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

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#1
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

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#2
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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TyphoonFiST

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#4
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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OP
syasar
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Thread Starter #5
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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#6
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

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#7
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.
 


OP
syasar
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Thread Starter #8
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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