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P0021 Code Explained: “A” Camshaft Position Timing Over-Advanced Bank 2 Causes, Symptoms & Fixes

OBD-II scanner displaying P0021 beside a Bank 2 intake camshaft phaser, VVT solenoid, advanced timing graphic and Check Engine Light

If your OBD-II scanner displays P0021, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected that the Bank 2 “A” camshaft is more advanced than commanded or remains advanced when it should return to its normal position.

On most dual-overhead-cam engines, Camshaft A refers to the intake camshaft, while Bank 2 is the side of the engine opposite Bank 1. Bank 1 contains cylinder number one, so Bank 2 is the other cylinder bank.

Modern engines use variable valve timing to adjust camshaft position according to engine speed, load, temperature and throttle input. When the ECM commands the Bank 2 intake camshaft to a specific angle but detects that it is too far advanced, it stores P0021.

P0021 is commonly caused by:

P0021 should not be ignored. Although some vehicles may continue running with only a Check Engine Light, an over-advanced camshaft can cause rough idle, poor acceleration, misfires, hard starting, increased emissions and potential engine damage.

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P0021 Quick Facts

ItemInformation
OBD-II codeP0021
Official description“A” Camshaft Position Timing Over-Advanced or System Performance Bank 2
CategoryPowertrain
SystemVariable valve timing
Code typeGeneric SAE powertrain code
SeverityModerate to high
Safe to drive?Limited driving only; diagnose promptly
Most common causesDirty oil, sticking VVT solenoid, failed phaser, timing-chain wear
Typical repair cost$60–$4,000+

What Does the P0021 Code Mean?

P0021 means “‘A’ Camshaft Position Timing Over-Advanced or System Performance Bank 2.”

The ECM commanded the Bank 2 intake camshaft to a certain position but detected that the camshaft:

The ECM determines camshaft position by comparing signals from the:

The ECM also monitors the command sent to the Bank 2 intake VVT solenoid.

When the actual camshaft angle does not match the commanded angle, P0021 may be stored.

P0021 is closely related to:

What Does Camshaft A Mean?

On most dual-overhead-cam engines:

The intake camshaft controls when the intake valves open and close.

Advancing intake camshaft timing can improve:

However, excessive intake-camshaft advance may cause:

Manufacturer terminology can vary, so confirm Camshaft A using vehicle-specific service information.

What Is Bank 2?

Bank 2 is the side of the engine that does not contain cylinder number one.

Bank 2 is used on engines with more than one cylinder bank, including:

Inline engines normally have only Bank 1.

Bank 2 may be located on either side of the vehicle depending on the engine design.

Confirm Bank 2 using:

Do not assume Bank 2 is always the driver or passenger side.

What Does Over-Advanced Camshaft Timing Mean?

Camshaft timing is considered advanced when the camshaft rotates ahead of its normal base position relative to the crankshaft.

The ECM intentionally advances and retards the camshaft under different operating conditions.

P0021 does not necessarily mean that all camshaft advance is abnormal. It means the Bank 2 intake camshaft is:

The fault may be hydraulic, mechanical or electrical.

How Variable Valve Timing Works

A typical variable valve timing system includes:

The system works as follows:

  1. The ECM calculates the desired camshaft angle.
  2. The ECM commands the VVT solenoid.
  3. The solenoid directs pressurized oil into the camshaft phaser.
  4. The phaser rotates the camshaft relative to the timing sprocket.
  5. The camshaft sensor reports the actual position.
  6. The ECM adjusts the solenoid command to maintain the desired angle.

If oil flow remains directed toward the advance chamber, the camshaft may stay over-advanced.

This may happen because of:

How the ECM Detects P0021

The ECM compares:

P0021 may be stored when:

Some vehicles require the condition to occur for several seconds before setting the code.

Others may detect the fault during startup, idle or deceleration.

Symptoms of the P0021 Code

Symptoms vary according to how far the camshaft is advanced and whether the fault is intermittent.

Common symptoms include:

Some vehicles may show no noticeable drivability symptoms beyond the warning light.

If the camshaft remains severely advanced, the engine may run poorly or fail to start.

Common Causes of P0021

1. Dirty Engine Oil

Dirty oil is one of the most common causes of variable valve timing problems.

Contaminated oil can create:

The VVT system relies on small oil passages and precise hydraulic control.

Even moderate contamination can interfere with operation.

2. Incorrect Oil Viscosity

Oil that is too thick or too thin may cause improper camshaft timing response.

Oil that is too thick may:

Oil that is too thin may:

Always use the manufacturer-specified oil viscosity.

3. Low Engine-Oil Level

Low engine oil can reduce pressure and cause inconsistent VVT operation.

