2003 V-6 Alero with Anti-Lock, Trac Off, Service Vehicle Soon dash lights on. Pulled codes with my Blue Driver and had multiple codes for both sides front ABS. Replaced both hubs/wheel speed sensors and got it down to just one C1232 ABS code. It is for an open or shorted left front ABS wheel speed sensor circuit. I then replaced the harness on that side but it still has the code. Then I did more investigating after getting more knowledge. After disconnecting the wheel speed sensors I checked for voltage from the ABS module on both sides and were about 5 volts. Then I checked the resistance on the wheel speed sensors. Left side was about 1100 something ohms and the right was about 1030 or something like that. The big harness plug on the ABS module was interesting to remove but after removing it both sides (all four wires) had good continuity from the plug to the wheel speed sensor plugs. The ABS plug and socket looked really clean and I did not see any green corrosion. I also checked the resistance of the wheel speed sensors again but this time from the ABS module plug and were both fine. Then I put the front of the car up on jack stands, disconnected the wheel sensors, hooked my ohm meter up to each side, started the car and put it in drive. With the speedometer reading about 20 MPH the right side went to about 4300 something ohms and the left was about 4500 something ohms. This is driving me nuts. I can clear the code, those three dash lights are off, back out of my driveway and as soon as I go down the road 50 feet the dash lights come back on. Bring it back and has the same C1232 code. No where on the internet can I find where someone has replaced an ABS module and cleared that code. (or the right side equivalent code) There are places that repair those ABS modules but I have not found one yet that repairs this one. Some people have re-soldered the circuit boards with success but there again not this model. I found used ones on eBay for $50-$125 but from what I understand they need programmed to the VIN. Same goes for a new one. I found this on the Impala forums but even though it looks similar I'm not sure it is that same model. It looks pretty tricky but I might try it as I am decent at soldering. Any other ideas before I try this?

https://www.impalaforums.com/threads...d38ZisPw5AXumI

From the old hubs, do you have one that was still good before replacement? It would be a good unit to temporarily connect to the electrical connection to see if the problem changes.

Best to read this in frequency rather than resistance. The sensor produces a sine wave that a standard vom will read in hertz and should go up with wheel speed and shouldn't drop out. I like to use a scope or even a graphing meter so you can see the strength (amplitude) of the sine wave. Most need to be at least a .5V for the PCM to pick it up. I've seen brand new be weak and set codes.

The wires got pulled out of the hubs when removing them but I saved the connector plugs to make test harnesses. Even if I connected temporarily I'm not sure it would tell me anything. It only threw the code after the car started moving.

I saw a few videos where people were using those and it was interesting. Many times the bad sensor would show an interrupted pulse on the screen. I looked into buying one of those and saw several portable or handheld versions for under $100. The ones that were a combo multimeter/oscilloscope that had a larger screen than a typical multimeter looked the most handy for automotive work. Even though you usually get what you pay for they still might be good enough for the home mechanic.

If I made two harnesses so that I can swap the left speed sensor to the right side harness and vise versa then that should tell me if it follows the wiring or hubs/sensors. Somewhere I read (you know how that goes) that in the late 90'* GM'* diagnostic software had it backwards on the front left and right wheel speed codes. Surely even if that was true they would have fixed that by 2003 but I just can't get that out of my mind. Just what if.....

I got to thinking about CathedralCub'* post. If the wiring harness was actually disconnected or shorted would it throw the code right away or does the car need to move? I'm sure I could find out myself by trying that but wanted to know how it is supposed to work.

I was thinking of recommending this but didn't want to suggest something too crazy yet. Looks like you were thinking the same thing. Doing this would certainly eliminate a lot of possibilities.

I started the car, cleared the codes (the three dash lights were off already), then I pulled the left front wheel sensor plug. It immediately lit all three dash lights and of course the C1232 code. Well at least I know the answer to one of my questions. Now for the part where smoke starts pouring out my ears. I made up two harnesses to swap the left wheel sensor plug to the right side chassis harness and vise versa and plugged them in. Started the car and with the front on jack stands put it in drive. At idle (15-20 MPH) no lights came on. I got it up to 30 or so and the Trac Off light came on briefly (probably because the rears were not spinning) and then it would go off. I did this several times with the same results. I pulled codes and no ABS codes.(I still have a bunch of others that I believe are unrelated) So the problem went from being very consistent to now apparently intermittent. I'm going to try to tape up and zip tie my wiring mess, put the wheels back on and drive it to see what happens. Maybe the new hub (if that is the issue) will have more pressure on it from the weight of the car and steering to fault out.

Okay. This is getting stupid. I drove it around the block with no lights on dash and no ABS codes. At that point I thought that maybe the new hub was made with the sensor too close to the teeth and after so many miles it wore down to where it didn't intermittently short anymore. Then I put the plugs in their proper places and no lights at first start up but as soon as it went into reverse the lights and C1232 came back. Next I'll remove the ABS module plug, hook my ohm meter to those two wires on the plug, wiggle the harness and the wheel sensor plug connection to see if I lose continuity. It seems like I have to fiddle with that plug a bit to get them to connect so maybe that is the issue. Once the harness pushed one of the pins out of the wheel sensor plug when I pushed them together and I only noticed it later when I disconnected them and flipped it around to look at it carefully.