P0731 on 2011-2018 Lincoln Navigator: Gear 1 Incorrect Ratio Causes and Fixes

What's Unique About the 2011-2018 Lincoln NAVIGATOR

This year range covers two different Navigator generations with two different transmissions. The 2011-2017 models use the Ford 6R80 6-speed, which has a widely documented issue with its internal molded leadframe, also called a conductor plate. This part contains the speed sensors that trigger P0731 when they fail. This issue is also common on platform mates like the Ford F-150 and Expedition. The 2018 model uses the newer 10R80 10-speed, which has its own set of TSBs related to harsh shifting and internal valve body issues that can also cause this code.

Diagnostic Flowchart

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

Generation note: The 2011-2017 models belong to the third generation and use the 6R80 6-speed automatic transmission. The most common cause of P0731 on these models is a faulty molded leadframe. The 2018 model is the first year of the fourth generation and uses the 10R80 10-speed automatic. On this model, the code is more likely related to valve body or solenoid issues, as outlined in TSBs like 23-2123 and its successors.

Symptoms You May Notice

• Check Engine Light and/or Wrench Light illuminated.
• Harsh, delayed, or failed shifting into first gear.
• Vehicle gets stuck in a single gear (limp mode).
• Abrupt, unintended downshifts into first gear while driving.
• Speedometer drops to 0 or behaves erratically.
• Hesitation or lack of acceleration from a stop.
• Reduced fuel economy.

Most Likely Causes

1. Faulty Molded Leadframe / Conductor Plate (2011-2017 models) 🔴 High Probability The molded leadframe in the 6R80 transmission, which houses the input and output speed sensors, has a very high failure rate. Ford issued recalls and extended warranties (like 19N01) for this part due to the risk of sudden downshifts.
   How to confirm: A professional scan tool will show erratic or no signal from the transmission speed sensors. The presence of codes P0720 (Output Speed Sensor Circuit) or P0722 (Output Speed Sensor No Signal) alongside P0731 is a strong indicator of leadframe failure.
   Typical fix: Replace the molded leadframe, transmission filter, pan gasket, and fluid. It is also highly recommended to replace the valve body separator plate seals and the bulkhead sleeve connector at the same time.
   Est. part cost: $150-$400
2. Low or Dirty Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly The 10R80 transmission (2018+) is noted in TSBs as being sensitive to fluid condition and adaptive learning values. The 6R80 can also exhibit issues if the fluid is low or burnt.
   How to confirm: Check the transmission fluid level and condition. For the 6R80, the fluid should be red Mercon LV. For the 10R80, it should be red Mercon ULV. Burnt-smelling or dark fluid indicates a problem.
   Typical fix: Perform a complete fluid and filter change using the correct specification fluid. For 6R80, use Mercon LV. For 10R80, use Mercon ULV.
   Est. part cost: $100-$200
3. Main Control Valve Body Failure (2018+ models) 🟡 Medium Probability → Shop Transmission Valve Body TSB 23-2123 and newer bulletins like TSB 25-2023 indicate that 2018+ Navigators with the 10R80 can exhibit P0731 due to sticking valves or hydraulic leaks within the main control valve body.
   How to confirm: Diagnosis requires a technician to follow the specific steps in the TSB. If DTCs like P0731 are present, the procedure often skips software updates and goes directly to overhauling or replacing the valve body. 🎬 Watch: Common failure points on the 10R80 transmission
   Typical fix: Overhaul or replace the main control valve body assembly and perform an adaptive learning drive cycle.
   Est. part cost: $600-$1200
4. Incorrect Aftermarket Transmission Filter (6R80) ⚪ Low Probability → Shop Transmission Assembly
   How to confirm: This fault typically occurs immediately after a transmission service. An owner on a forum reported that an aftermarket filter was dimensionally incorrect, blocking fluid flow and causing P0731. The issue was resolved by installing an OEM Motorcraft filter.
   Typical fix: Replace the incorrect aftermarket filter with a genuine OEM Motorcraft transmission filter.
   Est. part cost: $40-$70

Rare But Worth Checking

• Internal Mechanical Failure: This includes worn clutch packs, a damaged planetary gear set, or a failing transmission pump. This is usually accompanied by significant metal debris in the transmission pan and is a much more expensive repair, often requiring a rebuild or replacement.
• Wiring Harness Damage: Damage to the wiring between the PCM/TCM and the transmission, particularly the main bulkhead connector, can cause communication errors, but this is less common than internal component failure.

