Here is another ABS thread. I replaced VSS and have no difference. Speedo works but above 40 mph it gets erratic, at 55 MPH as I give more throttle the needle will go down to 50 and when I let off it goes back up to 55. CC is just as erratic, I'll set it at say 50 and it will accelerate the truck all on it's own and then shut off. ABS is off when I start the truck and comes on at about 50 MPH. When I first start driving before light comes on the brakes will act like the ABS is being activated when coming to a stop at 5-0 MPH, not at any other speed. So there are the symptoms. Seems drivable otherwise. I have a E99 and 2 wheel ABS.

I did a search and am still reading...lots of info. I pulled codes too.
First one is before I cleared codes, second one is after clearing codes and taking it for a drive, third on is after drive KOER switch. C1229 is the only on I haven't seen before, so that's most likely related to what's going on but I'm not sure what to do about it.

I would also entertain some input on some of the other codes too that don't seem to be affecting anything other than 4x4 doesn't always work without locking the hubs which are new.

 

My truck is also an E99 and had the exact same problem until eventually no speedo, no cruise, no abs. What I did was put a relay for after market lights to a bolt on the grill support right behind the driver side head light, in front of the battery. That bolt holds a green wire which is the ground for the ABS computer. If that bolt is looses like it was for me it will throw the speedo and ABS etc. out of whack. Took me almost a year and half to figure that out, hopefully that's just it for you.

 

I saw your post in my search, I looked for a loose ground there and didn't find one nor did I see a green wire, just black. I will look again on the grill support (didn't catch that the first time). Thanks.

 

Hopefully this helps, don't worry about the black wire there that is for my second fuse box. The green wire goes into a group of wires under the battery for the ABS computer. This is on the drivers side. Again this for an E99 2 wheel ABS. My wire is green but they could have changed the color, not for sure why if they did.

 

Thanks for the picture.

 

Ground looks good, it was a green wire just looked black. Could TPS have anything to do with this? Because I can be doing 70 mph and if I'm on the throttle speedo reads 55mph, let off and reds 70.

 

I was hopping something as simple as the ground wire for you. As for the TPS i'm not to sure, hopefully someone will chime in.

 

I'll have to check the diagrams, but I believe the "reference" signal for both may be the same source.

Be right back...........

EDIT: Nope. VSS does not appear to have a "reference".

Pop

 

So since I only have rear ABS are there any other sensors I should be looking at? Is there anything on the ABS module? What controls the ABS?

 

I only know of the rear speed sensor over the rear axle, hopefully pop will jump in for you.