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:
- Dirty or incorrect engine oil
- Low engine-oil level
- Low or unstable oil pressure
- A sticking Bank 2 intake VVT solenoid
- A failed camshaft phaser
- Restricted VVT oil passages
- A stretched or jumped timing chain
- Incorrect mechanical timing
- A faulty camshaft position sensor
- A shifted reluctor wheel
- Damaged wiring or connectors
- An ECM software or control problem
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.
Looking for more diagnostic resources? Browse our complete OBD-II libraries:
- Complete OBD-II Code Library: https://my.prostreetonline.com/dtc-obdii/
- Body (B) Codes: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- Chassis (C) Codes: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
P0021 Quick Facts
| Item | Information |
|---|---|
| OBD-II code | P0021 |
| Official description | “A” Camshaft Position Timing Over-Advanced or System Performance Bank 2 |
| Category | Powertrain |
| System | Variable valve timing |
| Code type | Generic SAE powertrain code |
| Severity | Moderate to high |
| Safe to drive? | Limited driving only; diagnose promptly |
| Most common causes | Dirty 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:
- Advanced farther than expected
- Remained advanced too long
- Failed to return to its base position
- Moved differently than commanded
- Operated outside the acceptable timing range
The ECM determines camshaft position by comparing signals from the:
- Crankshaft position sensor
- Bank 2 intake camshaft position sensor
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:
- P0011: “A” Camshaft Position Timing Over-Advanced Bank 1
- P0018: Crankshaft Position–Camshaft Position Correlation Bank 2 Sensor A
- P0020: “A” Camshaft Position Actuator Circuit Bank 2
- P0022: “A” Camshaft Position Timing Over-Retarded Bank 2
- P0024: “B” Camshaft Position Timing Over-Advanced Bank 2
- P0009: Engine Position System Performance Bank 2
What Does Camshaft A Mean?
On most dual-overhead-cam engines:
- Camshaft A is the intake camshaft.
- Camshaft B is the exhaust camshaft.
The intake camshaft controls when the intake valves open and close.
Advancing intake camshaft timing can improve:
- Low-speed torque
- Cylinder filling
- Throttle response
- Combustion efficiency
However, excessive intake-camshaft advance may cause:
- Rough idle
- Poor high-RPM performance
- Increased emissions
- Misfires
- Hard starting
- Reduced engine vacuum
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:
- V6 engines
- V8 engines
- V10 engines
- V12 engines
- Horizontally opposed engines
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:
- Manufacturer service information
- A cylinder-numbering diagram
- A firing-order diagram
- Underhood labels
- A professional repair database
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:
- More advanced than commanded
- Advanced when no advance was requested
- Slow to return from an advanced position
- Unable to maintain the requested angle
- Outside the manufacturer’s acceptable timing range
The fault may be hydraulic, mechanical or electrical.
How Variable Valve Timing Works
A typical variable valve timing system includes:
- ECM or PCM
- VVT solenoid
- Camshaft phaser
- Engine-oil pressure
- Camshaft position sensor
- Crankshaft position sensor
- Internal oil passages
The system works as follows:
- The ECM calculates the desired camshaft angle.
- The ECM commands the VVT solenoid.
- The solenoid directs pressurized oil into the camshaft phaser.
- The phaser rotates the camshaft relative to the timing sprocket.
- The camshaft sensor reports the actual position.
- 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:
- A sticking solenoid
- A blocked return passage
- A failed phaser
- Incorrect oil pressure
- Mechanical timing error
How the ECM Detects P0021
The ECM compares:
- Commanded Bank 2 intake camshaft angle
- Actual Bank 2 intake camshaft angle
- Crankshaft position
- VVT solenoid duty cycle
- Camshaft response time
P0021 may be stored when:
- Actual camshaft advance exceeds the commanded value.
- The camshaft remains advanced after the ECM commands retard.
- The camshaft moves too slowly.
- Camshaft position remains outside a programmed limit.
- The phaser does not return to its base position.
- The camshaft signal indicates incorrect timing.