Low oil may result from:

A low oil level may affect both banks, but the weakest or most restricted actuator may set a code first.

4. Low Engine-Oil Pressure

The oil level may be correct while actual oil pressure remains too low.

Possible causes include:

Low oil pressure can affect:

A mechanical oil-pressure test may be necessary.

5. Sticking Bank 2 Intake VVT Solenoid

The Bank 2 intake VVT solenoid controls oil flow to the camshaft phaser.

If the solenoid sticks in the advance position, the camshaft may remain over-advanced.

Possible causes include:

The solenoid may pass an electrical resistance test but still stick mechanically.

6. Clogged VVT Solenoid Screen

Some VVT solenoids have a small filter screen.

The screen may become clogged with:

A restricted screen can alter oil flow and prevent precise phaser control.

7. Restricted Oil Passages

Oil passages supplying or draining the phaser may become restricted.

Possible causes include:

A blocked return passage may keep oil trapped in the advance chamber.

8. Failed Bank 2 Intake Camshaft Phaser

The camshaft phaser may fail mechanically or hydraulically.

A failed phaser may:

A worn locking pin can allow the phaser to remain advanced when the engine is started.

9. Stretched Timing Chain

A stretched timing chain can alter camshaft position relative to the crankshaft.

Although chain stretch often causes retarded timing or correlation codes, some engine designs may interpret the resulting position as an over-advanced condition under certain operating conditions.

Common signs include:

10. Jumped Timing Chain or Belt

A timing chain or belt that jumps a tooth can place the Bank 2 intake camshaft outside its expected range.

Possible causes include:

A severely jumped timing system may cause:

11. Incorrect Mechanical Timing

P0021 may appear immediately after:

Possible mistakes include:

If P0021 appears after engine work, verify mechanical timing before replacing additional parts.

12. Faulty Camshaft Position Sensor

The Bank 2 intake camshaft position sensor may provide inaccurate or intermittent data.

Possible sensor faults include:

However, the sensor may be correctly reporting a real timing problem.

Do not replace it based only on P0021.

13. Shifted Camshaft Reluctor Wheel

The camshaft sensor reads a reluctor or trigger wheel attached to the camshaft or phaser.

The reluctor may become:

A shifted reluctor changes the signal received by the ECM, even if the valve timing is mechanically correct.

14. Damaged Wiring or Connectors

Wiring faults may prevent the ECM from controlling the VVT solenoid correctly.

Inspect for:

Electrical circuit problems may also store P0020.

15. Faulty ECM or PCM

ECM failure is uncommon but possible.

A damaged internal driver may:

Before replacing the ECM, verify:

16. Incorrect Replacement Components

Incorrect replacement parts may cause P0021.

Examples include:

A part may physically fit while having different hydraulic or timing characteristics.

Is P0021 an Electrical or Mechanical Code?

P0021 is primarily a camshaft timing performance code.

It does not directly identify a single failed electrical circuit.

The cause may be:

This differs from P0020, which primarily identifies an electrical fault in the Bank 2 intake camshaft actuator circuit.

P0021 indicates that the camshaft’s actual position does not match the ECM’s requested position.

How Serious Is the P0021 Code?

P0021 ranges from moderately serious to severe.

The seriousness depends on the cause.

A sticking VVT solenoid may cause poor performance but little immediate mechanical risk.

A jumped timing chain can cause severe engine damage.

Ignoring P0021 may lead to:

The code becomes especially serious when accompanied by:

Can You Drive With P0021?

Limited driving may be possible if:

Continued driving is not recommended until the cause is known.

Stop driving immediately if you notice:

A mechanical timing problem can become catastrophic without additional warning.

How to Diagnose P0021

Step 1: Scan for Additional Codes

Use an OBD-II scanner to check for related codes.

Common companion codes include:

Record:

Do not clear the codes before recording this information.

Step 2: Confirm Bank 2 and Camshaft A

Use vehicle-specific service information to identify:

Incorrect bank identification can lead to replacing the wrong components.

Step 3: Check the Engine-Oil Level

Check the oil with the vehicle positioned according to manufacturer instructions.

Look for:

Correct the oil level before continuing.

An overfilled engine may also create aerated oil and unstable VVT operation.

Step 4: Inspect Oil Condition and Viscosity

Determine whether the oil is:

Perform an oil and filter change if necessary.

Use the exact manufacturer-specified viscosity and oil standard.

Step 5: Review Maintenance and Repair History

Ask or determine:

P0021 appearing immediately after repair often indicates an installation problem.

Step 6: Inspect Wiring and Connectors

Inspect the Bank 2 intake VVT solenoid and camshaft-sensor circuits.

