Hello everyone

I've got a 2008 F150 lariat with a procharger sc which I have been facing some troubles with lately.

The problem occured right after I was off-roading the other day (sand dunes) everything was running smoothly up until I left the desert.

While I was driving I relised that my temp.gauge have stopped opperating, I got a code of P1289 (CHT) cylinder head temp sensor, I also relised that my AC is not cooling, the car had no power at all also and have become extreamly slow.

Here is what I have done so far:

I have replaced the CHT sensor with a new one and still the same problem

I went to visit an electrition to check all the electrical grounds and all sorts of wiring and they all seem to be fine, another dead end

I thought it could be the PCM that is broken and not sending the right voltages or so, so I got another F150(diffrent car same specs and model) PCM to test on both PCM's the problems still occured

Thought could be the alternator, also another dead end.

Basicly what is happening is electricity doesn't seem to be reaching the CHT sensor, causing it not to work; it is definetly not reaching the AC compressor due to the computer not being able to send signal to the ac relay switch box, and many other sensors that are not opperating correctly however they are not throwing any codes but im quite sure the sensors are not working as intended which is causing the great powerloss

I would like to mention also that the car would take 2 or 3 seconds longer during ignition to run, the fuel consumption has also increased dramaticly.

any help any suggestions would be GREATLY appreciated for I have reached a dead end at every route I've taken

 

I'm having the same issues and am pulling my hair out! What did you find out?

 

Hehe luckily I was notified by mail :P

Anyhow, I have taken my truck to a garage to perform a full electrical check up on sensors and wires manually, and as I recall the electrician said there was an electric leak from a damaged wire causing the PCM to totally malfunction.

What they did is repair the wires and replace the CHT sensor and it was back to normal again! However maybe in your case it really is just a sensor replacement issue, its not a complicated fix but you will require to remove the intake manifold unless you could provide a custom made tool to remove the censor and replace. I assume your engine temp. gauge is down correct?

 

Thanks for the reply!! It was a long shot that you would get notified but your answer is what I was leaning toward as the issue.

The issue is exactly the same as yours. I start the engine and within a few seconds the water temp gauge goes down, the audible and check gauge indicator comes on and the AC won't work.

I checked the CHT sensor and it is fine. I than checked the wires via ohm meter from the CHT to the PCM and looks like an open circuit. In order to physically trace the wires I would have to remove the intake and I'm not planning on doing that. So based on your reply I'll just run new wires from the CHT to the PCM. Hopefully it is just these wires damaged and not anything else in the wiring harness.

Thanks again!

 

RESOLVED!!!!

Replaced both wires to the CHT Sensor. Spliced one into wire at PIN 58 and cut wire at PIN 41 and attached new wire.
NOTE: Did not change CHT sensor at this time and did not have to remove intake to get to the connector.

AC works again!!
Gauge reads correctly!

Thanks for your assistance in resolving this issue.

 

I'm glad it was helpful information, this was truly one issue that had me pulling my hair out haha, enjoy the ride

 

I have the same exact issue on my 2008 F-150. It didn't crop up until after I changed my fuel pump, but, I figure this would be a good as start as any. Any chance you have pictures of the CHT sensor and/or where you accomplished the splice? I can't seem to locate the harness or the sensor. If not, perhaps something like...while viewing the motor from the front of the vehicle, on the right hand side, just underneath the air cleaner, etc, etc.

Any assistance would be greatly appreciated!

Rich in Fort Worth.

 

Is this the CHT sensor? The harness appears missing???

 

Moved alternator to the side and was able to reach in and disconnect the electrical connector. Removed harness by reaching towards the rear of the manifold and pulling the harness which was lying in the valley. Stoked I didn't have to pull the manifold off! Oh yeah...looks like something gnawed away at the wires and plug. Dang varmits!

 

That's the one. I just cut the connector off and spliced new wires onto it. The other end I connected directly to the PCM splicing one wire into PIN 58 (do not cut but splice into as this is used for multiple sensors) and cut and replacing the other wire going into PIN 41