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This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


The P0021 OBD-II trouble code means “A” camshaft position timing is over advanced (above a set limit) in bank 2 than what the ECM has commanded it to be.


The variable camshaft timing (VCT) or variable valve timing (VVT) system increases fuel economy and engine performance by regulating when the intake and exhaust valves are opened and closed. The camshafts are adjusted by the ECM with the help of oil control valves (OCV) also known as variable valve timing control solenoid valves. When the diagnostic trouble code P0021 is set, it means that the intake camshaft in Bank 2 is more advanced than the ECM has instructed it to be.

In this respect, if the cam timing is over advanced (above a set limit), the engine light will be illuminated and the code will be set. The “A” camshaft refers to either the intake, left, or front camshaft. This OBD-II diagnostic code is similar to P0011, the only difference lies in that P0021 specifies that it is for bank 2


An OBD-II error code P0021 means that one or more of the following issues has occurred:

  • Faulty intake valve timing control solenoid valve
  • Poor electrical connection of  variable valve timings control solenoid valves circuit 
  • Harness issue in the variable valve timings control solenoid valves 
  • The camshaft has advanced further than the ECM instructed it to  
  • The camshaft is more advanced when it has been directed to retard to a lower timing level
  • Camshaft phaser stuck at an advanced angle
  • The oil control valve connected to the bank 2 camshaft have clogged oil passages or

might be stuck

  • The oil is too thick which can clog the passages,  this can be due to the wrong oil/dirty oil or lack of oil changes.
  • Electrical connections are damaged or shorted

Faulty crankshaft position sensor             


Below mentioned are the common symptoms related to OBD error code P0021:

  • The check engine light will turn ON
  • The engine may idle normally, but can delay or slow down on acceleration.
  • A decrease in fuel mileage may occur because of the camshafts not being at an optimal position.
  • Engine contamination
  • If the actual solenoid does fail, this will cause a retardation in the intake valve activity
  • Possibly camshaft failure because of lack of lubrication

Note: The symptoms may vary  depending on the camshaft timing positions when the camshaft stops advancing or retarding.


In order to diagnose OBD error code P0021, you will need an OBD-II scanner, multimeter

hand tools, manufacturer’s vehicle manual, and cleaning rags

  • Firstly, use the OBD-II scanner to double-check the code. Then, clear the code.
  • Use a multimeter to examine the terminals for solenoid failure. Check the multimeter for an ohm reading and ensure it lies between 7-12 which is the ideal range, if it is off the range then the solenoid most likely needs to be replaced.
  • Run a pin test between the solenoid and the ECM before making any repairs, visually inspect for damaged wires or connectors at the sensors
  • Check the engine for sludge and the engine to be fully filled with clean engine oil of correct viscosity.
  • Scan with the OBD-II scanner again to accumulate freeze-frame data to acknowledge when the code was triggered. After collecting data, clear the code and retest the vehicle to check if the code sets.
  • Run through the manufacturer’s pinpoint tests.
  • Use hand tools to screw up harness terminals at the solenoid, use the rag when needed to clean the terminals. Lubricate the contacts with grease for optimal electric contact. Change the solenoids if necessary.
  • Change the engine oil and filter using the manufacturer’s recommended viscosity range of the oil.
  • Use the hand tools to repair or replace wiring on the bank-2 camshaft control valve. If necessary, replace the camshaft in bank 2. Also, inspect the timing chain and repair or replace if needed.

Common mistakes

This code can be mistakenly determined if you do not follow the right diagnostic procedure. Follow these simple guidelines to help prevent misdiagnosis:

  • Visually inspect electrical connections for damage
  • Inspect the engine oil for the correct viscosity
  • Reset and retest the OBD-2 code
  • Go through the manufacturer’s pinpoint test exactly without skipping any steps

How serious is this?

The OBD-II code P0021 is moderately serious. When the engine slows down or delays, the passengers are in an unsafe condition. The vehicle may utilize more fuel than normal, which can create environmental problems in the future. Carbon fouling in the engine can also happen with excess top fuel use.

What repairs can fix the code?

repair manuals

  • Clear the check engine light codes and test drive to verify the code
  • Changing the oil and filter to the correct oil viscosity level as per the manufacturer’s specifications
  • Repair or replace the wiring of the camshaft oil control valve for bank 2 intake camshaft
  • Replace the camshaft oil control valve for bank 2 intake camshaft
  • Check the timing chain and camshaft phasers.

Related codes

P0011 – Intake Camshaft Position Timing – Over-Advanced (Bank 1)

P0016 – Crankshaft Position – Camshaft Position Correlation – Bank 1 Sensor A

P0018Crankshaft Position – Camshaft Position Correlation – Bank 2 Sensor A

P0022 – Intake Camshaft Position Timing – Over-Retarded (Bank 2)

P0171 – System Too Lean (Bank 1)

P0174 – System Too Lean (Bank 2)


The OBD-II scanner error code P0021 severely impacts the drivability of your vehicle. The engine may run erratically and have different drive complaints that could cause unsafe driving conditions if the engine delays or slow down.  The most common problems consist of increased engine stalling, engine rough idle, decrease in fuel economy, and rattling/knocking noises from the engine. 

To avoid triggering the P0021 code, there are few steps to take into consideration. The first step is to ensure the correct engine oil usage with the correct viscosity level as recommended in the manufacturer’s vehicle manual. The next step you can take is to avoid driving on bumpy roads as much as possible to keep the wiring intact. Additionally, follow the manufacturer’s recommendations for routine maintenance.