P0021 on 2016 Ford Expedition 3.5L EcoBoost: Causes for Over-Advanced Cam Timing

What's Unique About the 2016-2016 Ford Expedition

The 3.5L EcoBoost engine's VCT system is highly sensitive to oil quality and maintenance, with many owners and technicians recommending 5,000-mile oil change intervals to prevent issues. Issues are common enough that Ford has issued multiple Technical Service Bulletins (TSBs). For the 2016 model year specifically, TSB 16-0038 (superseded by TSB 16-0093) addresses this code appearing on low-mileage vehicles, pointing directly to a faulty VCT solenoid as the cause when paired with P0018. A distinct rattling noise on a cold startup is a very common symptom on this platform that often, but not always, points to a more serious problem with the camshaft phasers or timing chain.

Symptoms You May Notice

• Illuminated Check Engine Light
• Rough idle
• Engine hesitation or stalling, especially during acceleration or when coming to a stop
• Reduced fuel economy
• Loud rattling or ticking noise from the engine for a few seconds on a cold start
• Noticeable loss of engine power, especially under load
• Vehicle may enter a reduced power "limp mode"

Most Likely Causes

1. Low, Dirty, or Incorrect Viscosity Engine Oil 🔴 High Probability The 3.5L EcoBoost's VCT system is hydraulic and extremely sensitive to oil pressure and cleanliness. Extended oil change intervals can lead to sludge and debris that clog small passages in the VCT solenoids.
   How to confirm: Check the oil level on the dipstick and inspect its color and consistency. Note the mileage since the last oil change; intervals over 5,000-7,500 miles are not recommended for this engine.
   Typical fix: Perform an engine oil and filter change using the manufacturer-specified SAE 5W-30 full synthetic or synthetic blend oil (meeting Ford spec WSS-M2C961-A1) and a quality filter like the Motorcraft FL-500S.
   Est. part cost: $40-$80
2. Faulty Bank 2 (Driver's Side) Intake VCT Solenoid 🔴 High Probability → Shop Engine Variable Valve Timing (VVT) Solenoid Ford has issued multiple service bulletins (SSM 50067, TSB 16-0038) indicating these solenoids can stick due to debris from engine oil or fail internally on the 3.5L engine. A small piece of an internal control ring can break off and jam the solenoid's spool valve, causing it to stick.
   How to confirm: Use a scan tool to command the solenoid on and off; a change in engine idle indicates it's working mechanically. A more definitive test is to swap the Bank 2 intake solenoid with the Bank 1 intake solenoid. Clear codes and drive. If the code changes to P0011, the solenoid is confirmed bad. You can also test the solenoid's internal resistance with a multimeter; a reading between 6.9-7.9 ohms is expected 🎬 Watch: A step-by-step guide to testing and fixing P0021. at room temperature.
   Typical fix: Replace the Bank 2 (driver's side) intake VCT solenoid and valve cover gasket. It is often recommended to replace all four VCT solenoids at the same time since the labor is intensive.
   Est. part cost: $30-$70
3. Worn Camshaft Phasers 🟡 Medium Probability → Shop Engine Camshaft The 3.5L EcoBoost is known for cam phaser issues, often causing a loud rattle on cold starts as the internal locking pin fails to engage. This prevents the phaser from holding its base timing position, leading to timing codes. Ford has released updated phaser designs to address this.
   How to confirm: A persistent 2-5 second rattle on cold startup is the primary indicator. Diagnosis requires a professional technician to analyze scan tool data (commanded vs. actual cam angle) and ultimately requires disassembling the front of the engine for inspection.
   Typical fix: This is an extensive repair that involves replacing all four camshaft phasers, along with the timing chain, tensioners, and guides. It is a 10+ hour job. 🎬 Watch: See what's involved in a full timing set replacement.
   Est. part cost: $400-$1200
4. Stretched Timing Chain or Failed Tensioner/Guides ⚪ Low Probability → Shop Engine Timing Chain Over time, especially with poor maintenance, the primary timing chain can stretch. The plastic tensioners and guides can also wear or break, causing a loss of tension and allowing the timing to jump.
   How to confirm: This is diagnosed by observing correlation codes (like P0018) alongside P0021, listening for chain slap noise, and ultimately, by physically inspecting the timing components, which is labor-intensive.
   Typical fix: Replace the timing chain, tensioners, and guides. This is often done at the same time as a cam phaser replacement.
   Est. part cost: $200-$500

Rare But Worth Checking

• Wiring Harness or Connector Issue: Damage to the wiring for the VCT solenoid or oil contamination in the electrical connector can mimic a failed solenoid. Always inspect the harness and connector when replacing the part.
• Clogged Oil Passages: In high-mileage engines or those with a poor maintenance history, sludge can build up and restrict oil flow in the passages leading to the VCT solenoids and phasers, causing pressure issues.

