Mack CXN 612 CERG AC-427 (2005)

[waterpipe]

We are working on the above truck, we have two with the same fault.

Not very familiar with these trucks...have no software to access the ecu...

They are blinking a 4   5  code, this apparently means a fault in the VGT loop.

The harness from the vgt sensor to the ecu only has 3 wires,  they do not appear to be shorted to ground or open or high resistance,  the harness looks

good on the ohm meter after isolating both the ends of the harness and measuring....

I removed the top of the rectangular actuator sensor module to gain access to the 4 pins, in the sensor,  1- signal,  2 signal, 3 + 5 VDC and 4 ground to ECM.

 

At rest (engine off) the actuator shaft to the turbo is in the up position and the voltage  reads 0.6 volts,  when the engine is idling the actuator rod moves

down with the air pressure and the signal voltage is 2.0 volts....(5 VDC supply to the sensor module is good).

I notice on both trucks there is only 3 wires in the harness,  the pin 2 of the sensor plug is not used... therefore the signal is sent to the ECU via pin

1 and ground (Pin4)..

I have no schematic for the ECU and its associated circuits (sensors) so I am pretty well out of ideas...no software etc..

The sensor shown in the picture is not the one in the truck, this one was taken off another truck and would seem to have been subject to overheating..

The pin count goes 4, 3, 2 ,1 from left to right in the picture. (output connector to ecu..)

Any ideas would be very welcome... Thanks

Where does one obtain MACK V-MAC III ,  looks like a 9 pin OBD socket on the truck,  also the right comm adapter for these truck, so we can hook up

the laptop.??? Dealer here is very small and really expensive....