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:
- Illuminated Check Engine Light
- Rough idle
- Engine misfires
- Poor acceleration
- Reduced high-RPM power
- Engine hesitation
- Hard starting
- Extended cranking
- Engine stalling
- Poor fuel economy
- Increased emissions
- Strong exhaust odor
- Timing-chain rattle
- Metallic startup noise
- Limp mode
- Failed emissions inspection
- Reduced engine vacuum
- Backfiring through the intake
- Uneven engine operation
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:
- Sludge
- Varnish
- Carbon deposits
- Restricted oil passages
- Sticking VVT solenoids
- Slow camshaft-phaser movement
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:
- Flow slowly during cold starts
- Delay phaser movement
- Prevent the camshaft from returning quickly
Oil that is too thin may:
- Leak through worn phaser passages
- Reduce hydraulic control
- Create unstable camshaft movement
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:
- External oil leaks
- Excessive oil consumption
- Improper service
- Long oil-change intervals
- Internal engine wear
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:
- Worn oil pump
- Restricted oil pickup
- Excessive bearing clearance
- Internal oil leakage
- Clogged oil passages
- Failed oil-pressure control valve
- Damaged oil-pump drive
Low oil pressure can affect:
- Camshaft phasers
- Timing-chain tensioners
- VVT solenoids
- Camshaft timing stability
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:
- Sludge
- Metal debris
- Varnish
- Internal wear
- Damaged spool valve
- Weak return spring
- Electrical malfunction
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:
- Sludge
- Carbon
- Metal particles
- Gasket material
- Silicone sealant
- Oil-filter debris
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:
- Sludge
- Varnish
- Excessive sealant
- Debris
- Damaged gasket
- Incorrect cylinder-head assembly
- Previous engine repairs
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:
- Stick advanced
- Fail to lock at startup
- Leak internally
- Move inconsistently
- Rattle during startup
- Develop excessive play
- Respond slowly
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:
- Startup rattle
- Multiple camshaft codes
- Poor performance
- Extended cranking
- Excessive tensioner extension
- Correlation codes such as P0018
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:
- Failed tensioner
- Broken timing guide
- Missing belt teeth
- Severe chain wear
- Incorrect installation
- Engine kickback during starting
A severely jumped timing system may cause:
- Rough running
- Low compression
- No-start condition
- Valve damage
- Piston damage
11. Incorrect Mechanical Timing
P0021 may appear immediately after:
- Timing-chain replacement
- Timing-belt replacement
- Camshaft replacement
- Camshaft-phaser replacement
- Cylinder-head repair
- Engine rebuilding
Possible mistakes include:
- Bank 2 intake camshaft one tooth off
- Incorrect timing marks
- Wrong chain-link alignment
- Phaser installed in the wrong position
- Tensioner released incorrectly
- Incorrect locking-tool procedure
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:
- Weak signal
- Signal dropout
- Distorted waveform
- Heat-related failure
- Metal debris on the sensor
- Incorrect air gap
- Internal electrical failure
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:
- Loose
- Bent
- Cracked
- Misaligned
- Shifted
- Damaged during repairs
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:
- Broken wires
- Short to ground
- Short to voltage
- Corroded terminals
- Loose connectors
- Oil contamination
- Heat damage
- Harness abrasion
- Poor previous repairs
Electrical circuit problems may also store P0020.
15. Faulty ECM or PCM
ECM failure is uncommon but possible.
A damaged internal driver may:
- Command the solenoid continuously
- Fail to release the actuator
- Produce an incorrect duty cycle
- Misinterpret camshaft-position data
Before replacing the ECM, verify:
- Solenoid operation
- Wiring integrity
- Oil pressure
- Camshaft sensor signal
- Mechanical timing
- Phaser condition
16. Incorrect Replacement Components
Incorrect replacement parts may cause P0021.
Examples include:
- Wrong VVT solenoid
- Incorrect camshaft phaser
- Wrong timing chain
- Incorrect sprocket
- Nonmatching camshaft
- Low-quality aftermarket components
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:
- Hydraulic
- Mechanical
- Electrical
- Software-related
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:
- Continued misfires
- Poor fuel economy
- Increased emissions
- Catalytic converter damage
- Timing-chain wear
- Timing-system failure
- Valve-to-piston contact
- Bent valves
- Damaged pistons
- Complete engine failure
The code becomes especially serious when accompanied by:
- Timing-chain rattle
- Low-oil-pressure warning
- P0018
- Severe misfires
- Flashing Check Engine Light
- Engine stalling
- No-start condition
Can You Drive With P0021?