Look for:

Repair electrical faults before condemning mechanical components.

Step 7: Test the Bank 2 Intake VVT Solenoid Electrically

Test the solenoid for:

Compare all readings with manufacturer specifications.

A circuit fault may store P0020 in addition to P0021.

Step 8: Command the VVT Solenoid With a Scan Tool

Use a bidirectional scan tool when available.

Command the Bank 2 intake camshaft through its operating range.

Monitor:

Possible results include:

Step 9: Remove and Inspect the VVT Solenoid

Remove the Bank 2 intake VVT solenoid according to the service procedure.

Inspect for:

Clean or replace the solenoid as appropriate.

Do not use aggressive cleaning methods that may damage seals or internal coatings.

Step 10: Compare Bank 1 and Bank 2 Solenoids

If the intake VVT solenoids are identical, compare:

Some technicians temporarily swap identical solenoids between banks.

Only do this when:

If the fault moves to Bank 1, the solenoid is likely defective.

Step 11: Monitor Camshaft Position Data

Compare:

If Bank 1 responds normally while Bank 2 remains advanced, suspect a Bank 2-specific problem.

Possible causes include:

Step 12: Check Engine-Oil Pressure

Install a mechanical oil-pressure gauge if pressure problems are suspected.

Measure pressure at:

Compare results with factory specifications.

Do not assume oil pressure is normal because the dashboard warning light is off.

Step 13: Test the Camshaft Position Sensor

Inspect and test the Bank 2 intake camshaft position sensor.

Depending on sensor type, test:

Use an oscilloscope when possible.

A distorted signal can make a correctly positioned camshaft appear over-advanced.

Step 14: Compare Camshaft and Crankshaft Waveforms

Use an oscilloscope to compare:

Compare the waveform with known-good data.

This may reveal:

Step 15: Inspect the Camshaft Phaser

If the solenoid, wiring and oil pressure are correct, inspect the camshaft phaser.

Possible signs of phaser failure include:

Phaser replacement may require substantial engine disassembly.

Step 16: Verify Mechanical Timing

If scan data or waveform testing suggests a mechanical problem, verify timing alignment.

This may require removing:

Position the engine at top dead center and inspect:

Use required locking tools and manufacturer procedures.

Step 17: Inspect the Reluctor Wheel

If mechanical timing is correct but the code remains, inspect the camshaft reluctor.

Look for:

A shifted reluctor may require replacement of the camshaft or phaser.

Step 18: Check Technical Service Bulletins

Some vehicles have known P0021-related issues involving:

Review manufacturer information before performing major repairs.

Step 19: Verify the Repair

After completing repairs:

  1. Clear stored codes.
  2. Start the engine from cold.
  3. Listen for timing-system noise.
  4. Monitor commanded and actual camshaft position.
  5. Command the VVT system with a scan tool.
  6. Check for oil leaks.
  7. Complete the manufacturer’s drive cycle.
  8. Rescan for pending codes.

A successful repair should restore proper Bank 2 intake camshaft control and prevent P0021 from returning.

Common P0021 Repairs and Costs

RepairEstimated cost
Diagnostic inspection$100–$300
Engine oil and filter change$60–$180
Clean VVT solenoid or screen$100–$250
Repair VVT wiring$100–$600
Replace Bank 2 intake VVT solenoid$150–$500
Replace camshaft position sensor$150–$450
Clean restricted oil passages$200–$800
Replace Bank 2 intake camshaft phaser$600–$1,800
Replace timing-belt kit$700–$2,000
Replace timing chain, guides and tensioners$1,200–$4,000
Repair cylinder-head damage$2,500–$6,000+
Replace engine$4,000–$12,000+
ECM software update$100–$300
Replace and program ECM$1,000–$2,500+

Repair costs vary according to:

Common Diagnostic Mistakes

Replacing the Camshaft Position Sensor First

P0021 does not automatically mean the camshaft position sensor has failed.

The sensor may be correctly reporting that the camshaft is over-advanced.

Confusing P0021 With P0020

P0020 is an actuator electrical-circuit code.

P0021 indicates that actual camshaft timing is over-advanced or outside the expected range.

Confusing P0021 With P0022

P0021 means over-advanced timing.

P0022 means over-retarded timing.

Replacing the VVT Solenoid Without Checking the Oil

Dirty, low or incorrect oil can cause the same symptoms as a failed solenoid.

Always inspect the oil first.

Assuming an Oil Change Will Fix Mechanical Wear

Fresh oil may help a sticking solenoid.

It cannot repair:

Confusing Bank 1 and Bank 2

Bank 1 contains cylinder number one.

Bank 2 is the opposite bank.

Testing the wrong bank can lead to unnecessary parts replacement.

