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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8346
Experience:  I am ASE Master Truck Certified.
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6nz catepillar where dies ecm read water temperature from

Customer Question

6nz catepillar where dies ecm read water temperature from what sensor readings are changing in cat et when running when off numbers are stable
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 2 months ago.

Thanks for asking your question. I will try and help you out.

The ECM has a coolant temp sensor located in the front of the thermostat housing. This is how the ECM reads engine coolant temperature.

Please reply back if you need more help or have more questions. I am happy to assist.

Customer: replied 2 months ago.
Even when unplugged its still reading temperature
Customer: replied 2 months ago.
It changes uo and down still
Expert:  Cat Man replied 2 months ago.

Yes it will continue to show a reading. That is called a default reading. When unplugged the coolant temp will read 194 degrees F, the ECM will also cut the fan on.

Does it change up and down with it unplugged? or when plugged up?

Customer: replied 2 months ago.
No it reads 163 dies not show a fault like others
Customer: replied 2 months ago.
Changes when engine running
Customer: replied 2 months ago.
Up and diwn rapidly when off stays
Expert:  Cat Man replied 2 months ago.

Thanks for the information.

It sounds like you have a problem in the wiring harness or ECM. I would try pulling the coolant wires from the ECM. This would be pins 32 and 18 in the 70 pin connector. I have seen faulty wiring harness do this before on 2 wire temp sensors.

Customer: replied 2 months ago.
Shoud i have 5volts on 1 and ground on other so i can test let me know thanks
Expert:  Cat Man replied 2 months ago.

Pin 2 is the ground. Pin 1 is the signal wire. If you test the wire it will have 5 volts on it. But the is s simple resister, you most likely have a wire in the harness touching something its not suppose to.

Customer: replied 2 months ago.
What temperature should ecm shut engine down at high water temperature
Expert:  Cat Man replied 2 months ago.
227 degrees F
Customer: replied 2 months ago.
If it dontbaand waits until two thirty seven how do i adjust
Expert:  Cat Man replied 2 months ago.
The shut down temp is not adjustable.

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