ABS light problems/Transmission problems/speedometer problems

I have a 2008 Silverado 1500. I started having problems with the transmission out of the blue not wanting to shift out of 1st gear when taking off from a red light or just taking off. I could manually shift to 2nd but that was it. Pull over, shift to park or just stop and it would miraculously fix itself. Next, started getting ABS light with no apparent symptoms while sitting still. Got to noticing that while this was going on, the speedometer would be bouncing from 0mph up to 10mph while sitting still. Take off and no more bouncing. I was going through a drive through yesterday, and noticed when easing on and of the brake I could feel the brakes grabbing and letting go while easing up in the line after the ABS light came on sitting still in the drive thru. Finally realized by OBD code reader could pull the ABS codes and got a U0073-00 and a C0055-5A. The first is a generic the ECM can’t connect to another device (not specific) from what I could find. The second is telling me the rear ABS/Speed sensor is sticking open or shorting out. Correct me if I am wrong, the bad sensor would be causing all of my problems and the 2 codes are actually related? New sensor, problems solved?

Maybe, but you may have a wiring problem. Or maybe even just a dirty sensor or tone wheel.


I had a 2003 Olds Silhouette. After about 12 years, it threw an abs code. I read about GM abs sensors getting dirty and misbehaving. I pulled the connector apart, then tried to get the sensor off the wheel assembly, but couldn’t. I tried again another time or two, connecting and disconnecting the cable each time. After the last time, the code cleared. It must have been corroded terminals in the abs sensor connector at the hub and the abrasion when manipulating the connector rubbed the oxidation off.

You are likely correct.

So are there 2 ABS sensors on the back or the one? I looked under with a flashlight a few moments ago and only saw the E-brake cable and metal brake line going to the back wheels. No sensor on the wheel area as I saw in other videos

I have looked at the following videos and my truck does not have this in the location shown.

I haven’t looked at the videos you linked yet, but I will. I was thinking the speedometer read off of a speed sensor on the tail shaft of the transfer case (4wd) or the transmission (2wd), but that might be on older models. Would affect transmission shifting, not sure about the abs light.

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I think scrapyard-john is correct. I found this. it might be the same on your truck.

on the 2008 GMC Sierra, there are only two ABS sensors – one for each front wheel. The vehicle speed sensor installed in the tail section of the transmission acts as the ABS sensor for the rear axle.

I get what you are saying, and I know that’s where the speed sensor or cable used to connect in the older models. When I look up the part, I find this:

It clearly shows the cable that I don’t see. I guess they are different on different models?

And what I am needing is actually a speed sensor and not the ABS?

May be different for different models. Some may have “stabilitrack” as GM calls it, some may just have simple rear ABS with just one sensor. I think on the tail shaft it’s just called a vehicle speed sensor.

I’ve had kind of hit or miss luck with Dorman. I’d try to get a Delphi, AC Delco, or whatever other oem supplier brand if I could find it.

Not set on using that particular brand, was just using it as a reference photo for myself so I knew what I was looking for. I appreciate the help and will crawl underneath tomorrow when I have more light.

on rockauto it is called an ABS Wheel Speed Sensor for your vehicle

I think this is it on Rockauto

Sorry for the delayed response. I ended up changing the speedometer sensor on the transmission and knock on wood, no more problems with the brakes or shifting. Thanks for the help and hope this helps someone else down the road.


The car’s powertrain control electronics uses the vehicle speed as a primary input. If that’s faulty, no telling what symptoms might appear. In the computer business they say GIGO … garbage in, garbage out.