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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4570
Experience:  Owner at DJ Wilson
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I have a 2007 peterbilt vin#751984 The low coolant light

Customer Question

Hello
I have a 2007 peterbilt vin#751984
The low coolant light won't turn off.
I replaced sensor.
Submitted: 10 months ago.
Category: Medium and Heavy Trucks
Expert:  Daniel Wilson replied 10 months ago.

Hi my name is***** will be glad to help. What is the chassis model and your engine make and model? Check the harness between the sensor and ECM for damaged wiring and connector pins. I can help with some schematics if necessary once I have the engine and chassis information. Let me know

Expert:  Daniel Wilson replied 10 months ago.

If the coolant level is full and the sensor is new, the problem is most likely in the wiring between the sensor and ECM.

Customer: replied 10 months ago.
389 peterbilt with a isx cummins
Customer: replied 10 months ago.
How much voltage should be going to the sensor?
Expert:  Daniel Wilson replied 10 months ago.

Sensor voltage for all sensors will be a 5 volt signal from the ECM and then the ECM reads return voltage

Customer: replied 10 months ago.
Ok
It has 5 volts on 1 of the wires.
Expert:  Daniel Wilson replied 10 months ago.

click on this link for your diagram and ECM pin identification

Expert:  Daniel Wilson replied 10 months ago.

Pin 32 is the return on the OEM connector

Customer: replied 10 months ago.
Is that the black connector?
Expert:  Daniel Wilson replied 10 months ago.

Here are the Connector locations

Expert:  Daniel Wilson replied 10 months ago.

Furthest to the Right facing the ECM ports

Customer: replied 10 months ago.
do I test the pin on the ecm or the connector?
Customer: replied 10 months ago.
I tested pin 32 on the connector and there's no contact.
Expert:  Daniel Wilson replied 10 months ago.

Thanks for the update, No continuity? so you have an open circuit or wire between the sensor and the ECM? If so make a test wire and run a test wire to see if the code goes away.

Customer: replied 10 months ago.
Ok
Where would I run a test wire to?
Where would I tie it in to.?
Does the return wire go direct to the ecm or does it have a fuse in between?
Expert:  Daniel Wilson replied 10 months ago.

Read the schematic I posted. it give the pins for the return of the sensor to the pin 32... see if the fault goes away.

Expert:  Daniel Wilson replied 10 months ago.

It shows another connector in the circuit as well going through pins A and B on that connector too.

Expert:  Daniel Wilson replied 10 months ago.

Shows Return is terminal A from the sensor black and white according to the schematic. Go from A from the sensor to 32 on the ECM

Customer: replied 10 months ago.
I did that and there's no response.
Expert:  Daniel Wilson replied 10 months ago.

Sounds like a problem with the ECM . Try having the software updated and reflashed to see if your problem resolves. Let me know.

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