# P0021: "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 2) **Verdict:** Drive to a shop this week Camshaft timing - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $80-$3,000 - **Urgency:** This week - **Most likely:** Oil problem or bank 2 intake cam solenoid - **DIY?:** Steps 1-4 ## Quick answer P0021 means the engine computer found the bank 2 "A" camshaft, the intake cam on most engines, too far advanced or not following its commands. It only applies to engines with two cylinder banks. Low or dirty oil and a sticking bank 2 cam timing solenoid are the most common causes. ## What does P0021 mean? On a V6 or V8 with variable valve timing, each bank has its own intake cam phaser and oil control solenoid. The engine computer pulses the solenoid to send oil to one side of the phaser or the other, twisting the cam ahead (advance) or back (retard) to suit speed and load. It checks the result with the bank 2 intake cam position sensor many times a second. P0021 sets when the actual bank 2 intake cam angle is ahead of the commanded angle by too much, or does not follow commands closely enough, for a calibrated time. That is why the title includes both "over-advanced" and "system performance". Many makers need two trips. "A" means intake, left or front under SAE J2012, and bank 2 is the side without cylinder 1. P0011 is the same check on bank 1. ## What are the symptoms of P0021? - Check engine light on - Rough or uneven idle once warm - Hesitation or flat acceleration from a stop - Occasional stalling at idle - Lower fuel economy ## What causes P0021? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Low, dirty or wrong-grade engine oil** (most common). Both banks share the same oil, so an oil problem often sets P0021 together with P0011. Sludge, a low level or a viscosity other than the one specified makes the phaser slow or erratic, and it may overshoot when it finally moves. Engines that run low between changes or go long intervals are most at risk. 2. **Sticking bank 2 intake cam solenoid** (common). If P0021 sets without P0011, the bank 2 solenoid becomes the leading suspect. A spool stuck partly open keeps feeding the advance side of the phaser. On many engines the bank 1 and bank 2 solenoids are the same part, so swapping them and seeing whether the code moves to P0011 is a simple, free test. 3. **Worn bank 2 intake cam phaser** (less common). Worn vanes or seals inside the phaser let oil bypass, so the cam drifts or overshoots instead of holding its angle. A lock pin that does not engage at shutdown can also cause a brief clatter on startup. On the rear bank of transverse engines, phaser replacement is labor-heavy because access is so limited. 4. **Clogged oil screen at the bank 2 solenoid** (less common). Some V engines use a small filter screen in the oil passage that feeds each bank's solenoid. Debris from sludge or a failed chain guide can clog the bank 2 screen, giving that phaser a poor oil supply while bank 1 works normally. Removing the solenoid and inspecting the port often reveals it. 5. **Bank 2 cam timed wrong or chain problem** (rare). A cam installed a tooth off, or worn timing parts, can shift the bank 2 baseline so the computer sees a cam angle it cannot reconcile with its command. This usually brings correlation codes such as P0018 too. When P0021 appears alone on a quiet engine with good oil, the chain is unlikely to be the cause. ## How do you diagnose P0021? 1. Check the oil level and condition, and confirm the grade matches the owner's manual. 2. Read all codes; P0021 with P0011 suggests oil, while P0021 alone points to bank 2 parts. 3. Compare desired and actual bank 2 intake cam angle on a scan tool during a test drive, or command the solenoid. 4. Swap identical bank 1 and bank 2 solenoids, if the maker allows it, and see whether the code moves to P0011. 5. Inspect the bank 2 solenoid port and any oil screen for sludge or debris. ## How do you fix P0021, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Oil and filter change | $80-$150 | Use the exact viscosity and specification listed for the engine. | | Replace bank 2 intake cam solenoid | $150-$500 | Rear-bank solenoids on some transverse V6 engines take longer to reach. | | Replace bank 2 intake cam phaser | $1,000-$3,000 | Requires timing cover or chain work on many V engines. | Full price breakdowns: [oil change cost](/cost/oil-change), [timing chain replacement cost](/cost/timing-chain-replacement). ## Is it safe to drive with P0021? > **Drive to a shop this week.** Usually safe for short, gentle trips while you arrange a repair, as long as the oil level is correct. Stop and have it towed if a loud rattle appears, the engine stalls repeatedly or the check engine light flashes, which signals a misfire. ## Will P0021 fail an emissions test? P0021 keeps the check engine light on and will fail an OBD-II emissions test in most states. Variable valve timing also helps control emissions, so the car may run dirtier until it is fixed. After clearing the code, allow several days of mixed driving for the readiness monitors to complete before going back for a test. ## After the repair: clearing P0021 Clear the code and take a test drive with a scan tool showing desired and actual bank 2 intake cam angle; they should follow each other closely during acceleration and cruising. The idle should be steady once warm. If no pending code appears after several days of mixed driving, the repair worked. ## How to prevent