Cylinder head Temperature Sensor
 

I have a 4.6L which has had the CHT Sensor replaced once about a year ago. At the time I was experiencing a real bad miss at any part to high vacuum operation, e.g. pedal anywhere beyond idle. I replaced the plugs and wires at that time, didn't fix it, so the dealer replaced the CHT Sensor. Recently I experienced a similar situation where the truck was missing like crazy. I took it to a guy who read the code and sure enough #1 and #4 misfire and a low voltage on the CHT. The #1 and #4 misfire make sense because the CHT shuts off injectors on each bank while the computer thinks the truck is overheating (CHT voltage signal). #1 and #4 are both on the same bank. I replaced the plugs and cleared the code but it still misses just off idle and at low speed. Bottom line... Does anyone know how to replace the CHT without a complete top end tear down. The CHT is UNDER the intake manifold. I would prefer to not go to the dealer again.
Thanks
-tom

You can replace it with out pulling the intake.
Just remove the alternator and use a crow foot wrench with a swivel adapter. It's a hassle, but it can be done.

On a few trucks I've had to relocate the sensor to the right side head.(per Ford) For this, you do have to pull the intake and extend the CHT harness.

Thanks for the quick reply. What is the purpose of relocating the sensor? Is there an issue with the current location? Ford certainly did not make the job easy...
Thanks
-tom

One other question... What size wrench does the CHT sensor take? I need to buy the wrench.
Thanks again
-tom

Man, I don't remember. Snap-On has the wrench I used.
It is the round looking wrench. You can't use a regular crow foot because there is a casting knob on the head that will prevent the wrench from turning.
I've even broke the connector off one sensor and then used a regular socket to remove it. I can find out the details on the wrench tomorrow.

The reason for moving the sensor was for erratic temp guage operation. If I remember correctly, the casting where the sensor screws in may be different and the sensor can't detect the coolant temp efficiently.

you can remove the CHT sensor without removing the intake.

wrench size
 

Disconnect battery cables and remove alternator to access the sensor.
Get the wrench from snap-on tools. It's a 19mm 12 point deep crowfoot wrench ( the rounded body type). Use a 3/8 ball type swivel with a 12" extention & ratchet. Use a long thin scewdriver to release the push-in tab on the harness plug and pull from switch. Make sure the highest part of the wrench is up and the swivel pin is locked in the wrench pin-lock hole as you don't want the wrench coming off the swivel. You need the 12 point because the turning radius is small but very doable. Once cracked loose just use the extention with wrench and your hand to unscrew. I then used my two fingers to unscrew all the way and remove. To reinstall the new one you have to hold the switch with your two fingers and guide it to the hole. Once in just start turning clockwise until the threads catch and turn it in as far as you can with your fingers. Then just snug it up with the wrench (do not over tighten). There is no coolant as the hole bore is a blind dead end. I believe the thread cut on the new switch is the exact same as the old one so the harness plug faces the same way. Mine installed the same as to access the push pin if needed. The reason I replaced mine was I had a false pcm reading for cylinder head overheat which spiked my temperature gauge, oil lite on, check engine lite on and it went to safe mode (4 cylinder air pump). I had no coolant leaks, oil pressure perfect and engine didn't overheat. Also when all this started was in the winter and I had trouble starting it cold. This was caused from the CHT sensor giving the computer a false engine temp of 70F instead of -20F causing the IAC to allow too much air on cold start. Anyway the truck has run great ever since (touch wood).

Good Luck, Guage

This is a 10 year old thread...............................I would assume the OP has fixed it - if he even still has the truck...........

Wow, quite the resurrection!

But to add to data base...... couple things. Iirc, 99' and later (pi heads) had no cht and the head temp is inferred from the coolant temp.
Pic of one I had to add to a non-pi Ford Racing head. https://www.f150online.com/forums/me...truck-head.jpg

Other way around - coolant temp is inferred from head temp sensor.

my mistake
 

Had no idea that post was that old as I am new to this forum and didn't see a date that verified the post. Just to verify and help anybody else with that issue the sensor (CHT) or thermistor goes into a blind hole and is not in contact with coolant just ambient head temperature. The Ford manual says the intake must be removed to replace it. That's a customer ripoff of 4 hrs labor as I'm sure by now there has to be at least one Ford mechanic that has figured it out.
By the way my truck is a 2000 F150 XLT Flareside 4x4 with a 4.6L Windsor. Ford went from a coolant temp sensor to a cylinder head sensor in 2000 re a specific build date.
Regards to all,
Guage