P2451 on 2021 Ford F-150: Causes of EVAP Switching Valve Code & Fixes

What's Unique About the 2021-2021 Ford F-150

While on most vehicles P2451 points to a failed valve or wiring, the 2021 Ford F-150 is a special case. Ford issued specific Technical Service Bulletins (TSBs) for this model year, acknowledging that software parameters within the powertrain control module (PCM) were incorrectly triggering this code, often alongside other seemingly unrelated codes like misfires. This means that instead of a mechanical repair, the most common and correct fix is a software update performed by the dealership. This is a known issue discussed by owners in online communities.

Diagnostic Flowchart

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

Symptoms You May Notice

• Illuminated Check Engine Light (MIL)
• Rough running engine, particularly at idle
🎬 See how to diagnose a rough idle on your F-150.
• Slight decrease in fuel economy
• A fuel odor may be noticeable

Most Likely Causes

1. Powertrain Control Module (PCM) Software Calibration Issue 🔴 High Probability → Shop Engine Control Module (ECM) Ford TSB 22-2151 and SSM 49573 specifically identify a software issue on 2021 F-150s with the 3.5L PowerBoost engine (built on or before April 23, 2021) that causes this code to be stored erroneously. This is the most widely reported cause in owner forums.
   How to confirm: A Ford dealer can check the vehicle's software version (calibration level) against the latest available calibration. If the software is outdated, TSB 22-2151 applies. The service is often covered under the 5-year/60,000-mile powertrain warranty.
   Typical fix: Reprogramming the PCM with the updated software calibration as per TSB 22-2151.
   Est. part cost: $0
2. Failed EVAP Switching Valve ⚪ Low Probability
   How to confirm: If the PCM software is up to date and the code returns, a technician can use a scan tool to command the valve to open and close. If it doesn't respond, and the wiring is intact, the valve has likely failed. The valve is located on or near the fuel tank and may require lowering the tank for access. 🎬 Watch: Locate the EVAP switching valve on the F-150.
   Typical fix: Replace the EVAP switching valve. This is considered a last resort after the TSB has been performed.
   Est. part cost: $30-$80
3. Wiring or Connector Issue ⚪ Low Probability
   How to confirm: Visually inspect the wiring harness and connector leading to the EVAP switching valve for damage, corrosion, or loose pins. A continuity test can be performed from the PCM to the valve connector. This is typically done only after the software update fails to resolve the code.
   Typical fix: Repair or replace the damaged section of the wiring harness or the connector.
   Est. part cost: $5-$50

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs). The first step for this specific vehicle and code is to check for TSBs 22-2151 and SSM 49573.
2. Verify PCM Software Version. Have a dealer or qualified shop check if the PCM software is the latest version. This is the most likely cause for vehicles built on or before April 23, 2021.
3. Update PCM Software. If an update is available, have the PCM reprogrammed. This will likely resolve the issue and is often covered by warranty.
4. Clear codes and perform a drive cycle. After the update, ensure the code does not return.
5. If the code persists, begin hardware diagnostics. Use a bidirectional scan tool to command the EVAP switching valve to operate. Listen for a click from the fuel tank area.
6. Inspect Wiring and Connectors. Check the harness and connector for the valve for any visible damage, corrosion, or loose connections.
7. Test the Valve. If wiring is good but the valve does not operate when commanded, it may have failed and require replacement. This is an unlikely scenario for this specific vehicle and code.

Parts You'll Likely Need

• Powertrain Control Module (PCM) Software Update (OEM #TSB 22-2151) — This is not a physical part, but the service is the most common fix required to address TSB 22-2151 and SSM 49573 for the 2021 F-150.
  Trusted brands: Ford
  OEM price range: $0-$200
  Aftermarket price range: N/A
• Evaporative Emission System Switching Valve (OEM #9U5Z-9F945-C) — This part should only be replaced if the PCM software update does not fix the code, and the valve is confirmed to be faulty through testing. The valve is sometimes called a vent control solenoid.
  Trusted brands: Motorcraft
  OEM price range: $50-$100
  Aftermarket price range: $30-$80

Related Codes That Often Appear With This One

• P0300, P0301-P0306, P0316 — These are misfire codes that are explicitly mentioned in TSB 22-2151 as appearing alongside P2451 due to the same PCM software issue.
• P050E — This code, related to cold start engine exhaust temperature, is also listed in TSB 22-2151 and SSM 49573.
• P0454 — An EVAP system pressure sensor intermittent code, also mentioned in TSB 22-2151.
• P1674 — A manufacturer-specific code also linked to the software issue in TSB 22-2151.

