I have a 2008 granite with a 10 speed split trans. While driving down the road the speedometer will drop to zero and the engine RPM is limited to 1200-14500 RPM. When this occurs I loose the jake brake as well. I have contacted two Mack Dealers and was told to check the ABS sensors and the speed sensor on the back of the trans. I have since replaced the 4 ABS sensors the speed sensor twice. I chased the wiring harness and plugs for continuity and all seems as it should be. I was going to replace the ABS ECM behind the dash. Am I correct in thinking it could be bad? I was advised if the ABS ECM thinks that it has two bad sensors on the same axel it will limit the throttle, I was also advised the speed sensor runs into the ABS ECM which is my thinking that could be bad.
Please Help