D12 Coolant Sensor

what a fault code? '07 D12 may be D12D ore D12F, there are ECT (coolant temp. sensor) and CLS (coolant level sensor). What sensor is bad? what a code in MID 128 XXX XXX format?

 

WTF???? this sensor reads yes ore no coolant!!!! it is a switch! S68.Pin EB23 on Engine ECM!!!

But there are trucks with A54 Coolant level control unit... but as I remember it is used on VN and FH with ISX only....

 

Mine is simaliar but doesn't shut the engine down unless, I'm empty on coolant. But does read low coolant on the readout until it get up to around 135 degrees. I replaced the sensor and it didn't change anything. Thankfully it goes out after warms up.

 

it depends on programming

 

Those type sensors short to ground through the liquid. The other type is a magnetic float switch with a reference signal to and from the ECM.

If you replace it and still have problems, then you have wire/connection issues. Like Pablo said, they either work or they don't. If you are getting anything else like works sometimes or it has to do this or that before the light goes out, you most likely have wire/connection issues.

Do you have a solid ground? Unplug the sensor and test the ground by putting the black probe of your meter to the black wire and the red probe to battery hot. You should have 12.0V. A corroded poor ground will read lower.

If that checks out, then you can suspect the ECM return wire. Check where the wire goes into the back of the connector. That's the most succeptable spot for one to corrode or the strand wire break. Check the pins in the connector. Next follow the wire out and see if it exposed and rubbing anywhere. It runs straight to the firewall pass through main harness. It should be a relatively short wire.

A float type coolant level switch sends a 5.0V reference signal from the ECM and the return wire should read 0.5V if everything is working correctly. You can backprobe the wires on them type switches.

If you have dirty coolant and a dirty tank, you need to do a flush and also clean the tank. The easiest way to clean the tank is remove it and fill it partially with water and Dawn detergent and shake the crap out of it. Then rinse it out good.

Flightline, yours sounds like you are just short a 1/2-1 gallon or so. The sight glass can be deceiving. When your truck warms up the coolant expands and your reservoir fills up more. That would explain the sensor not being submersed and then being submersed. Drop a stick or something in the tank to get the true level or crawl up there and look down in it.

I remember when my EGR cooler started going out and was eating coolant. The dealer told me not to put anymore coolant in, the reservoir was full. Not only that, they said nothing was wrong with the truck. I went straight back to our shop and had our mechanic check it. He put 5 gallons in it. Moral of the story is the sight glass is a piece of junk. Coolant gets trapped in it even if the tank is empty. The only way to trust it is to check it yourself.

 

Yeah, coolant is color marked and paint may stay on glass!!!!!

 

So where exactly is the sensor located???

 

I think i found it, its on the underside of the resevoir....