Confusing Camshaft A and Camshaft B

Camshaft A usually refers to the intake camshaft.

Camshaft B usually refers to the exhaust camshaft.

Confirm the designation before repairs.

Ignoring Startup Rattle

Startup rattling may indicate:

Ignoring the noise may lead to major engine damage.

Skipping Oil-Pressure Testing

A correct oil level does not guarantee correct pressure.

Low oil pressure can prevent proper phaser control.

Failing to Compare Both Banks

Comparing Bank 1 and Bank 2 operation can quickly show whether the fault is localized or system-wide.

Replacing the ECM Too Early

ECM failure is uncommon compared with:

Verify the entire system first.

Vehicles Commonly Affected by P0021

P0021 can appear on OBD-II vehicles equipped with multiple cylinder banks and intake variable valve timing.

Potentially affected manufacturers include:

P0021 is commonly associated with engines using:

The code alone does not prove that a particular model has a known defect.

Diagnosis must be based on the exact:

How to Prevent P0021

Helpful preventive measures include:

Good oil maintenance is one of the best ways to prevent camshaft-timing and VVT problems.

Frequently Asked Questions About P0021

What does code P0021 mean?

P0021 means the Bank 2 intake camshaft is more advanced than commanded or is not returning to its expected position.

Is Camshaft A the intake camshaft?

On most engines, yes.

Camshaft A usually refers to the intake camshaft.

Which side is Bank 2?

Bank 2 is the side of the engine that does not contain cylinder number one.

Its location varies by engine.

Is P0021 an electrical code?

Not primarily.

P0021 is a camshaft timing-performance code. The cause may still be electrical, hydraulic or mechanical.

What is the difference between P0020 and P0021?

P0020 identifies an electrical fault in the Bank 2 intake camshaft actuator circuit.

P0021 means the Bank 2 intake camshaft is over-advanced or not responding correctly.

What is the difference between P0021 and P0022?

P0021 indicates over-advanced camshaft timing.

P0022 indicates over-retarded camshaft timing.

Can dirty oil cause P0021?

Yes. Dirty oil can clog the VVT solenoid, phaser or oil passages.

Can low oil cause P0021?

Yes. Low oil can reduce hydraulic control of the VVT system.

Can the wrong oil viscosity cause P0021?

Yes. Incorrect viscosity can slow or destabilize camshaft-phaser operation.

Can a bad VVT solenoid cause P0021?

Yes. A sticking Bank 2 intake VVT solenoid is a common cause.

Can a bad camshaft phaser cause P0021?

Yes. A failed phaser may remain stuck in an advanced position.

Can a stretched timing chain cause P0021?

Yes. Timing-chain wear can alter camshaft position and trigger performance or correlation codes.

Can a bad camshaft sensor cause P0021?

Yes, but it is less common than oil, VVT solenoid, phaser or mechanical timing problems.

Test the sensor before replacement.

Can P0021 cause rough idle?

Yes. Excessive intake camshaft advance can cause rough idle and misfires.

Can P0021 cause hard starting?

Yes. Incorrect valve timing may cause extended cranking or hard starting.

Can P0021 cause a no-start condition?

Yes, especially if the timing chain or belt has jumped significantly.

Can I drive with P0021?

Limited driving may be possible if the engine runs normally and makes no unusual noise.

Prompt diagnosis is recommended because the code may indicate a serious timing-system problem.

Will an oil change fix P0021?

It may help if dirty or incorrect oil is causing a sticking VVT solenoid.

It will not repair a failed phaser, stretched chain, jumped belt or incorrect mechanical timing.

How much does it cost to fix P0021?

A basic oil service may cost under $200.

A VVT solenoid replacement commonly costs $150 to $500.

Timing-chain or camshaft-phaser repairs may cost $600 to $4,000 or more.

Will clearing P0021 fix the vehicle?

No. Clearing the code only removes the warning temporarily.

The code will return if the camshaft timing problem remains.

Will P0021 fail an emissions test?

Yes. An active Check Engine Light or emissions-related powertrain code will generally cause an OBD-based inspection failure.

Final Thoughts

The P0021 code means the Bank 2 intake camshaft is over-advanced or is not following the ECM’s commanded position.

The most common causes include:

Begin diagnosis by checking the oil level, condition and viscosity. Confirm Bank 2 and Camshaft A before inspecting the VVT solenoid and wiring.

Use a capable scan tool to compare commanded and actual camshaft position. If the camshaft remains advanced, inspect the solenoid, oil passages, oil pressure, camshaft phaser and mechanical timing.

Do not assume that P0021 is simply a bad sensor. The code may indicate a mechanical timing fault capable of causing severe engine damage.

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