i have a 99 expedition 5.4L the ECT (engine coolant temp.) sensor is not sending a signal and i need to change it .. my question is can anyone tell me where it's located ?? i have already changed the CHT (cylinder head temp.) sensor , all the books and people i have referred too all are dead ends .. (behind the alternator , in thermostat housing , and in driver head by the exhaust manifold ) all are dead ends .. can anyone help me find the sensor ??? dealer tells me they will locate it for $250 dollars and that's pathetic highway robbery .. do to the sensor telling ECU the engines cold it has increased my fuel consumption to raise the engine to its operating temp. a difference from 18/19 MPG to 9.2/9.7 MPG .. if this year model doesn't have a ECT can someone tell how this thing reads engine temp. and how to repair it please ..??

 

Your engine doesn't have an ECT.

 

if it doesn't have a ECT how does it get a temp reading for the ECU ? also when i do a code check at autozone or orielly's it keeps saying high voltage on ECT .. do you have any clue of how this is possible , i have already changed the CHT (cylinder head temp.) sensor .. do you have any advise on this matter ??

 

In your engine's system, the ECT value is inferred by the PCM from the CHT input.

Since you never posted specific fault codes, it's not possible to comment on them.

 

P1289 --- CHT sensor out of ranger-high input
P0128 --- coolant temp. always low

coolant level is full , new thermo. , new CHT sensor , and engine not overheating

 

P0128 should not be possible on your particular vehicle.

P1289 indicates a circuit fault related to the CHT sensor. It does NOT (necessarily) mean the CHT sensor is bad.

Does your scan tool allow you to read individual PIDS? If so, check the CHT PID and see what the PCM is reading.

 

well i disconnected the CHT from the harness and my temp. gauge still done the same thing .. shows its not the CHT sensor , does anyone have any ideas ??
PLEASE .....

 

Check the wiring harness for both leads to the CHT back to the PCM for continuity.

 

i don't know the wire diagram so i don't know what wire to check at the ECM , i do know the wire on the CHT is yellow .. do you have a schismatic of the wiring harness for this truck ??

 

did you ever figure your problem out? Im in the same boat. Got a ford f150 2005 5.4L

 

wire white with lite green stripe from PCM to the CHT was broke somewhere in the insulation .. So i replaced the wire at the PCM and ran it directly to the CHT sensor .. Then waahlaa all good to go , and temp. perfectly fine now ..

 

Hey thanks Tinytoon...did you happen to have issues with the A/C at that time? I am getting a diagnostic from ford tomorrow morning. The guy told me it would be $50.00 for A/C diagnostic. I just hope its not the PCM. I dont know how it would have gone bad that fast. Is running that wire to the CHT a simple fix? I dont really think its something i could do.

 

with the PCM reading Temp. is to high or to low it will not let anything that will affect the temp. run till problem is fixed .. i had same prob with mine till i rewired the CHT sensor ..

 

Hey Tiny, it looks like it could be the same problem you were having. I had ford do a dianostic on it, and they told me it was the wiring harness from the CHT sensor to the computer. Does that sound right? They did not say anything about the PCM being bad or anything. Only thing is they were trying to charge me $800 bux for all that. I can definitely get that done at a cheaper rate. I sure hope this is the problem! Harness is only 20 bux, and even though i replaced the sensor already, im goign to throw a new one in it again with the new harness and see what happens!

 

I ahve a 2006 king ranch expedition im getting codes p1000 and p1289 i replaced the cylinder head temperature sensor twice and the harness once i think its something with the pcm but have no.clue how to fix it or run the wire. Can u please help and let me know if its something hard to do also ford was selling me a engine coolant temp sensor where is that located and or do.i even need it?????