Component Tests and General Diagnostics

Checking the supply voltage/ground terminal

Checking the power supply
Check the power supply cable from the battery to the control module. Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse.

Take readings between:
- Combustion preheater module (CPM) 2 pin external connector #1 and ground. The voltage must be battery voltage.
- Combustion preheater module (CPM) 12 pin connector #3 and ground. The voltage must be battery voltage.

Checking the ground terminal
Check the ground lead between control module and ground terminal. Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation.

Take readings between:
- Combustion preheater module (CPM) 2 pin external connector #2 and ground terminal. The resistance must be less than 1 ohms.
- Combustion preheater module (CPM) 12 pin connector #4 and ground terminal. The resistance must be less than 1 ohms.
Remedy as necessary.

Other information
- Signal specification Pinout Values and Diagnostic Parameters
- See the relevant wiring diagram for information about circuits and ground terminals in the bodywork.
- Checking wiring and terminals Checking Wiring and Terminals
- Component specification [1][2]Auxiliary Cabin Heater









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