How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Daniel Wilson Your Own Question
Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4872
Experience:  Owner at DJ Wilson
65405794
Type Your Medium and Heavy Trucks Question Here...
Daniel Wilson is online now
A new question is answered every 9 seconds

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: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Daniel Wilson replied 1 year 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 1 year 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 1 year ago.
389 peterbilt with a isx cummins
Customer: replied 1 year ago.
How much voltage should be going to the sensor?
Expert:  Daniel Wilson replied 1 year ago.

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

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

click on this link for your diagram and ECM pin identification

Expert:  Daniel Wilson replied 1 year ago.

Pin 32 is the return on the OEM connector

Customer: replied 1 year ago.
Is that the black connector?
Expert:  Daniel Wilson replied 1 year ago.

Here are the Connector locations

Expert:  Daniel Wilson replied 1 year ago.

Furthest to the Right facing the ECM ports

Customer: replied 1 year ago.
do I test the pin on the ecm or the connector?
Customer: replied 1 year ago.
I tested pin 32 on the connector and there's no contact.
Expert:  Daniel Wilson replied 1 year 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 1 year 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 1 year 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 1 year ago.

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

Expert:  Daniel Wilson replied 1 year 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 1 year ago.
I did that and there's no response.
Expert:  Daniel Wilson replied 1 year ago.

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

Related Medium and Heavy Trucks Questions