Diagnosis Steps

1. Check the engine oil level and condition. If low, dirty, or past its service interval, perform an oil and filter change with Ford-specified 5W-30 oil and a Motorcraft filter. Clear codes and test drive.
2. Scan for any other DTCs. Address any camshaft position sensor circuit codes (like P0345) first, as recommended in diagnostic aids.
3. Use a bidirectional scan tool to monitor the commanded vs. actual camshaft position PIDs for Bank 2. Also monitor the VCT error PID (VCT_ADV_ERR). A large and fluctuating variance (greater than +/- 5 degrees) points to a problem.
4. As recommended by Ford TSB SSM 50067, use the scan tool to cycle the Bank 2 intake VCT solenoid up to 10 times to attempt to dislodge any debris. If this temporarily resolves the issue, the solenoid is sticking.
5. Inspect the wiring harness and electrical connector for the Bank 2 intake VCT solenoid. Check for damage, loose connections, or oil contamination.
6. If the solenoid is suspected, swap the Bank 2 intake solenoid with the Bank 1 intake solenoid. Clear codes and drive the vehicle. If the code returns as P0011 (Bank 1), the solenoid is faulty and needs replacement.
7. If all previous steps fail to resolve the issue and a cold-start rattle is present, the cause is likely a mechanical failure in the timing system (cam phasers, timing chain). This requires professional diagnosis and repair.

Parts You'll Likely Need

• Intake Variable Camshaft Timing (VCT) Solenoid (Bank 2) (OEM #BL3Z-6M280-B) — This is the most common part to fail for this specific code on this engine, often due to sticking from oil debris. TSB 16-0038 specifically calls for its replacement if P0018 and P0021 are present on a low-mileage vehicle.
  Trusted brands: Motorcraft, Dorman
  OEM price range: $40-$60
  Aftermarket price range: $25-$50
• Camshaft Phaser & Timing Chain Kit (OEM #BL3Z-6D256-C) — If a cold-start rattle is present and the VCT solenoid is ruled out, worn cam phasers are the next likely cause. It is best practice to replace the phasers, timing chains, guides, and tensioners as a complete kit.
  Trusted brands: Motorcraft
  OEM price range: $600-$1200
  Aftermarket price range: $400-$800
• Valve Cover Gasket (Bank 2) (OEM #BL3Z-6584-A) — This gasket must be replaced when accessing the VCT solenoids, which are located under the valve cover.
  Trusted brands: Motorcraft, Fel-Pro
  OEM price range: $30-$50
  Aftermarket price range: $20-$40

Related Codes That Often Appear With This One

• P0018 — This is a Crankshaft/Camshaft Correlation code for the same bank (Bank 2). TSB 16-0038 specifically notes that P0018 and P0021 appearing together on a low-mileage 2016 3.5L engine points directly to a faulty Bank 2 intake VCT solenoid. In some cases, owners report these codes returning even after a full timing job, indicating a persistent solenoid or wiring issue.
• P0011 — This is the same over-advanced code but for Bank 1 (passenger side). If both codes are present, it strongly suggests a systemic issue like severe oil contamination or low oil pressure affecting the entire engine. It will also appear if you swap a bad Bank 2 solenoid to Bank 1 for diagnosis.
• P0022 — This is for an 'over-retarded' condition on the same bank. Seeing P0021 and P0022 together can indicate a very erratic VCT solenoid that is sticking in both directions or a severe mechanical timing problem.

Technical Service Bulletins (TSBs) & Recalls

• TSB 16-0038 / 16-0093 — For 2016 models with the 3.5L GTDI engine and under 2,000 miles, this TSB advises replacing the Bank 2 intake VCT solenoid if DTCs P0018 and P0021 are present together. TSB 16-0093 superseded 16-0038, expanding the vehicle list.
• SSM 50067 — A Special Service Message from Ford noting that VCT codes like P0021 can be caused by small debris in the oil causing the solenoid to stick. It recommends using a scan tool to cycle the solenoid 10 times to try and clear it before replacement.
• TSB 15-0131 — Addresses the common 'cold start rattle' on 3.5L EcoBoost engines by replacing the primary timing chain. While not a direct fix for P0021, it addresses a common root cause (stretched chain) that can lead to this code.