Limited driving may be possible if:
- The engine runs smoothly.
- No timing noise is present.
- The oil level is correct.
- Oil pressure is normal.
- The Check Engine Light remains steady.
- The vehicle does not stall.
Continued driving is not recommended until the cause is known.
Stop driving immediately if you notice:
- Loud timing-chain rattle
- Severe engine misfires
- Flashing Check Engine Light
- Sudden power loss
- Engine stalling
- Backfiring
- Low-oil-pressure warning
- Engine cranks but will not start
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:
- P0008
- P0009
- P0018
- P0020
- P0022
- P0023
- P0024
- P0025
- Camshaft sensor codes
- Crankshaft sensor codes
- Misfire codes
- Oil-pressure codes
Record:
- Freeze-frame data
- Engine speed
- Engine load
- Coolant temperature
- Oil temperature
- Commanded camshaft angle
- Actual camshaft angle
- VVT solenoid duty cycle
- Battery voltage
Do not clear the codes before recording this information.
Step 2: Confirm Bank 2 and Camshaft A
Use vehicle-specific service information to identify:
- Bank 2
- Intake camshaft
- Camshaft A
- Bank 2 intake VVT solenoid
- Camshaft phaser
- Camshaft position sensor
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:
- Low level
- Overfilled crankcase
- Fuel dilution
- Coolant contamination
- Metallic particles
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:
- Dirty
- Sludged
- Too thick
- Too thin
- Incorrect for the engine
- Overdue for replacement
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:
- When the oil was last changed
- Whether the engine has been run low on oil
- Whether timing work was recently completed
- Whether the engine rattles during startup
- Whether the timing belt is overdue
- Whether the phaser or solenoid was recently replaced
- Whether engine sealant was used excessively
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:
- Broken wires
- Chafed insulation
- Loose connectors
- Corrosion
- Bent pins
- Oil contamination
- Heat damage
- Harness abrasion
- Poor previous repairs
Repair electrical faults before condemning mechanical components.
Step 7: Test the Bank 2 Intake VVT Solenoid Electrically
Test the solenoid for:
- Resistance
- Power supply
- ECM control
- Short to ground
- Short to voltage
- Excessive circuit resistance
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:
- Commanded camshaft angle
- Actual camshaft angle
- Response time
- Solenoid duty cycle
- Engine idle quality
Possible results include:
- No response: Electrical fault, blocked oil passage, failed solenoid or failed phaser
- Slow response: Dirty oil, restricted passage or worn phaser
- Camshaft remains advanced: Sticking solenoid, trapped oil or failed phaser
- Erratic response: Oil-pressure problem, sensor fault or mechanical wear
Step 9: Remove and Inspect the VVT Solenoid
Remove the Bank 2 intake VVT solenoid according to the service procedure.
Inspect for:
- Sludge
- Varnish
- Metal debris
- Clogged screens
- Damaged O-rings
- Sticking spool valve
- Physical damage
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:
- Resistance
- Current draw
- Physical condition
- Scan-tool response
- Contamination
Some technicians temporarily swap identical solenoids between banks.
Only do this when:
- The part numbers match.
- The manufacturer permits it.
- The components are clean.
- New seals are installed if required.
If the fault moves to Bank 1, the solenoid is likely defective.
Step 11: Monitor Camshaft Position Data
Compare:
- Commanded Bank 2 intake camshaft position
- Actual Bank 2 intake camshaft position
- Bank 1 intake camshaft position
- Phase error
- VVT duty cycle
If Bank 1 responds normally while Bank 2 remains advanced, suspect a Bank 2-specific problem.
Possible causes include:
- Bank 2 VVT solenoid
- Bank 2 oil passage
- Bank 2 phaser
- Bank 2 sensor
- Bank 2 mechanical timing
Step 12: Check Engine-Oil Pressure
Install a mechanical oil-pressure gauge if pressure problems are suspected.
Measure pressure at:
- Cold idle
- Warm idle
- Increased engine speed
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:
- Power supply
- Ground
- Signal voltage
- Signal frequency
- Waveform quality
- Circuit continuity
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:
- Bank 2 intake camshaft signal
- Crankshaft position signal
Compare the waveform with known-good data.
