davekt

On the EGR Mixer pipe above the intake mainfold there are 2 sensors, one is onstalled vertically and the other one is somewhat horizontal, it is the same part number as the intake manifold temperature sensor, try plugging in a new sensor without installing it. There is no diagnostics or fault code for this sensor and usually the only way to know if it is bad is the engine fan stays engaged all the time.

Check the roof harness connector located at the left A Post area, sometimes the windshield will leak and cause the terminals to corrode.

Take a look at the vents on the batteries, they should be facing inboard towards the frame rail. When the highway line was moved to NRV hey changed the way Mack installed the batteries and put the vents facing out. Then with the bouncing of the trucks the acid would get into the vents run out, especially on the right side.

NO!!!!!

A 6-4 Code indicate loss of communications between the VECU(Vechile Electronic Control Unit) and the EECU (Engine Electronic Control Unit). If you disconnect the ABS ECU and measure the resistance across the yellow and green wires (J1939 High and Low) you should have 60 Ohms. Make certian the key is off! if you have 120 Ohms the VECU is not seeing the EECU or vise versa. Start at the Bulkhead connector and measure the resistance towards the VECU you should have 102 Ohms, then towards the EECU you should have 120 Ohms. the ECU's must be connected. One side or the other should have 0 Ohms if you are getting this code OR the VECU and EECU are not compatable because one os off another truck or has later Software file than the other. Mack Electrical Man.

The main reason coolant gets into the EECU connector is because the Coolant Level Sensor is leaking (because of over torquing the sensor) and the harness acts like a "Garden Hose" the coolant Expansion tank is under pressure usually around 16psi and it pushes the coolant thru the wire insulation to the EECU(Engine Electronic Control Module). There is a "Anti Wicking Jumper Harness just for this condition. Reference Service Bulletin SB273009 Dated 12/16/2005 SB__273_009_Coolant_Level_Sensor_Anti_Capillary_Jumper_Harness__Dec__16_2005_.pdf