P1299 Limp Mode, No Overheating. How do I test the signal wire?

[syasar]

So I have been getting P1299 “Cylinder Head Temperature Sensor Detected Engine Overheating Condition” for a few years now. It has been on and off, it bothers for a few weeks and disappears.

The car will go into limp mode, without it even warming up. Most times it goes off few minutes after starting the car, and the engine coolant would be around 70 degrees.

I’m assuming it's something electrical, I have already replaced the cylinder head temperature sensor. And take it to the dealership twice.

Last time they told me it was an issue around the coolant level sensor, which it can’t be as my problem started before that was even installed (during the recall). Really not sold its that, they basically want me to replace the piping assembly around the sensor.

Now I was wondering maybe there is short in the harness, however how do I go about testing the signal wire from the CHT sensor to the ECU without damaging my ECU?

I have a signal led light and multimeter.


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[TyphoonFiST]

So I have been getting P1299 “Cylinder Head Temperature Sensor Detected Engine Overheating Condition” for a few years now. It has been on and off, it bothers for a few weeks and disappears.

The car will go into limp mode, without it even warming up. Most times it goes off few minutes after starting the car, and the engine coolant would be around 70 degrees.

I’m assuming it's something electrical, I have already replaced the cylinder head temperature sensor. And take it to the dealership twice.

Last time they told me it was an issue around the coolant level sensor, which it can’t be as my problem started before that was even installed (during the recall). Really not sold its that, they basically want me to replace the piping assembly around the sensor.

Now I was wondering maybe there is short in the harness, however how do I go about testing the signal wire from the CHT sensor to the ECU without damaging my ECU?

I have a signal led light and multimeter.


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What year is it?

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[syasar]

What year is it?

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2014


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[TyphoonFiST]

2014


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Isn't that the year where they installed the Recall stuff and the sensor in the head was a part of it? Once a recall ...always a recall if it was one. So if that same issue with the recall happens....fomoco should be on the hook.

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[syasar]

Isn't that the year where they installed the Recall stuff and the sensor in the head was a part of it? Once a recall ...always a recall if it was one. So if that same issue with the recall happens....fomoco should be on the hook.

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Well based on my research, and looking at the recall documents. It's a coolant level sensor they added, around the reservoir assembly.

When I went to dealer last they wanted to change the pump assembly leading to the reservoir which was not part of the recall and would be out of pocket for me. It make no sense that would be the issue.


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[BlueSt fiesta!]

Last weekend I just got an inspection, went to fill up with gas and noticed when I started my car back up, temp lights started climbing and it went into limp mode. I checked the engine code and 1299 came up. It comes on immediately at start up, car sounds fine at idle, no smoke, coolant isn’t milky. I am thinking it has to be sensor, then thermostat and then a radiator flush. But I am worried that some has to be getting hot, to smoke the sensor. I did see on utube where you can check the coolant temp thru the display but it is reading 126C at start up which I know is not accurate. You know these would run better if there is a way to keep them cooler

 

[D1JL]

Sensors to check.
The coolant temp sensor is (always been) on the right rear top of the engine.
If you had the 17S09 recall done, the added coolant level sensor is behind the degas bottle.

 

[syasar]

So I got a test light and put it to the CHT sensor signal wire and the positive end of terminal. It showed ground on both the wires. does this mean there is a pathway to ground on signal wire that shouldn’t be present.


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[unknown.]

Was this ever fixed, if so can you explain how as I’m having the same issue

 

[93Kurtjr]

I was also curious to know if anyone figured this out?

 

[AMFGFL]

Wanted to revive this thread and let everyone know the fix.

TLDR: Use a code reader and erase the false P1299 code

I used this: https://www.amazon.com/gp/aw/d/B01G5EA74I?ref=ppx_pt2_mob_b_prod_image

You could also ask Autozone or advanced auto parts to clear the code.

So I was installing a short shifter on the transmission linkage and had to remove the battery, battery case, disconnect ECU and remove, remove intake. Once everything was reinstalled it was saying the P1299 code even though we didn’t touch the Coolant system and there was enough coolant in the system and it wasn’t over heating. I would turn the car to power only (not turning car on) and the temp gauge would say it’s overheating. Everything was perfect before install so I knew there were no issues.

I thought it was bent pins on ECU on the install so I verified and it was good. CHT sensor was plugged in and wiring was good. Went to Advanced auto parts to read the code even though it wasn’t in limp mode. I asked them to clear the code, but they were jerks and didn’t do it. Then I ordered a code reader/code eraser on Amazon and it fixed it immediately. If you have FORscan on your phone and an OBD Bluetooth reader I read somewhere it worked for a Ford Fusion as well. I can imagine it would work with other Ford vehicles too