This may reveal:
- Timing-chain stretch
- Incorrect mechanical timing
- Shifted reluctor wheel
- Sensor dropout
- Excessive camshaft movement
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:
- Startup rattle
- Excessive internal movement
- Failure to lock
- Slow response
- Camshaft stuck advanced
- Metal debris in oil
- Repeated P0021 after solenoid replacement
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:
- Valve covers
- Timing covers
- Engine accessories
- Engine mounts
- Camshaft access plugs
Position the engine at top dead center and inspect:
- Timing-chain alignment
- Timing-belt alignment
- Sprocket marks
- Chain tensioner extension
- Guide condition
- Camshaft phaser position
- Crankshaft alignment
- Bank 2 intake camshaft alignment
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:
- Shifted position
- Cracks
- Bent targets
- Loose mounting
- Damage
- Incorrect installation
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:
- Updated VVT solenoids
- Revised camshaft phasers
- Timing-chain stretch
- Oil-pressure concerns
- Restricted oil passages
- Updated oil specifications
- ECM software updates
- Revised repair procedures
Review manufacturer information before performing major repairs.
Step 19: Verify the Repair
After completing repairs:
- Clear stored codes.
- Start the engine from cold.
- Listen for timing-system noise.
- Monitor commanded and actual camshaft position.
- Command the VVT system with a scan tool.
- Check for oil leaks.
- Complete the manufacturer’s drive cycle.
- 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
| Repair | Estimated 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:
- Engine design
- Component accessibility
- Number of timing chains
- Whether the engine must be removed
- Whether both banks require repair
- Whether internal engine damage occurred
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:
- A stretched timing chain
- Failed phaser
- Broken timing guide
- Jumped timing belt
- Shifted reluctor
- Incorrect mechanical timing
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:
- Failed phaser lock pin
- Timing-chain slack
- Tensioner drain-down
- Worn guides
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:
- Oil contamination
- Solenoid failure
- Phaser failure
- Timing-chain wear
- Wiring faults
- Incorrect mechanical timing
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:
- Ford
- Lincoln
- Chevrolet
- GMC
- Buick
- Cadillac
- Chrysler
- Dodge
- Jeep
- Toyota
- Lexus
- Nissan
- Infiniti
- Hyundai
- Kia
- BMW
- Mini
- Mercedes-Benz
- Volkswagen
- Audi
- Porsche
- Subaru
- Volvo
- Mitsubishi
P0021 is commonly associated with engines using:
- V6 or V8 layouts
- Dual-overhead camshafts
- Hydraulic timing-chain tensioners
- Intake camshaft phasers
- Oil-controlled VVT solenoids
- Separate camshaft sensors for each bank
The code alone does not prove that a particular model has a known defect.
Diagnosis must be based on the exact:
- Year
- Make
- Model
- Engine
- Maintenance history
- Repair history
How to Prevent P0021
Helpful preventive measures include:
- Check the engine oil regularly.
- Use the manufacturer-specified oil viscosity.
- Change the oil and filter on schedule.
- Avoid extended oil-change intervals.
- Use a quality oil filter.
- Repair oil leaks promptly.
- Investigate excessive oil consumption.
- Address startup rattles immediately.
- Diagnose low-oil-pressure warnings promptly.
- Replace timing belts at the required interval.
- Use correct timing tools during repairs.
- Keep VVT oil passages free of excessive sealant.
- Replace damaged connectors and wiring.
- Use the correct VVT solenoid and camshaft phaser.
- Verify all timing marks after engine repairs.
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:
- Dirty or incorrect engine oil
- Low oil level
- Low engine-oil pressure
- A sticking Bank 2 intake VVT solenoid
- Restricted oil passages
- A failed intake camshaft phaser
- A stretched or jumped timing chain
- Incorrect mechanical timing
- A faulty camshaft sensor
- A shifted reluctor wheel
- Damaged wiring or connectors
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.
For more diagnostic guides, browse our growing OBD-II libraries:
- Complete OBD-II Code Library: https://my.prostreetonline.com/dtc-obdii/
- Body (B) Codes: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
- Chassis (C) Codes: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/
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