P0021 on 2015-2019 Ford Taurus: Causes and Fixes for Over-Advanced Cam Timing (Bank 2)

What's Unique About the 2015-2019 Ford TAURUS

The 3.5L V6 engines (both naturally aspirated and EcoBoost), part of Ford's 'Cyclone' engine family, utilize a Variable Camshaft Timing (VCT) system that is notoriously sensitive to oil condition and level. Ford has issued multiple Technical Service Bulletins (TSBs) highlighting that small debris or sludge in the oil can cause the VCT solenoids to stick, leading directly to codes like P0021. This makes regular, high-quality oil changes especially critical on this platform to prevent this common fault. The solenoids are located under the valve covers, making their replacement more labor-intensive 🎬 See this walkthrough on how to replace the intake VCT solenoid. than on some other engines where they are externally accessible.

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 is on
• Rough idle or stalling
• Hesitation or poor acceleration
• Decreased fuel economy
• Rattling or knocking noises from the engine
• Hard starting

Most Likely Causes

1. Low, Dirty, or Incorrect Viscosity Engine Oil 🔴 High Probability The VCT system uses oil pressure to adjust cam timing. Ford TSBs #SSM 47170 and #SSM 50067 directly state that debris in the oil can cause the VCT solenoid to stick, making oil quality a primary factor. This is the most common trigger for VCT-related codes on this engine.
   How to confirm: Check the engine oil dipstick for level and inspect the oil's condition. If it is dark, gritty, or below the 'add' line, this is the likely cause. An oil change is the first and most important diagnostic step.
   Typical fix: Perform an engine oil and filter change using the correct oil viscosity specified by Ford (typically SAE 5W-20 or 5W-30, check your owner's manual). Use a quality filter like the Motorcraft FL-500S. Clear the codes and drive to see if the issue is resolved.
   Est. part cost: $40-$80
2. Failing Variable Camshaft Timing (VCT) Solenoid 🔴 High Probability This is the component that physically controls oil flow to the cam phaser. As noted in Ford TSBs, it is prone to sticking due to contamination or simple electronic failure. TSB 16-0038 also calls for replacing the solenoid for this code when present with other codes.
   How to confirm: After verifying oil is good, swap the Bank 2 intake VCT solenoid with the Bank 1 intake solenoid. Bank 2 is on the radiator side, Bank 1 is on the firewall side. If the trouble code changes to P0011 (Bank 1), the solenoid is faulty. This is the most definitive DIY diagnostic step.
   Typical fix: Replace the Bank 2 intake VCT solenoid. On the 3.5L V6, the solenoids are located under the valve cover, which must be removed for access. Many technicians recommend replacing both the intake and exhaust solenoids on the same bank at the same time, or even all four solenoids, to prevent future failures.
   Est. part cost: $30-$90
3. Failing Camshaft Phaser 🟡 Medium Probability The phaser is the mechanical gear that the solenoid acts upon. It can fail by getting stuck in the advanced position, especially if the vehicle was driven for a long time with a faulty solenoid or oil issues. A rattling noise on startup is a common symptom of a failing phaser.
   How to confirm: This is diagnosed after confirming the oil and VCT solenoid are good. Advanced diagnostics using a scan tool to monitor commanded vs. actual cam angle, or physical inspection during a timing chain service, are required.
   Typical fix: Replace the Bank 2 intake camshaft phaser. This is a labor-intensive job that often involves replacing the timing chain, guides, and tensioners at the same time.
   Est. part cost: $100-$300 for the phaser, but a full timing kit can be $500+

Rare But Worth Checking

• Stretched Timing Chain: While not as common as on earlier engine models, a stretched timing chain can cause correlation issues and trigger this code, especially on very high-mileage vehicles or those with poor maintenance history. This often presents with rattling noises and may be accompanied by codes like P0018.
• Wiring or Connector Issue: Damage to the wiring harness or a poor connection at the VCT solenoid can interrupt the signal from the PCM, causing a fault. The connector is located on the valve cover.
• Faulty Powertrain Control Module (PCM): This is extremely rare. The PCM should only be considered as the cause after all other possibilities (oil, solenoid, phaser, wiring) have been exhaustively ruled out.

