What P0021 means
The engine control module compares the commanded position of the intake camshaft on bank 2 with the actual position it calculates from the camshaft and crankshaft sensors.
How the engine computer detects it
This code is set when the camshaft sits further advanced than commanded for longer than a calibrated time, or, depending on the manufacturer, when the target is missed in either direction ("system performance"). Typical cause is a phaser that does not return to its rest position, for example because the oil control valve sticks open or its screen is clogged. Bank 2 exists only on V and boxer engines; it is the cylinder bank without cylinder 1.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Rough or unstable idle, as valve overlap is too large
- Engine may stall at idle
- Rattling from the timing drive at cold start
- Higher fuel consumption
Common causes
- Oil level too low, oil sludged or wrong viscosity Most likely
- Screen at the oil control valve clogged with debris Most likely
- Oil control valve mechanically sticking Most likely
- Cam phaser worn or its locking pin sticking Possible
- Timing chain worn or fitted incorrectly after a repair Less likely
How to diagnose P0021
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: cam phaser intake bank2, oil control valve intake bank2, engine oil, timing chain.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0021 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Subaru Impreza | 2006–2014 | 5 | 129k | |
| Chevrolet Traverse | 2018 | 3 | 10k | |
| Hyundai Santa FE | 2016–2017 | 3 | — |
Counts of owner complaints to the NHTSA that mention P0021 (29 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 0
- Fuel and air metering, auxiliary emission controls
- 21
- Specific fault
Questions drivers ask
Can I drive with code P0021?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0021?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0021 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0021 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0021. They can point to a shared cause, so it's worth checking them together.
- P0011"A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)12 complaints
- P0014"B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)5 complaints
- P0018Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)5 complaints
- P0024"B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)4 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.