I've been having my ABS light on the dashboard continuously 'ON' on my Impreza 2005. I realized today that the light goes OFF when reversing. My mechanic says that I should replace the rear wheels speed sensors. Anyone who has experienced this?

read the code rather than guess.

if the ABS light is on then it's telling you there's a store code which usually tells you what the problem is as well.

 

can also try cleaning off speed sensors first

I checked with the troubleshooter & it indicates that I have a problem on the rear wheel sensors. Didnt take down the code

the sensors were also cleaned

I checked with the troubleshooter & it indicates that I have a problem on the rear wheel sensors. Didnt take down the code

 

replace whichever sensor is failed is where i'd start. 

 

there are tests in the FSM to verify if the circuit is good or the sensor is bad if you don't want to guess.  FSM information is available all over the internet with some plugging around.