P0109 on 2018-2019 Lincoln MKT: Intermittent MAP Sensor Causes and Fixes

What's Unique About the 2018-2019 Lincoln MKT

For the 2018-2019 Lincoln MKT with the 3.5L EcoBoost engine, this code is specifically addressed by a manufacturer TSB. Unlike a generic P0109 that could stem from various wiring or vacuum issues, on this specific platform, Ford has identified a high failure rate of the Manifold Absolute Pressure and Temperature (MAPT) sensor itself. This makes diagnosis more straightforward, as the sensor is the primary suspect by a wide margin. The TSB also covers the 2018-2019 Ford Explorer, Flex, and Taurus with the same engine, indicating a platform-wide component issue.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on
• Powertrain Malfunction (Wrench) light may be illuminated
• "Service AdvanceTrac" message on the 🎬 See how this common error code is diagnosed and fixed. dash
• "Hill Start Assist Not Available" message
• Lack of power or sluggish acceleration, may feel like a transmission issue
• Hesitation or stumbling when accelerating from a stop
• Rough or erratic idling
• Poor fuel economy

Most Likely Causes

1. Faulty Manifold Absolute Pressure and Temperature (MAPT) Sensor 🔴 High Probability This is a known failure part for this specific vehicle and engine combination, as documented by Lincoln in TSB 19-2212. The bulletin explicitly states this sensor is the likely cause for DTCs P0107, P0108, and/or P0109.
   How to confirm: Follow the diagnostic procedure in the original TSB (19-2183), which involves comparing the MAP sensor's pressure reading (MAP PRESS PID) to other pressure sensors at key-on, engine-off. If the reading deviates by more than 10.35 kPa (1.5 psi), the sensor is faulty. A visual inspection of the sensor for oil contamination or damage is also recommended. A technician in a YouTube video demonstrates the simple replacement, confirming it's the go-to fix.
   Typical fix: Replace the MAPT sensor. This is a straightforward repair that involves removing the engine cover, disconnecting a connector, and removing a single T20 Torx screw.
   Est. part cost: $35-$161
2. Damaged Wiring or Loose Connector ⚪ Low Probability While less common than sensor failure on this platform, wiring issues are always a possibility for intermittent circuit codes.
   How to confirm: Visually inspect the wiring harness and connector going to the MAPT sensor for any signs of corrosion, damage, or loose pins. Use a multimeter to check for a stable 5-volt reference, good ground, and a consistent signal wire voltage. The connector should be inspected for damage when unplugged.
   Typical fix: Repair the damaged section of the wiring harness or clean/replace the connector.
   Est. part cost: $5-$50

Rare But Worth Checking

• Major Vacuum Leak: A significant and intermittent vacuum leak near the sensor could potentially cause erratic readings, though this would likely trigger other codes as well.
• Powertrain Control Module (PCM) Issue: In very rare cases, the fault could be internal to the PCM, such as a failing analog-to-digital converter. This should only be considered after the sensor and wiring have been definitively ruled out.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and confirm P0109 is present, noting any other codes like P0107 or P0108.
2. Consult TSB 19-2212, which specifically addresses this issue for your vehicle and its platform mates.
3. Locate the MAPT sensor on the intake manifold. On the 3.5L EcoBoost, it is easily accessible on top of the engine after popping off the plastic engine cover.
4. Visually inspect the sensor's connector and wiring for any obvious damage, corrosion, or loose connections.
5. If the wiring looks good, the most likely cause is the sensor itself, per the TSB.
6. To replace, disconnect the electrical connector. Remove the single T20 Torx screw holding the sensor in place.
7. Gently twist and pull the old sensor out. It may require some wiggling to break the o-ring seal.
8. Wipe the mounting surface clean. Lightly lubricate the o-ring on the new sensor and press it firmly into place. Reinstall the screw and reconnect the electrical connector.
9. After replacement, clear the trouble codes with the scanner and perform a test drive to ensure the issue is resolved.

