7-5 fault code on dash

[TorresTransport]

Just got a 7-5 fault code on my dash, I've got a 2005 CHN613 with a E-7 427 ASET ...everything worked fine obe day, the next day it had nothing, no lights, no accessories, no voltage and then from one moment to another I had a 9-2 code on the dash and everything came to life. What is the cause and what should I be looking for to correct the fault?

[turckster]

The 7-5 fault is for vecu input voltage, 9-2 is power reset without key switch. Basically, there is a loss of voltage while the key is still in the on position. The usual culprit is bad battery connections or bad batteries. Other areas to check - bad ground connections at cab/chassis, ground relay or its connections.

From Mack Information System:

7-5 fault:

Failure Mode Identifier (FMI): 0 (Valid but Above Normal), 1 (Valid but Below Normal)

Parameter Identification (PID): 167, 168

Message Identification (MID): 142

Circuit Description: The Vehicle Electronic Control Unit (VECU) receives and monitors vehicle system voltage at connector J3 pin 16. Thresholds for battery voltage (engine not running) and alternator voltage (engine running) can be programmed in the Customer Data area of the VECU.

Location: The Vehicle Electronic Control Unit is typically located in the cab, behind the right side dash panel.

Code Setting Conditions: Code 7-5 will set with a PID of 168 if the Vehicle Electronic Control Unit (VECU) senses that system voltage to the module has dropped to less than the programmed threshold for 10 seconds with the engine not running. Code 7-5 will set with a PID of 167 if the Vehicle Electronic Control Unit (VECU) senses that system voltage to the module is not between the programmed limits for 10 seconds with the engine running. If the system voltage returns to normal for 1 second, code 7-5 will become inactive.

9-2 fault:

Failure Mode Identifier (FMI): 4 (Special Instructions)

Parameter Identification (PID): S254

Message Identification (MID): 128/142

Circuit Description: Switched power is supplied to the Vehicle Electronic Control Unit (VECU) through connector J3, pin 17. The VECU ground is provided at connector J3, pin 18. Switched power is supplied to the Engine Electronic Control Unit (EECU) through connector J1, pins 2, 3, and 5. The EECU ground is provided through connector J1, pins 4, 7, and 8.

Code Setting Conditions: The Electronic Malfunction Lamp (EML) will illuminate and code 9-2 will set with MID 142 if the Vehicle Electronic Control Unit (VECU) senses a loss of battery power without the key switch being turned off. The Electronic Malfunction Lamp (EML) will illuminate and code 9-2 will set with MID 128 if the Engine Electronic Control Unit (EECU) senses a loss of switched power without the key switch being turned off. Code 9-2 generally indicates a major vehicle power failure.

If code 9-2 is logged, check the following components for corrosion, loose terminals, and/or poor connections:

• Batteries

• Starter Motor

• Engine Ground

• Ground Circuit Breaker

• Left and Right Dashboard Grounds

• Power Relays

• Engine Electronic Control Unit (EECU) Fuse or Circuit Breaker Connections (MID 128)

• Engine Power Distribution Module (EPDM) Connectors (MID 128)

• Vehicle Interface Connector (MID 128)

• Vehicle Electronic Control Unit (VECU) Fuse or Circuit Breaker Connections (MID 142)

Clean, repair or replace as necessary.

To clear code 9-2, turn the key switch ON, turn the key switch OFF for 6 seconds, then turn the key switch back ON. The code will clear in several seconds.