and pondered how this could cause a comparative pressure whatever it says for C121E in oddly phrased diagnostician English. This morning, I got up and had to run to the grocery store. The light was still off. I drove it once in the afternoon and by this point, it would have likely come back on by now, but it was off. When I got home, I pulled the valve again to inspect the seal. It wasn't bad and the valve fit fairly tight, but it was pretty dry. The rubber still had a decent spring to it, but I could see how it might not seal well against the hard plastic of the valve itself. I had an assortment of good quality o-rings in my garage, so just for s&giggles, I found one that was a fat o-ring with lots of bounce and a snug fit for where the valve mates up to the booster seal. It was installed and I went on another drive. Still no light. I'm about to hit a grocery store for some lunch supplies and maybe its still sealed and the light is still off? Like I said, I'm not holding my breath because nothing pointed me in this direction and I don't know why that seal with a leak would cause a C121E fault. If anyone has a hypothesis, I'm all ears.
I’ve read your latest post so far three times.
Did you reuse the brake fluid reservoir on the master and did you replace the vacuum line off the master brake cylinder with a new one and use a clamp ?