Parts You'll Likely Need

• Manifold Absolute Pressure and Temperature (MAPT) Sensor (OEM #AA5Z-9F479-E) — This is the component identified as faulty in the manufacturer's Technical Service Bulletin (TSB 19-2212) for this specific code and vehicle. It is also referred to by the Motorcraft part number CX2619.
  Trusted brands: Motorcraft, Bosch, Delphi, Standard Motor Products
  OEM price range: $78-$161
  Aftermarket price range: $34-$70

Related Codes That Often Appear With This One

• P0107 — This code for 'MAP Circuit Low Input' often appears with P0109 because a failing sensor can intermittently send a signal that is too low. Both are mentioned in TSB 19-2212.
• P0108 — This code for 'MAP Circuit High Input' can also accompany P0109 as the intermittent fault may cause voltage spikes. It is also listed in TSB 19-2212.

Technical Service Bulletins (TSBs) & Recalls

• TSB-19-2212: Supersedes TSB 19-2183. Addresses DTCs P0107, P0108, and/or P0109 on 2018-2019 MKT, Explorer, Flex, and Taurus with 3.5L EcoBoost engine, identifying a faulty MAPT sensor (part AA5Z-9F479-E) as the cause.
• TSB-19-2183: The original bulletin, which included a diagnostic step to compare PID values before replacing the sensor.

Platform-Specific Known Issues

• A Technical Service Bulletin (TSB 19-2212, superseding 19-2183) was issued by Ford/Lincoln for 2018-2019 MKT models with the 3.5L EcoBoost engine. It states that DTCs P0107, P0108, and/or P0109, along with symptoms like lack of power and various warning messages, are likely due to a faulty MAPT sensor.
• The TSB specifies a labor time of 0.3 hours for the repair on an MKT.

Mechanic-Grade Diagnostic Values

• MAP Sensor Pressure Deviation (KOEO) — expected: The MAP (PRESS) PID value should be within 10.35 kPa (1.5 psi) of the BARO (PRESS), TCBP (PRESS), and TURBO INLET (PRESS) PIDs.. Failure: A deviation greater than 10.35 kPa (1.5 psi) indicates a faulty MAPT sensor.
• MAP Sensor 5V Reference Wire Voltage (KOEO) — expected: 4.8V to 5.2V, steady.. Failure: Voltage outside this range indicates a wiring or PCM issue.
• MAP Sensor Signal Wire Voltage (KOEO) — expected: Approximately 2.0V to 3.0V for turbo applications at atmospheric pressure.. Failure: A signal voltage that is erratic, stuck, or significantly outside this range points to a sensor or wiring fault.
• MAP Sensor Ground Wire Voltage — expected: Under 0.05V (50mV).. Failure: A reading higher than 0.05V indicates a poor ground connection, which can cause incorrect sensor readings.

Scan Tool Commands That Help

• Ford IDS (or equivalent professional scanner): Live Data / PID Monitoring — Use with Key On, Engine Off to compare pressure sensor PIDs (MAP, BARO, TCBP, TURBO INLET) as the primary diagnostic step outlined in TSB 19-2183.

Wiring & Ground Locations

• Engine Wiring Harness — The MAPT sensor harness routes from the top of the intake manifold into the main engine loom.. While the sensor is the primary failure point, it's worth inspecting the visible portion of the harness for chafing or damage. Ford vehicles from this era have documented issues with harnesses rubbing against components like A/C lines or transmission casings, which can cause intermittent electrical faults.

OEM Part Supersession History

• 2R3Z-9F479-AA → AA5Z-9F479-A — Part revision and improvement.
• AA5Z-9F479-A (also sold as CX-2228) → AA5Z-9F479-E (also sold as CX-2619) — Updated design to address the failure mode described in TSB 19-2212.
  Heads up: Using the older part numbers may lead to a repeat failure.

Model Year Variations Within This Range

• 2018-2019: No significant variations are noted within the 2018-2019 model years for this specific issue. The TSB applies equally to both years, suggesting the same faulty part was used across this production run.