P0119 on 2016-2018 Lincoln MKX: Causes and Fixes for Intermittent Coolant Temp Sensor

What's Unique About the 2016-2018 Lincoln MKX

For the 2016-2018 Lincoln MKX, particularly models with the 2.7L V6 engine, this code is strongly linked to known wiring issues. Ford/Lincoln issued several Technical Service Bulletins (TSBs) highlighting that the ECT sensor connector may not be fully seated or that the wiring harness itself could be damaged. Specifically, TSB SSM 47791 points to potential damage in the wiring between main harness connectors C1016 and C1168. Furthermore, TSB SSM 48991 notes the ECT sensor wiring is bundled with the knock sensor harness, and a fault here can trigger multiple codes. This makes a thorough inspection of the wiring even more critical than on other vehicles, as the sensor itself may not be the root cause.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice 🎬 Watch: Common signs and symptoms of a failing ECT sensor.

• Check Engine Light (Malfunction Indicator Lamp or MIL) is on
• Wrench light may be illuminated
• Temperature gauge on the dashboard behaves erratically (swinging from cold to hot, or pegged on hot even when engine is cold)
• Engine cooling fans run constantly at high speed, even when the engine is cold
• Engine cooling fans do not turn on, leading to potential overheating
• Rough idling or engine hesitation
• Poor fuel economy
• Hard starting when the engine is warm
• Reduced engine power or 'limp mode'

Most Likely Causes

1. Poorly Seated or Damaged ECT Sensor Connector/Wiring 🔴 High Probability This is a documented issue for the 2.7L engine in this vehicle, as cited in TSBs SSM 48991, SSM 47791, and SSM 46906. The bulletins specifically mention a connector that is not fully seated or has damaged wiring, particularly between main harness connectors C1016 and C1168.
   How to confirm: Visually inspect the ECT sensor connector for looseness, corrosion on the pins, or any signs of damage to the wires leading to it. Wiggle the connector and harness while monitoring live data on a scan tool to see if the temperature reading fluctuates. Trace the harness and inspect for chafing, especially around the specified C1016 and C1168 connectors.
   Typical fix: Reseat the connector firmly until it clicks. If the main harness is damaged, it will require careful wire-by-wire repair. If only the pigtail connector is damaged, it will need to be replaced.
   Est. part cost: $20-$40 for a new pigtail connector if needed.
2. Faulty Engine Coolant Temperature (ECT) Sensor 🟡 Medium Probability The sensor is located deep in the engine 'V' under the intake manifold, where it is subjected to significant heat soak, which can contribute to failure over time. TSB SSM 48991 also lists sensor failure as a possible cause, recommending its replacement along with the knock sensor harness.
   How to confirm: Use a scan tool to watch the live ECT data. If the reading is erratic or clearly incorrect (e.g., reads -40°F on a warm engine) and the wiring is confirmed to be good, the sensor is likely faulty. You can also test the sensor's internal resistance with a multimeter; it should be between 2,000 and 3,000 ohms at room temperature (68°F/20°C).
   Typical fix: Replace the ECT sensor. This is a labor-intensive job as it requires removing the upper intake manifold to access the sensor's location in the engine valley.
   Est. part cost: $30-$60
3. Low or Contaminated Engine Coolant ⚪ Low Probability
   How to confirm: Check the coolant level in the reservoir. If it's low, air pockets can form in the system, causing the sensor to give erratic readings as it becomes exposed to air instead of coolant. Also, check the coolant for signs of rust or contamination.
   Typical fix: Top off the coolant to the correct level and bleed any air from the system. If the coolant is contaminated, a full system flush is required.
   Est. part cost: $20-$40 for a gallon of the correct coolant.

Rare But Worth Checking

• Faulty Thermostat: A thermostat that is stuck open or closed can cause strange temperature fluctuations, which might be misinterpreted by the PCM as a sensor circuit fault.
• Failing Powertrain Control Module (PCM): In very rare cases, the fault can be internal to the PCM, where it is unable to correctly interpret a good signal from the sensor. This should only be considered after all other possibilities have been exhausted.

Diagnosis Steps

1. Check the engine coolant level and condition. Ensure it is full and clean.
2. Connect an OBD-II scanner and view the live data for the Engine Coolant Temperature. Observe if the reading is erratic, nonsensical (e.g., -40°F), or doesn't change as the engine warms up.
3. Locate the ECT sensor on the 2.7L engine. It is buried deep in the engine 'V', underneath the intake manifold.
4. Carefully inspect the ECT sensor's electrical connector. Check if it is fully seated. Disconnect it and look for corrosion, bent pins, or moisture.
5. Inspect the wiring harness leading to the connector for any signs of chafing, melting, or breaks. Per TSB SSM 47791, pay special attention to the harness sections between connectors C1016 and C1168.
6. Test the circuit from the PCM. Disconnect the sensor. With the key on, one pin on the connector should have a 5-volt reference and the other should be a good ground. Jumpering the two pins together should cause the scan tool reading to go to its maximum temperature (e.g., >250°F), confirming the wiring to the PCM is intact.
7. If the wiring and circuit test good, test the sensor itself. With a multimeter, measure the resistance across the sensor's pins. It should be approximately 2,000-3,000 ohms at room temperature (20°C/68°F).
8. If the sensor tests bad or is the most likely cause after confirming good wiring, replace it. Be prepared for a labor-intensive job requiring removal of the intake manifold.
9. If the problem persists after replacing the sensor, the wiring harness has an intermittent fault that isn't visible, or in very rare cases, the PCM may be at fault.

