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Caterpillar C9 Engine PTO Engine Shutdown Switch Voltage Low

Caterpillar C9 engine PID 186-4 PTO engine shutdown switch voltage low solution.

Caterpillar C9 Engine

Caterpillar CAT ET 2023C

CAT Comm Adapter 3


A short to ground exists in the wiring for the PTO engine shutdown switch. The parameter “PTO Engine Shutdown Switch” must be programmed to “J1/P1:7” or “J1/P1:23”.



If the vehicle speed is not equal to zero, or if there are active vehicle speed faults, the engine will go to low idle. The engine will not shut down when the vehicle speed falls to zero. When the PTO engine shutdown switch is pressed, a 186-14 will become active. The code will stay active until the engine shuts down. When the engine shuts down, the code will be loggged.


Possible Causes:

1) ECM Connection/Harness

2) PTO Shutdown Switch Failure

3) ECM Failure

4) Wiring between PTO shutdown switch and ECM