Mechanic-Grade Diagnostic Values

• VCT Solenoid Internal Resistance — expected: 6.9 to 7.9 Ohms at 68°F (20°C). Some general guides state a wider range of 5-15 Ohms.. Failure: A reading outside the specified range (open circuit or short) indicates a failed solenoid coil.
• VCT Solenoid Connector Voltage (Key On, Engine Off) — expected: Battery voltage (~12V) should be present at the power supply pin in the connector.. Failure: No voltage indicates a wiring issue, blown fuse, or problem with the PCM power relay.
• Scan Tool PID: VCT_ADV_ERR (VCT Error) — expected: Should be close to 0° at a stable, warm idle.. Failure: A consistent deviation of more than +/- 5 degrees, or large, erratic fluctuations (e.g., -45° to +26°), indicates the camshaft is not tracking the PCM's command, pointing to a sticking solenoid or mechanical issue.
• Engine Oil Pressure (at hot idle, via mechanical gauge) — expected: Minimum of 20-25 PSI.. Failure: Pressure below 15 PSI is a critical sign of excessive internal engine wear (e.g., bearings, tensioner seals) that can starve the VCT system and cause timing codes.

Hidden / Shadow Codes Worth Checking

• Mode $06, Test ID $53: This test monitor tracks the bank-to-bank timing error for the VCT system. A failed test result can be an early indicator of a developing VCT problem, sometimes before a full-blown DTC like P0021 is triggered. (see via A professional scan tool or advanced DIY software like FORScan that can access Mode $06 data.)

Scan Tool Commands That Help

• Ford IDS / FORScan: VCT Solenoid Actuator Test (Pinpoint Test HK) — As recommended in Ford TSBs (SSM 50067), this command rapidly cycles the suspect VCT solenoid 10 times. It's used after an oil change but before part replacement to attempt to dislodge small debris causing the solenoid to stick. If the code clears after running this test, it confirms a temporary blockage rather than a hard failure.

Wiring & Ground Locations

• VCT Solenoid Connector — On top of the VCT solenoid, located under the Bank 2 (driver's side) valve cover.. This is the primary connection point for testing the solenoid's resistance and for checking for power from the harness. Oil can leak into this connector, causing poor contact.
• G104 / G105 — G104 is located on the right (passenger) fender behind the battery. G105 is on the frame below the washer fluid container.. These are major chassis and engine bay ground points. While not exclusive to the VCT circuit, corrosion or a loose connection at these points can cause erratic voltage and signal issues for the PCM and various engine sensors, potentially contributing to false or intermittent timing codes.
• VCT Solenoid Pins — At the solenoid connector.. On similar Ford engines, Pin 1 is the 12V power supply from the PCM relay, and Pin 2 is the ground-side control wire that is pulsed by the PCM to actuate the solenoid. This is where voltage and resistance tests are performed.

Real Owner Repair Stories

• YouTube channel 'The Truck Lab' (2019 Ford F-150 3.5L EcoBoost) — Check Engine Light with codes P0018 and P0021, occasional loss of power, and a cold-start rattle.
  ❌ Tried (didn't work) The owner could have easily misdiagnosed the issue as failed cam phasers due to the cold-start rattle.
  ✅ What actually fixed it Diagnosis revealed a large variance in the VCT error PID for Bank 2. Replacing only the faulty Bank 2 VCT solenoid resolved all issues, including the P0021 code and the cold-start rattle, proving the solenoid can cause the rattle without phaser failure.
• Ford F150 Forum user 'acdcbean' (2019 Ford F-150 3.5L EcoBoost with 35k miles) — Check Engine Light with codes P0018 and P0021.
  ❌ Tried (didn't work) A complete replacement of all cam phasers by the dealer.
  ✅ What actually fixed it The codes returned immediately after the expensive phaser replacement. The user's story was unresolved in the thread, but it serves as a critical counter-example that throwing phasers at the problem does not always fix it, strongly suggesting the root cause was a faulty VCT solenoid, wiring, or PCM issue that was misdiagnosed.

When the Usual Fixes Don't Work

• In a documented case involving a 2019 F-150 with the 3.5L EcoBoost, a full cam phaser replacement was performed by a dealer to address P0018 and P0021, but the codes returned immediately upon driving the vehicle home. This indicates that even when the most common 'major' repair is performed, the root cause can still be a less expensive, overlooked component like a faulty VCT solenoid, a damaged wiring harness, or an intermittent connector issue that was not properly diagnosed before the teardown.

