So these lights popped up recently. Truck has been running like garbage. Sounds terrible like bad rocker noise since these lights came on (which I found was quite odd, although these lights temporary went out one day and truck sounded fine again). The cruise control don't work either.

So I hooked up the old computer and found these
U1417 - implausible left wheel distance signal received
C1020 - left rear wheel speed circuit sensor
C1027 - left rear wheel speed sensor signal erratic performance

I'm guessing from these codes that my left rear abs sensor is toast? Should I just replace the sensor or also the harness and wiring too?
Is there any chance it may be the sensor located on the diff?

Any suggestions appreciated. Cheers

 

How many sensors do you have back there? Is there one at each wheel, AND on top of the diff??

 

That's correct.

 

Then, if every code relates to the left rear speed sensor, replacing that would be a good first step.