Diagnosis Steps

1. Check for any open recalls or extended warranty programs (like 19N01) using the vehicle's VIN on the manufacturer's or NHTSA website.
2. Check the transmission fluid level and condition. Ensure it is full and does not appear burnt or contaminated. Verify the correct fluid type is in use (Mercon LV for 6R80, Mercon ULV for 10R80).
3. Use an OBD-II scanner to check for P0731 and any other related codes, such as P0720, P0722, or P1500, which strongly point to the leadframe on 6R80 models.
4. With a professional scan tool, monitor the live data for the transmission Input Speed Sensor (TSS) and Output Speed Sensor (OSS) while driving. Look for erratic signals or dropouts from the OSS when the fault occurs.
🎬 See how to test the output speed sensor signal
5. Inspect the transmission's main electrical bulkhead connector for corrosion or fluid intrusion.
6. For 2011-2017 models, if speed sensor codes are present or OSS data is erratic, the cause is almost certainly the internal molded leadframe. The next step is to drop the transmission pan for replacement.
7. For 2018 models, consult TSB 23-2123 or its successors. The procedure will guide diagnosis based on whether DTCs are present. With P0731 present, the TSB directs overhaul of the main control valve body.
8. If a transmission service was just performed, consider the possibility of an incorrect aftermarket filter restricting fluid flow.

Parts You'll Likely Need

• Transmission Molded Leadframe (Conductor Plate) (OEM #AL3Z-7G276-D) — This is the most common failure point on 2011-2017 Navigators with the 6R80 transmission, causing P0731. This part number supersedes AL3Z-7G276-A and AL3Z-7G276-B.
  Trusted brands: Motorcraft, Dorman
  OEM price range: $210-$320
  Aftermarket price range: $120-$200
• Automatic Transmission Fluid (OEM #XT-10-QLVC (Mercon LV), XT-12-QULV (Mercon ULV)) — Required for any service that involves dropping the transmission pan. The 6R80 (2011-2017) requires Mercon LV. The 10R80 (2018) requires Mercon ULV.
  Trusted brands: Motorcraft
  OEM price range: $80-$150
  Aftermarket price range: $60-$110
• Transmission Filter and Pan Gasket — Should always be replaced whenever the transmission pan is removed for service. Using an OEM filter is highly recommended to avoid fitment issues.
  Trusted brands: Motorcraft, Fel-Pro
  OEM price range: $40-$70
  Aftermarket price range: $25-$50

Related Codes That Often Appear With This One

• P0720 — Output Speed Sensor (OSS) Circuit Malfunction. The OSS is part of the molded leadframe assembly, making this code a primary indicator of leadframe failure.
• P0722 — Output Speed Sensor (OSS) No Signal. Also points directly to a failure of the leadframe.
• P1500 — Vehicle Speed Sensor Intermittent. This is another code directly linked to the leadframe failure in Ford's service bulletins and extended warranty programs.

Technical Service Bulletins (TSBs) & Recalls

• 19N01: Customer Satisfaction Program for transmission molded leadframe extended coverage, citing DTCs P0720, P0722, P0731, and/or P1500 as indicators for replacement.
• 16S19: Safety recall for unintended downshifts on 2012 models; remedy was a PCM software update.
• 23-2123: TSB for 2018-2021 models with the 10R80 transmission, addressing P0731 and other codes via a main control valve body overhaul.
• 25-2023: TSB for 2018-2021 models with the 10R80, also listing P0731 and pointing to internal hydraulic leaks related to the CDF clutch cylinder sleeve.

Platform-Specific Known Issues

• Customer Satisfaction Program 19N01: Ford/Lincoln extended the warranty on the molded leadframe for certain 2012-2013 Navigators to 10 years or 150,000 miles. This program specifically calls out DTCs P0720, P0722, P0731, and/or P1500 as conditions for a free replacement. This program has now expired for all eligible vehicles based on time.
• Safety Recall 16S19: This recall addressed unintended downshifts into first gear caused by the

Mechanic-Grade Diagnostic Values

• 6R80 Shift/Pressure Control Solenoid Resistance — expected: ~5.5 Ohms at 68°F (20°C). Failure: Significant deviation from 5.5 Ohms.
• 6R80 Shift Solenoid E (SSE) Resistance — expected: ~18 Ohms for units built after Nov 3, 2010. ~10.5 Ohms for units built before.. Failure: Reading does not match the vehicle's build date specification.
• 6R80 Solenoid Vacuum Test — expected: Holds over 21 in-Hg. Failure: Reading below 20 in-Hg indicates an internal leak in the solenoid.
• 6R80 Output Speed Sensor (OSS) Bench Test — expected: Using a 5V pull-up circuit, voltage should pulse between high and low as the output shaft is turned. Alternatively, a continuity tester will beep for each tooth that passes the sensor.. Failure: No pulse or beep when the shaft is turned.

