Fix P0119: Mechanic’s solutions that WORKED

The code P0119, which stands for “Engine Coolant Temperature Circuit Intermittent,” highlights an inconsistency in the engine coolant temperature sensor’s signal. It’s most commonly triggered by issues like faulty sensors, wiring concerns, or even erratic coolant levels.

P0119 quick overview

Meaning	P0119: Engine Coolant Temperature Circuit Intermittent
Is it serious?	Moderate. While the car may still run, it can lead to poor performance, increased fuel consumption, and possible engine damage if not addressed.
Possible causes	– Faulty engine coolant temperature sensor – Intermittent or damaged wiring/connectors in the sensor circuit – Erratic coolant levels (too high or too low) – Thermostat issues – Engine overheating
How to diagnose?	1. Check for any other related diagnostic trouble codes that might provide more insight. 2. Use a diagnostic scan tool to read the live data from the engine coolant temperature sensor. 3. Physically inspect the wiring and connectors of the sensor for any signs of damage or corrosion. 4. Monitor the coolant levels and condition. Refill or replace if needed. 6. Test the engine coolant temperature sensor’s resistance and compare it to manufacturer specifications. 7. Consider the vehicle’s repair history. If recent repairs were made (like in the cases mentioned), they could provide clues.

How to fix P0119 – learn from mechanics

I looked into P0119 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle Information:
2008 Ford Escape XLT 3.0L

Issue + Repair History:

• The customer reported AC issues coinciding with the Check Engine Light (CEL) coming on.
• Continuous memory codes for the Engine Coolant Temperature (ECT) sensor were P0117 (signal low) and P0119 (signal erratic).
• The vehicle nearly overheated according to the gauge, showing 230°F on the ECT, while actual measurements with an infrared thermometer showed about 201°F at the head.
• The Powertrain Control Module (PCM) triggered a high fan and shut off the AC when overheating symptoms were detected.
• Another shop had previously replaced the ECT sensor, but a new Ford ECT was installed to ensure quality.

Suggestions from the Community:

• Check for a bad thermostat.
• Clear the Diagnostic Trouble Codes (DTCs) and observe if they reset.
• Ensure no air pockets in the cooling system using a vacuum refilling tool.
• Verify cooling system basics such as proper flow, swapping thermostats, checking the cap’s relief pressure, and inspecting for possible head gasket issues.
• Consider the possibility of a bad cluster or a faulty temperature gauge.
• Investigate if the actual engine temperature is fluctuating, potentially from air pockets around the sensor or genuine overheating.

Final Fix:
The primary issue was with the water pump. Its plastic impeller had split open, leading to poor coolant circulation, especially at higher RPMs. This caused the coolant to boil, creating steam pockets around the ECT sensor when exiting the head. A new water pump was installed, the system was refilled, and the codes were cleared, resolving the issue.

Case #2: Chevrolet

Vehicle Information:
2014 Chevrolet Traverse LTZ 3.6L

Issue + Repair History:

• A few times a week upon startup, the AC did not produce cold air. Fans operated normally, but the AC light flashed, and only warm air was emitted through the vents. Sometimes, turning the key off and on resolved the issue, but not always.
• When the AC issue occurred, pressing the AC button made its light flash six times. Restarting the vehicle usually resolved the problem.
• The vehicle’s pressures were tested and found to be normal.
• Whenever the vehicle was at the technician’s location, it operated perfectly.

Suggestions from the Community:

• Check the outside air temperature sensor.
• Relearn the doors and confirm the compressor’s operation.
• If the AC light is flashing, it may have set a code, suggesting it could be due to a bad relay or intermittent connection to the relay/fuses.
• Monitor various parameters: evaporative temperature, high-side pressure sensor, ambient air temperature, etc. Factors like rough idle or battery voltage can inhibit AC operation.
• Check the pressure switch on the high-side line near the compressor. Ensure that the terminal retention cover is placed correctly.
• Consider possible issues with the AC clutch gap, as a wide gap might be a culprit.
• Ensure all temperature sensors are checked since inaccurate readings can inhibit AC operation.

Final Fix:
The vehicle had set an engine fault for P0119, which is related to the coolant temperature sensor. This sensor was replaced. The technician suspected that the vehicle was intermittently informing the AC system that the engine was too cold to allow the AC to operate. After the replacement, the AC failure issue was not encountered for 10 days.

Case #3: Hyundai

Vehicle Information:
2009 Hyundai Genesis 4.6 4.6L

Issue + Repair History:

• Problem: MIL (Malfunction Indicator Lamp) activated with DTC P0119; A/C not functional.
• Coolant level was low by 1 gallon.
• The owner observed a coolant smell when the engine was warm.
• Dirty coolant was found below the intake manifold.
• The thermostat housing cover appeared to have been replaced previously.

Suggestions from the Community:

• Perform a full shop air leak-down test on each cylinder to check for bubbles.
• Check the vehicle when cold for signs of rust or water streaking.
• Consider a temperature-related leak issue, possibly from water pump seals or hose clamps.
• Check the radiator cap; sometimes even new ones can be faulty.
• Use a fluorescent dye in the cooling system to locate the leak.
• Inspect seals around the water pump and consider the heater core as a potential leak source.

Final Fix:
The technician observed a trail of coolant at the heater inlet/outlet tubes’ O-ring end seals in the intake valley. New tube assemblies were purchased and installed, resolving the issue.

Case #4: BMW

Vehicle Information:
1999 BMW 740i 4.4L

Issue + Repair History:

• MIL (Malfunction Indicator Lamp) lights up, especially at full throttle.
• The vehicle had a faulty cam position sensor, which was replaced. After the replacement, codes appeared when the vehicle was at full throttle, and it went into failsafe mode.

Suggestions from the Community:

• One technician questioned the scan tool used and mentioned that the provided codes (P0117 and P0119) are generic OBDII codes associated with the coolant temperature.
• Another person clarified that the BMW system in use is ME 7.2, and that the given codes P0117 and P0119 relate to engine coolant temperature issues, not throttle potentiometer.

Final Fix:
The adaptations had to be cleared to realign the “fly by wire” system. After doing so, the vehicle functioned correctly.