Hi, thanks for taking the time to help. I currently own multiple 6.0 and 6.7 Power Strokes and am having a problem with my 2006 6.0. It will intermittently show temp drops to -40 usually while pulling a load or under boost. It will chime "check gauges" and fulliy engage clutch fan at the same time then go back to normal operating temps an fan opereration under no specific time line. The truck has 316,000 miles and has been ARP studded and egr deleted. Running reconditioned factory turbo with BD boost fooler installed. We have replaced radiator, clutch fan, ect sender, ecm, and traced ect wiring to ecm with zero resistance or interuppts. It will do it with or with out clutch fan and/or ect plugged in. ​​​​​​​Any thoughts?

 

-40 is the default reading when voltage drops to zero (ie a bad sensor).

 

[QUOTE=bismic;20621079]-40 is the default reading when voltage drops to zero (ie a bad sensor).[/QUOTE that's what I figured I'm on my third ssensor all with no change. Any thoughts on how engine load could effect sensor voltage?

 

You have a short in the wiring or connector then. Load is not going to impact the ECT reading ..........

If you don't see an obvious short in a harness, you may want to splice in a new connector.

AP0056 (Alliant Power)

 

So I guess my only other question then if the ECM doesn't see voltage from the ECT does it turn the the electric clutch fan on full blast?

 

IIRC it will make assumptions based on oil temperature

Why do you ask?
Is your fan on full blast?
What is your oil temperature?
What is your transmission temperature?

 

Fan turns on full clutch when I lose ECT voltage. Then turns off when ECT voltage/temp signal comes back.
OIl temp is constant 205-215.
Transmission temp 180-250 depending on load.

 

You might try the new connector, it is cheap.

EDIT (sorry for a few edits to match the manual) - Do you have a code for a bad ECT. If so what is the number P0117 or P0118?

The ECT sensor is a thermistor. It changes electrical resistance as temperature changes. Resistance in the thermistor decreases as temperature increases, and increases as temperature decreases. Thermistors work with a resistor that limits current in the ECM to form a voltage signal matched with a temperature value.

From the PC/ED manual:
If the PCM detects an "out-of-range" high or low, the PCM ignores the ECT signal and substitutes the EOT signal. If BOTH the EOT and ECT signals are "out-of-range", then the PCM assumes an engine coolant temperature of -29*F for starting, and 180*F for running.

Also from the manual - to read -40 degrees, there will be a resistance of 925,021 (+) ohms.

Maybe you have a PCM problem, because what you describe doesn't match what the manual seems to say.

Earlier I was thinking that maybe the v-reference is shorted to the signal return, but I am not completely sure that that failure would result in a reported -40 degrees. I suppose it is still worth checking. Several other things don;t quite "add up".

Another EDIT - what brand of ECT sensor did you install?

 

2 ECT were "Standard Ignition" 1 ECT was "Motorcraft" no change
Swapped PCM with #s matching. No change.
Swapped jnstrument cluster. No change.

 

Where did you purchase the motorcraft part?

 

ford dealership

 

I still think your harness and/or connector is shorted out.

 

Would you happen to have a part # for the connector? Ford cannot locate it.

 

You could try to unplug the ECT sensor and let the PCM default to the EOT reading. And also try to swap the sensors to confirm the sensor is not the issue.

 

I posted the connector part number in post #4.

Ford doesn't sell it.

Part # AP0056 (Alliant Power)

https://www.xtremediesel.com/alliant-2-wire-pigtail-ap0056

https://prosourcediesel.com/shop/brand/prosource-diesel/6-0l-6-4l-03-10-powerstroke-coolant-oil-intake-air-temperature-pigtail/