OEM Part Supersession History

• BL3Z-6M280-A → BL3Z-6M280-B — Internal design improvements for better durability and resistance to sticking from oil debris.
  Heads up: This part is for the Gen 1 (2011-2017) 3.5L EcoBoost. It is not interchangeable with the Gen 2 (2018+) engine's solenoid (e.g., HL3Z-6M280-A).
• BL3Z-6M280-B → AT4Z-6M280-A / AT4Z-6M280-B — Standard part revision and improvement by Ford for better robustness against debris and sticking.
  Heads up: Always verify the latest part number with a dealer using the vehicle's VIN, as multiple revisions exist.
• N/A → BL3Z-6D256-C (Kit P/N) — This is the comprehensive kit part number for the 2011-2016 F-150 and 2015-2017 Expedition/Navigator for a full timing job, including updated phasers to address cold start rattle issues.

Model Year Variations Within This Range

• 2016: The 2016 Expedition uses the first-generation 3.5L EcoBoost. This is important because its VCT solenoids (BL3Z-6M280-B) and cam phasers are different from the second-generation EcoBoost engine introduced in 2018+ models. While both generations have VCT issues, the specific part numbers are not interchangeable.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Timing Chain Stretch & Phaser Rattle 🔴 High → Shop Engine Timing Chain — Common, especially on vehicles over 70k miles or with extended oil change intervals. A cold-start rattle is the key symptom. (Ref: TSB 15-0131, TSB 20-2166)
• Carbon Buildup on Intake Valves 🟠 Medium — An inherent issue with all early direct-injection engines. Tends to cause rough idle and misfires at higher mileage (80k+ miles).
• Leaking Turbo Coolant Lines/Fittings 🟠 Medium — The fittings for the turbo coolant lines are known to leak coolant over time. It's a common issue but often a slow leak.
• Cracked or Leaking Valve Covers 🟡 Low → Shop Engine Valve Cover — The plastic valve covers can become brittle and crack or the gaskets can leak over time, causing oil leaks.
• Internal Water Pump Failure 🔴 High — While not specific to the EcoBoost, the base 3.5L engine family can have issues with the internal, timing-chain-driven water pump. Failure can be catastrophic, mixing coolant with engine oil.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this specific repair, using used parts is not recommended for any of the core timing components (solenoids, phasers, chains, tensioners). The only potentially acceptable used part would be a valve cover if the original was physically cracked or damaged, but even then, new gaskets are mandatory.

What to inspect on the donor part:

• Not applicable as used timing parts are not advised. These components wear and are highly sensitive to the previous engine's maintenance history and oil quality.

OEM-only on this vehicle (don't cheap out):

• Camshaft Phasers: Strongly recommend using only Motorcraft OEM parts. This is a critical, high-labor repair, and aftermarket phasers for this engine have a poor reputation for longevity.
• Timing Chains & Tensioners: Use only Motorcraft OEM parts to ensure proper fit and material strength. The cost savings of aftermarket kits do not justify the risk of premature stretching or failure.
• VCT Solenoids: While some aftermarket options exist, forum consensus strongly favors using Motorcraft solenoids. Aftermarket solenoids (including some from Dorman) have been reported to fail prematurely or be faulty out of the box, causing the codes to return.

Aftermarket brands forum-validated for this vehicle:

• Fel-Pro: A widely trusted brand for valve cover gaskets and seals if not buying the Motorcraft equivalent.

Brands owners have reported issues with on this vehicle:

• Dorman VCT Solenoids: Some owners have reported persistent issues and premature failures when using Dorman VCT solenoids on this platform, recommending sticking to OEM Motorcraft parts instead.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0011 — The Bank 1 equivalent of P0021; often appears if the faulty Bank 2 solenoid is swapped to Bank 1 during testing.
• P0018 — A crankshaft/camshaft correlation code for Bank 2 that frequently appears alongside P0021, especially in low-mileage TSB cases.
• P0022 — Indicates Bank 2 timing is over-retarded; often accompanies P0021 when the VCT solenoid is sticking or the phaser is failing.
• P0345 — Camshaft position sensor circuit code for Bank 2; diagnostic procedures recommend addressing this circuit code before troubleshooting P0021.
• P052D — Cold start intake camshaft timing over-retarded; frequently seen in conjunction with P0021 and cam phaser rattle issues.

Frequently Asked Questions