Diagnosis Steps

1. Check Engine Oil: Verify the oil level is correct and the oil is clean and of the proper viscosity (check owner's manual). If low or dirty, perform an oil and filter change, clear the code, and drive the vehicle to see if the code returns. This is the most critical first step.
2. Inspect VCT Solenoid Connector: Check the wiring and electrical connector for the Bank 2 (front/radiator side) intake VCT solenoid for any signs of damage, corrosion, or loose pins.
3. Swap VCT Solenoids: A common and effective diagnostic step is to swap the Bank 2 intake solenoid with the Bank 1 intake solenoid (located on the rear/firewall side valve cover). This requires removing both valve covers. Clear the codes and drive the vehicle. If the code changes to P0011, you have confirmed the solenoid is the faulty part.
4. Test the Solenoid (Optional): If you have a multimeter, you can test the resistance of the solenoid. It should typically be between 6.9 and 7.9 ohms. You can also carefully apply 12V to the solenoid to see if it actuates (clicks).
5. Advanced Diagnosis: If the oil is good and the solenoid tests fine (or the code did not move after swapping), the problem is likely more complex. This points towards a failing camshaft phaser or a timing chain issue. This level of diagnosis requires a professional scan tool to monitor VCT command vs. actual PIDs and likely significant engine disassembly.

Parts You'll Likely Need

• Variable Camshaft Timing (VCT) Solenoid (OEM #AT4Z-6M280-B) — This is the most common part to fail for code P0021. It gets stuck due to oil debris or internal failure, preventing correct camshaft timing adjustment. This part number is for the Bank 2 (radiator/driver side) intake solenoid.
  Trusted brands: Motorcraft, Dorman, Duralast, TRQ
  OEM price range: $50-$90
  Aftermarket price range: $30-$60
• Engine Oil and Filter (OEM #FL-500S (Filter)) — Low, dirty, or incorrect viscosity oil is a primary trigger for VCT system faults and code P0021. An oil change is the first recommended step.
  Trusted brands: Motorcraft, Mobil 1, Castrol
  OEM price range: $50-$80
  Aftermarket price range: $40-$60

Related Codes That Often Appear With This One

• P0011 — This is the equivalent code for Bank 1. If both appear, it strongly suggests a systemic problem like severely low/dirty oil or low oil pressure affecting the entire engine.
• P0018 — This code indicates a correlation issue between the crankshaft and the Bank 2 camshaft. It can appear alongside P0021 if the timing deviation is significant, potentially pointing towards a more serious timing chain or phaser issue.

Technical Service Bulletins (TSBs) & Recalls

• SSM 54366: General diagnostic procedure for multiple VCT codes, including P0021.
• SSM 47170: Notes that P0021 can be caused by small debris causing the VCT solenoid to stick.
• SSM 50067: Similar to SSM 47170, points to debris in oil as a cause for a sticking VCT solenoid.
• TSB 16-0038: Recommends replacing the affected VCT solenoid on some 2016 3.5L engines when certain codes appear together.

Platform-Specific Known Issues

• Ford Technical Service Bulletin #SSM 47170 notes that vehicles may exhibit P0021 due to 'small debris causing the VCT solenoid to stick.' It advises performing an oil and filter change before any component replacement.
• Ford Technical Service Bulletin #SSM 50067 reiterates the issue from TSB 47170, pointing to debris causing the VCT solenoid to stick.
• Ford Technical Service Bulletin #SSM 54366 lists P0021 among a wide range of VCT codes and refers technicians to specific diagnostic pinpoint tests in the workshop manual.
• Ford Technical Service Bulletin #TSB 16-0038 applies to some 2016 models with the 3.5L engine, directly instructing technicians to replace the Bank 2 intake VCT solenoid if P0018 and P0021 are found together.

