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My check engine light came on yesterday evening. Code P0119: Engine coolant temperature circuit intermittent/erratic. The AC starts out cold and then starts blowing hot air. Not sure what is wrong and would appreciate any guidance.
 

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Could be your Engine Coolant Temp Sensor.
Might be easier if we knew what year, model, and engine you have.
 

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Huh! I don’t even *see* that code in my 2011 Helm Manual! Only goes up to P0118. Must’ve been added later on?

All I see is codes P0116-P0118 and they’re all Engine Coolant Temperature Sensor “Performance” or “Circuit Low/High Voltage”. The solution for these codes is either replace the Sensor or replace the ECM (computer).

I’m not sure how a bad ECT could affect the A/C ... unless it’s somehow causing the air blend door to change states ... like maybe it thinks the engine is getting hot and so it turns on the heat to try to bleed some of it off through the heater core
Never heard of that, though ...

UPDATE: bigb12359 posted the A/C answer below ... the ECM just shuts it OFF!
 

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The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. Theengine control module (ECM) supplies 5 V to the ECT sensor signal circuit and a ground for the low reference circuit. Thisdiagnostic checks for an open, short to ground or an intermittent circuit condition between the ECM and ECT sensor.
Conditions for Running the DTCP0117 •The ignition is ON.
OR

•The engine is running for greater than 10 s.
•This DTC runs continuously within the enabling conditions.
P0118 •The ignition is ON.
OR

•The engine is running for greater than 10 s.
OR

•The engine run time is less than 10 s when the IAT is warmer than –7°C (19°F).
•This DTC runs continuously within the enabling conditions.
P0119 •No active DTCs set.
•The ignition is ON.
•This DTC runs continuously within the enabling conditions.
Conditions for Setting the DTC
P0117

The ECM detects that the ECT is warmer than 149°C (300°F) for greater than 5 s.


P0118

The ECM detects that the ECT is colder than −39°C (−38°F) for greater than 5 s.


P0119

The ECM detects that the ECT is intermittent or has abruptly changed for greater than 3 seconds.

Action Taken When the DTC Sets•DTC P0117, P0118 and P0119 are Type B DTCs.
•The cooling fans will be commanded ON.
•The Engine Coolant Temperature Gauge is inoperative.
•The AC compressor will be commanded OFF.
 

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I’m not sure how a bad ECT could affect the A/C ...
Looks like your answer is in the last line of bigb12359's post.

P0119 in the 2014 Repair Manual is for "Engine Coolant Temp (ECT) Sensor Circuit Intermittent".
My information is for the 3.6L V-6.
I wonder what engine the OP has....
 

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I’m not sure how a bad ECT could affect the A/C ...
Looks like your answer is in the last line of bigb12359's post.

P0119 in the 2014 Repair Manual is for "Engine Coolant Temp (ECT) Sensor Circuit Intermittent".
LOL! I was editing my post above as you were entering yours! I guess on my 2011, though, it won’t be shutting the A/C OFF.

Turning off the A/C is to generate less heat in the engine compartment??

Might be a good idea to post a message requesting you to turn on the heat - in case you’ve got a high temp condition the sensor may not be properly detecting.
 
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