2017 Mack MP8 engine, active P113F12-Buffered Idle Validation Switch wire, circuit short to battery. Guided diagnostics had me verify voltage at VECU B17, should be less than 1volt. Found 3.15 volts. Tested harness between VECU and ECU, found no shorts to ground or wire to wire short. B19 does show 12v, A23 shows 12v when pedal is depressed. Cut B17 between VECU and ECU, source of 3.15 is from the VECU and not the ECU side.


This is my current headache the last 2 days.

So the VECU has gone bad?

We swapped VECU'* from a sister truck, same thing.

Does it change state based on whether it is connected or not?

Is it supposed to change voltage based on other circumstances and/or inputs?