Mechanic-Grade Diagnostic Values

• VCT Solenoid Internal Resistance — expected: 6.9 - 7.9 Ohms at 68°F (20°C). Failure: A reading of 0 ohms (short), infinite resistance (open circuit), or a value significantly outside the specified range.
• VCT Solenoid Connector Voltage — expected: Approximately 12V (Battery Voltage). Failure: Significantly lower or no voltage at the power supply pin indicates a wiring, fuse, or PCM power relay issue.
• Scan Tool PID: VCT_INT_DIF2 (ANGL) — expected: Close to 0 degrees at hot idle.. Failure: A large, persistent deviation from 0 degrees (e.g., more than +/- 5 degrees) at idle indicates the camshaft is not at its commanded (base) position, confirming a timing error.

Hidden / Shadow Codes Worth Checking

• N/A for VCT: For Ford VCT system faults like P0021, advanced diagnosis does not typically rely on hidden or Mode 6 codes. Instead, technicians use live data PIDs on a capable scan tool. (see via Monitor live data PIDs such as VCT_INT_ACT2 (actual angle) and VCT_INT_DIF2 (error angle) using a scan tool like Ford IDS or FORScan. The error PID is the most direct indicator of a problem.)

Scan Tool Commands That Help

• Ford IDS, FORScan, or equivalent professional scan tool: On-Demand Self-Test — Use this function after checking for basic issues like oil level. The test commands the PCM to check all electrical circuits, including the VCT solenoid's. If the test passes without setting a circuit code (e.g., P0020), it confirms the wiring and PCM driver are likely good, pointing towards a mechanical or hydraulic issue with the solenoid or phaser.
• Ford IDS, FORScan, or equivalent professional scan tool: Cycle VCT Solenoid (Output State Control) — As suggested by Ford TSB #SSM 50067, this command can be used to manually actuate the solenoid. A successful actuation that changes engine idle confirms the solenoid is electrically functional. It can sometimes dislodge small debris, temporarily fixing the issue and confirming contamination as the root cause.

Wiring & Ground Locations

• VCT Solenoid Connector — On the top of the Bank 2 (front/radiator side) valve cover. It is a 2-wire connector, often black.. This is the primary electrical connection for the solenoid. One pin receives ~12V power with the key on, and the other is a pulse-width modulated ground controlled by the PCM. Damage here or oil contamination can cause a loss of control.
• Main Engine Ground Strap — For the Taurus platform, the main engine-to-chassis ground is often located on the transmission case, below the brake booster area.. While not a direct cause, a poor main ground can create a host of unpredictable electrical issues and floating voltages for various sensors and actuators, including the VCT system. Ensuring this connection is clean and tight is a good practice during any electrical diagnosis.

OEM Part Supersession History

• Varies → AT4Z-6M280-A, AT4Z-6M280-B, AT4Z-6M280-C — Ford uses different VCT solenoids for intake vs. exhaust and for left vs. right banks on the 3.5L engine.
  Heads up: This is a common parts ordering trap. For P0021 ('A' Camshaft, Bank 2), the correct part is the Bank 2 INTAKE solenoid, which is OEM part number AT4Z-6M280-B. Part AT4Z-6M280-A is for Bank 1 Intake/Bank 2 Exhaust, and AT4Z-6M280-C is for Bank 1 Exhaust. The parts are physically different and not interchangeable.

Model Year Variations Within This Range

• 2015-2019: The standard 3.5L V6 (Duratec) and the 3.5L EcoBoost V6 offered in the Taurus remained consistent through its final model year in 2019. Unlike the F-150, the Taurus did not receive the 'Gen 2' 3.5L EcoBoost with dual port/direct injection. Therefore, the VCT system and associated diagnostics are the same across this entire year range for the specified engines.