Service trailer brake system and ABS light on?

I was driving at highway speed and my dash light (ABS) light came on. About two miles later when I came to a stop my speedometer needle was bouncing from 0 to about 35 while stopped. Upon leaving the stop sign I had first and second gear but no other gears. I have scanned this vehicle and get a C0550 code telling me that I should replace the ABS speed sensor that is located on the tail housing of the transmission. I have done this twice and checked the two wires that end up at the ECU for damage. I changed the transmission oil and filter for the first time ever and found what I would consider very little deposits on the magnets. Upon test driving it again the scanner tells me that I now have code C0550 and that a common repair for this is to replace the ABS control module. I was getting the ABS code about every ten to fifteen miles that I was driving. I can cycle the key to clear it. I experimented with driving in the 3 position instead of D and I was able to go 120 miles with no issues. It appears to me that the issue is related to fourth gear and that something is not reading the speed sensors right, or I have bad sensors or modules. When the code is not present the transmission seems to function properly. If it turns out to be a ABS module, do I need to get it flashed or programmed or is it just a nut and bolt swap?

Ken,
I replaced the module with a factory GM module with the exact same part numbers on it. Upon start up I had an ABS light and a brake light. I drove it for a test drive about six miles and I lost all of my gauges as well as the shifting problem returned. I brought it back to the shop and was going to trouble shoot some more and when I tried to start it the truck would not even crank. I put the old module back in and ordered another new one. The second new ABS module allows me to start and drive but the ABS light is on and after a few miles the speedometer starts bouncing again and shifting becomes erratic. The code that I have now is C0569. Are the modules a programmed or learned unit? Am I looking at an ECU module? Suggestions please. The scanner seems to communicate okay with the ECU as I can trigger the ABS pump, check for four gear lock up and shifting patterns okay. Please let me know what you think. Thanks. Gary

Good evening all,
Today I started from scratch. I tested the front L/R ABS sensors and they tested good. And when disconnected gave me a code. The ABS speed sensor tested open in static mode like it is supposed to and has been replaced twice with a new one just to make sure. The ABS brake module has been replaced twice this week to try and insure a properly working unit. I ohmed out the wiring harness from the ABS speed module on the tail housing to the pin connector on the ECM. I disconnected the ground cables (three) of them from the chassis, ground the steel with a grinder and file before reassembly. I have a good circuit from the ECM to the ABS speed module on the transmission. At present I have a steady ABS light and a steady red brake light on. While driving the transmission works fine for about fifteen miles before issues arise. When the issues start, at idle with my foot on the brake, the speedometer will start to bounce from zero to almost seventy mph. If I try to take of while the speedometer is up there the transmission kicks in hard. I have no ABS brake function but the brakes work well with a good pedal. I have current codes of C0569 and C0550. I have tested each and every fuse under the hood and the dash. At this time the truck has had three ABS speed transmission modules and two ABS brake modules. I phoned the local GM dealer and was told that if I purchased an ECM programmed from them that the bill would exceed $1,000.00. I think that about covers what I did today. Thanks for any advice. Gary

Hi, my ABS light just came on today. Once in a while I hear grinding coming from the tire. Replaced wheel bearing month ago so I know it is not that. What could it be?

Hello to all,
Sorry that it has taken so long to get back to you but I took the truck to the GMC dealer and they had it for four weeks and three days trying to figure this out. The short version of this goes like this. They removed all of my new parts and reinstalled the old ones. Then the first thing that they did was replace my ABS sensor in the transmission again. Then they rewired the transmission ABS speed sensor. Then a Transmission Control Module was replaced and programmed. Then they replaced the left front hub and spindle assembly. Then a new ABS sensor for the left side was replaced. And finally the left side speed sensor was rewired going to the ECM. Finally the abs lights are off. In the end what it appears to have been was bad wires from the left side front speed sensor to the ECM. Did I mention four weeks and three days. At one point I was asked if I wanted the ABS brakes and lights to work as the truck seemed okay with them on. Thanks for your suggestions guys and trying to help me out. G

ABS and brake light comes on at start up, no codes found, clear light with scan tool, lights stay off until key is cycled, then they come back on. No codes found? Drive cycle test shows all wheel speed sensors working.

The brake fluid level is fine, my son just purchased the truck. The lights were on when he got it. We installed new pads and rotors for and after.

That is Forward and AFT.

Brakes problem
2006 Chevy Silverado V8 Four Wheel Drive Automatic 174k miles

the abs brake light is going on and off-mainly on-when its on theres chatter and movement in the petal and you can feel it in the steering wheel when applying the brakes, -note- both front wheel bearing housings have been replaced recently-6months-1 year.

Blower motor and cruise stopped working at the same time my anti lock brake light came on at the same time