Technical Service Bulletins (TSBs) & Recalls

• TSB 22-2151
• SSM 49573

Platform-Specific Known Issues

• TSB 22-2151: Issued for some 2021 F-150s with the 3.5L PowerBoost engine built on or before April 23, 2021. It notes that P2451 (among other codes) can be caused by software parameters and directs technicians to reprogram the PCM.
• SSM 49573: This Special Service Message also applies to 2021 F-150s and mentions P2451 with symptoms of a rough running engine. It informed dealers that Ford was developing a calibration software update to fix the issue.
• Owner Experience: Owners on forums like F150Forum.com report getting the check engine light, taking it to the dealer, and having the issue resolved in a few hours with the TSB 22-2151 software flash, often under warranty. The consensus is to insist on the TSB before any hardware is replaced.
🎬 Watch: Owner explains the PowerBoost TSB and Ford's response.

Mechanic-Grade Diagnostic Values

• EVAP Switching Valve Commanded Voltage — expected: ~12 Volts (Battery Voltage) when commanded ON by a scan tool; ~0 Volts when commanded OFF.. Failure: If ~12V and ground are confirmed at the connector when commanded ON, but no audible click is heard from the valve, the valve has likely failed mechanically.
• Fuel Tank Pressure (FTP) Sensor Voltage (Static) — expected: 2.6V to 2.65V with Key On, Engine Off (KOEO).. Failure: A reading significantly different from this baseline before starting the engine can indicate a sensor or circuit issue, or a pre-existing pressure/vacuum condition in the tank.

Scan Tool Commands That Help

• Ford IDS (or equivalent professional scan tool): EVAP System Test / Manual EVAP Test — This is a guided diagnostic function within the Ford service tool to check the entire EVAP system's integrity. It can be used after a PCM update if the code returns, to verify hardware functionality.
• Ford IDS (or equivalent professional scan tool): Data Logger > Powertrain > Engine > EVAP Switching Valve Command — Use this bidirectional control to manually command the EVAP switching valve ON and OFF while physically listening for an audible click from the valve near the fuel tank to confirm mechanical operation.

Wiring & Ground Locations

• G101 — Located at the right front of the engine compartment.. A poor engine bay ground can affect various PCM-controlled solenoids and sensors. While not specific to the EVAP valve, it's a primary ground to check for general powertrain electrical issues.
• G200 — Located behind the instrument panel, near the center.. This is a key interior ground. Issues here could potentially affect the Body Control Module or other interior modules that communicate with the PCM regarding vehicle status.
• Rear Cabin Ground Stud — Behind the rear passenger seat trim panel, there is a factory ground stud on the body.. The EVAP switching valve is located near the fuel tank at the rear of the vehicle. While its harness may ground elsewhere, this is a major, accessible ground point in the vicinity that should be confirmed clean and tight if chasing a wiring issue.

Real Owner Repair Stories

• f150forum.com user report (2021 Ford F-150 Powerboost) — Check engine light with codes P0316, P0300, and P2451.
  ✅ What actually fixed it The dealer performed the software update outlined in TSB 22-2151, which updated the PCM and other modules. This cleared the P2451 and associated misfire codes. The issue did not reoccur.

OEM Part Supersession History

• 7U5Z-9F945-D, 7U5Z-9F945-E → 9U5Z-9F945-C — Part revision and update by manufacturer.

Model Year Variations Within This Range

• 2021 (Early Production): Vehicles built on or before April 23, 2021, are specifically called out in TSB 22-2151 as being prone to the software issue causing P2451. Vehicles built after this date likely have the updated PCM calibration from the factory.