Hidden / Shadow Codes Worth Checking

• Solenoid Body Strategy ID: A 13-digit calibration number unique to the valve body and its specific solenoid pack. This is not a DTC but is critical data stored in the PCM/TCM. An incorrect strategy ID can cause shifting issues. (see via Can be read using Ford's IDS, FORScan, or a high-level scan tool with Mode $09 (vehicle information) capabilities.)

Scan Tool Commands That Help

• Ford IDS: Clear TCM KAM (Keep Alive Memory) — This must be performed after replacing the leadframe or valve body to clear old adaptive values. The path is Toolbox > Powertrain > TCM > Reset KAM.
• FORScan: Transmission Characterization Update — Used to program the new Solenoid Body Strategy ID into the PCM/TCM after replacing a valve body. The path is Module Programming > Transmission Characterization Update.
• FORScan / High-Level Scan Tools: Clear Transmission Adaptive Tables — Used after any transmission repair or fluid change to force the TCM to relearn shift pressures and timing. This must be followed by the adaptive learning drive cycle.
• Any: Adaptive Learning Drive Cycle — After clearing adaptive tables, this specific driving procedure must be performed to allow the transmission to relearn shift points correctly. For the 10R80, it involves a series of light-throttle accelerations to 55 mph, gentle stops, and shifting through N and R, repeated multiple times.

Wiring & Ground Locations

• 6R80 Main Connector (C175T/C1616) — The main 16-pin round connector on the passenger side of the transmission case.. This is the primary interface between the vehicle harness and all internal transmission electronics, including the OSS on the leadframe. Technicians can perform resistance checks for all solenoids from these pins without dropping the pan. For example, SSE is pins 8 & 7, SSA is pins 9 & 7.

Real Owner Repair Stories

• Ford Truck Enthusiasts Forums (2015 Ford F-150 (Same 6R80 transmission)) — After a DIY transmission filter and fluid change, the truck would not move in any gear and threw a P0731 code.
  ❌ Tried (didn't work) Re-checking installation of the pan and fluid level., Searching for a replacement molded leadframe, assuming it had failed.
  ✅ What actually fixed it The aftermarket transmission filter from O'Reilly was dimensionally incorrect and slightly too long, causing it to contact the pan and block fluid flow. Replacing the aftermarket filter with a genuine OEM Motorcraft filter resolved the no-move condition and the P0731 code.
• YouTube Channel: 3D4KAUTO (2017 Ford F-150 5.0L with 6R80 transmission) — Vehicle stuck in 5th, 6th, and reverse gears only. Multiple transmission codes stored including P0706, P0707, and others related to the range sensor and solenoids.
  ❌ Tried (didn't work) Initial diagnosis pointed towards a full transmission replacement due to significant metallic debris (ferrous and non-ferrous) found in the pan, indicating mechanical wear.
  ✅ What actually fixed it Against advice, the customer requested to only replace the molded leadframe. The heavy accumulation of metal filings on the old leadframe's magnetic range sensor was likely causing the sensor to give false readings. After replacing only the leadframe and cleaning the pan, the transmission worked perfectly.

"I Checked Everything" — The Actual Cause

• A well-documented case occurred after a DIY transmission service where the fluid and filter were replaced. The truck immediately set a P0731 code and would not move. The fluid level was correct and the installation seemed fine. The actual cause was an incorrectly dimensioned aftermarket filter that was bottoming out against the pan, starving the transmission of fluid. Replacing it with an OEM filter fixed the problem instantly.

When the Usual Fixes Don't Work

• While the molded leadframe is the most common cause of P0731 on 6R80 transmissions, it is not the only one. In one documented case, a 2015 F-150 developed a P0731 and a no-move condition immediately after a transmission service. The owner suspected the leadframe had failed coincidentally. However, the actual cause was an aftermarket transmission filter that was dimensionally incorrect, blocking fluid pickup. Replacing the aftermarket filter with an OEM part completely resolved the issue, highlighting the importance of using quality parts even for simple maintenance.

OEM Part Supersession History

• AL3Z-7G276-A, AL3Z-7G276-B → AL3Z-7G276-D — The original leadframe designs were prone to failure of the integrated speed sensors and shorting of solenoid terminals from metallic debris.
  Heads up: The 'D' revision is the recommended replacement. It often includes a new foam strip to place over the solenoid contacts to prevent shorting, which was a common issue with the original design.

Model Year Variations Within This Range

• 2011-2017 (6R80): The resistance of Shift Solenoid E (SSE) changed. Units built before November 4, 2010 use a solenoid with ~10.5 Ohms resistance, while later models use one with ~18 Ohms. This is critical for accurate electrical diagnosis.
• 2015-2017 (6R80): Ford began installing two magnets in the transmission pan of 2015 and newer 6R80 transmissions, instead of one. This was to better capture metallic debris that was known to cause electrical shorts on the molded leadframe's solenoid contacts.