Parts You'll Likely Need

• Engine Coolant Temperature (ECT) Sensor (OEM #DY1332 (Ford Base Part #: 12A648)) — This sensor provides the temperature reading to the PCM. It can fail internally, causing the intermittent signal that triggers P0119. TSB SSM 48991 recommends its replacement for this condition.
  Trusted brands: Motorcraft
  OEM price range: $30-$60
  Aftermarket price range: $15-$40
• ECT Sensor Connector Pigtail (OEM #WPT1263 (Verify application)) — If the plastic connector itself is broken or the terminals are damaged from arcing or corrosion, replacing the pigtail is necessary. However, note that TSBs point to the main harness as a common issue, not just the pigtail.
  Trusted brands: Motorcraft
  OEM price range: $20-$40
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0116 — Indicates ECT Sensor Circuit Range/Performance problem, often set along with intermittent codes.
• P0117 — Indicates ECT Sensor Circuit Low Input (signal shorted to ground), often from the same wiring fault.
• P0118 — Indicates ECT Sensor Circuit High Input (signal circuit is open), often from the same wiring fault.
• P0330 — Knock Sensor 2 Circuit Malfunction. TSB SSM 48991 notes that the ECT and knock sensor share a wiring harness, and a fault can trigger both codes.
• P1299 — Indicates Cylinder Head Overtemperature Protection is active. The PCM may trigger this as a fail-safe in response to an illogical ECT signal.

Technical Service Bulletins (TSBs) & Recalls

• SSM 48991: Mentions that various DTCs, including P0119, may be due to the engine coolant temperature (ECT) sensor or knock sensor wiring harness, and recommends replacing both in some cases.
• SSM 47791: States that P0119 on 2.7L engines may be due to an ECT sensor connector which is not fully seated or has damaged wiring between specific harness connectors (C1016 and C1168 for the MKX).
• SSM 46906: An earlier bulletin that also identifies a poorly seated ECT connector or damaged wiring as a likely cause for P0119 and related codes on the 2.7L engine.

Platform-Specific Known Issues

• TSB SSM 47791 and SSM 46906 note that on 2.7L engines, the P0119 code may be caused by an ECT sensor connector that is not fully seated or has damaged wiring, specifically between main harness connectors C1016 and C1168.
• TSB SSM 48991 expands on this, indicating the issue could be in the shared ECT sensor and knock sensor wiring harness, causing a group of potential DTCs including P0119 and P0330.

Mechanic-Grade Diagnostic Values

• ECT Sensor Resistance (Cold) — expected: 2,000 - 3,000 Ω at 68°F / 20°C. Failure: An open circuit (infinite resistance) or a value significantly outside this range indicates a faulty sensor.
• ECT Sensor Signal Voltage (Hot) — expected: Approximately 0.3V to 3.7V during normal operation. Failure: Voltage that is erratic, jumping between high and low values, or dropping out intermittently will trigger P0119.
• ECT Sensor Reference Voltage (Key On, Engine Off, Sensor Unplugged) — expected: 5 Volts on one pin of the connector harness. Failure: Absence of 5V reference points to a wiring issue or a problem with the PCM.
• ECT Sensor Ground Circuit (Key On, Engine Off, Sensor Unplugged) — expected: Good ground on the other pin of the connector harness. Failure: A lack of a solid ground points to a break in the ground wire returning to the PCM.

Scan Tool Commands That Help

• Ford IDS (Integrated Diagnostic System): Datalogger for ECT PID — To monitor the Engine Coolant Temperature (ECT) Parameter ID (PID) in real-time. This allows a technician to graph the sensor's voltage over time to visually identify the intermittent drops or spikes that trigger P0119. Wiggling the harness while watching the graph is a key diagnostic step.
• Ford IDS (Integrated Diagnostic System): KOEO (Key On, Engine Off) Self-Test — The KOEO self-test can sometimes flag circuit integrity faults that may not be present as a continuous DTC. A code 21, 51, or 61 on older OBD-I systems corresponds to ECT circuit faults and similar logic is used in the OBD-II self-test.
• High-end Aftermarket (e.g., FOXWELL NT710): Active Test / Bidirectional Control — While you cannot directly command the ECT sensor, you can use bidirectional controls to activate components that rely on its reading, such as the cooling fans. Forcing the fans on can help verify if the fan control module and fans are working, helping to isolate the fault to the sensor circuit.

Wiring & Ground Locations

• C1016 — This is a major harness connector for the engine. Its precise location can be found in the vehicle's workshop manual, but it is part of the path between the ECT sensor and the PCM.. TSB SSM 47791 specifically identifies the wiring between connectors C1016 and C1168 as a potential location for damage that causes P0119 on the Lincoln MKX.
• C1168 — This is the other major harness connector implicated in TSB SSM 47791. It is also part of the engine wiring harness.. Damage to the wiring between C1016 and C1168 is a known cause of intermittent ECT sensor signals, leading directly to code P0119.
• G104 / G105 — These are primary engine compartment ground points, typically located on the frame rail or engine block near the front of the engine bay.. The PCM and its sensor circuits rely on a solid ground connection. A corroded or loose main ground at G104 or G105 can introduce electrical noise and intermittent voltage drops across the entire system, potentially causing erratic sensor readings like those seen with P0119.

Real Owner Repair Stories

• Ford Edge Forum user (2016 Ford Edge with 2.7L EcoBoost (mechanically similar to MKX)) — Engine Coolant Over Temperature warning, fans running on high, codes P0117 and P0119.
  ❌ Tried (didn't work) Initial diagnosis pointed to a bad sensor, but the owner was hesitant due to the high labor cost of replacement.
  ✅ What actually fixed it The user found evidence of rodent damage on the wiring harness in the engine valley, near the sensor. Repairing the chewed wires resolved the codes and symptoms. This aligns with the TSBs pointing to wiring faults over sensor faults.