P0021 - Check the oil level every few fill-ups on V6 and V8 engines that tend to use oil. - Stick to the oil viscosity listed for your engine, because the cam timing calibration assumes it. - Change oil sooner with mostly short trips or extreme heat to keep sludge from forming. - Fix oil leaks promptly so the level never drops low enough to starve the phasers. ## Codes often seen with P0021 - [P0011](/codes/p0011): "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1) - [P0018](/codes/p0018): Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A) - [P0012](/codes/p0012): "A" Camshaft Position - Timing Over-Retarded (Bank 1) - [P0014](/codes/p0014): "B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1) - [P0010](/codes/p0010): "A" Camshaft Position Actuator Circuit (Bank 1) ## Frequently asked questions ### Can I drive with a P0021 code? Yes, for short, gentle trips in most cases, once you have confirmed the oil is full. Idle and low-speed response may be rough. Stop and get help if the engine stalls repeatedly, a heavy rattle starts from the timing area, or the check engine light starts flashing. ### What is the most common cause of P0021? Low, dirty or wrong-grade oil is the most common cause of P0021, because the cam phaser moves on oil pressure. A sticking bank 2 intake cam solenoid is next. Worn phasers, clogged oil screens and timing problems are less common, so start with the oil and the solenoid. ### What is the difference between P0011 and P0021? P0011 is the bank 1 intake cam timing code and P0021 is the same fault on bank 2. When both appear, the cause is usually shared, such as oil condition. When only P0021 sets, focus on bank 2 parts like its solenoid, its oil screen or its phaser. ### How much does it cost to fix P0021? Most P0021 repairs cost $80 to $3,000 at an independent shop. An oil and filter change runs $80 to $150 and a bank 2 intake cam solenoid $150 to $500. A bank 2 intake cam phaser costs $1,000 to $3,000 because of the labor needed on many V engines. ### Where is bank 2 on my engine? Bank 2 is the cylinder bank that does not contain cylinder 1. On a transverse V6 it may be the front or the rear bank, depending on the maker. Check service information or a repair manual for your engine's cylinder numbering before replacing any bank 2 solenoid or sensor. ### Can a bad cam solenoid cause P0021? Yes, a bank 2 intake cam solenoid stuck partly open is a common cause of P0021. It keeps sending oil to the advance side of the phaser. A scan tool test that commands the solenoid, or swapping it with an identical bank 1 solenoid, shows whether it is at fault. ### Will an oil change fix P0021? An oil change can fix P0021 when the oil was low, sludged, overdue or the wrong viscosity. Use the exact grade listed for your engine, clear the code and drive for several days. If P0021 returns, test the bank 2 solenoid and inspect its oil screen next. ### Can I fix P0021 myself? You can often handle the oil change and, on many engines, the bank 2 solenoid yourself. Front-bank solenoids are usually easy to reach, while rear-bank ones may need parts removed first. Phaser replacement requires cam locking tools and correct timing, so most owners leave it to a shop. ### Is P0021 serious? P0021 is moderately serious. It usually does not damage the engine right away, and many engines fall back to a safe cam position. But driving with low or sludged oil, a common cause, can wear the engine quickly. Have it diagnosed within a week or two. ### Why does P0021 set only when the engine is warm? Warm oil is thinner and gives less pressure at idle, so a weak phaser, a sticking solenoid or a partly clogged screen shows up more once the engine is hot. Worn-out or wrong-viscosity oil makes this worse. A cold engine with thicker oil can mask the problem. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) - [fueleconomy.gov: Keeping your vehicle in shape](https://www.fueleconomy.gov/feg/maintain.jsp) ## Other camshaft timing codes - [P0011 "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)](https://diagxcar.com/codes/p0011) - [P0012 "A" Camshaft Position - Timing Over-Retarded (Bank 1)](https://diagxcar.com/codes/p0012) - [P0013 "B" Camshaft Position Actuator Circuit (Bank 1)](https://diagxcar.com/codes/p0013) - [P0014 "B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)](https://diagxcar.com/codes/p0014) - [P0015 "B" Camshaft Position - Timing Over-Retarded (Bank 1)](https://diagxcar.com/codes/p0015) - [P0016 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)](https://diagxcar.com/codes/p0016) - [P0017 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)](https://diagxcar.com/codes/p0017) - [P0018 Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)](https://diagxcar.com/codes/p0018) - [P0019 Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor B)](https://diagxcar.com/codes/p0019) - [P0030 HO2S Heater Control Circuit (Bank 1 Sensor 1)](https://diagxcar.com/codes/p0030) ## Symptoms - [Why is my car idling rough?](https://diagxcar.com/symptoms/rough-idle) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) - [Why is my car getting bad gas mileage?](https://diagxcar.com/symptoms/poor-gas-mileage) ## Repair costs - [Oil change cost](https://diagxcar.com/cost/oil-change): $45-$150 - [Timing chain replacement cost](https://diagxcar.com/cost/timing-chain-replacement): $1,200-$3,500 --- Source page: https://diagxcar.com/codes/p0021 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.