P0021 code definition
Camshaft Position A - Timing Over-Advanced or System Performance (Bank 2)
What the P0021 code means
P0021 is the OBD-II generic code indicating that the Engine Control Module (ECM) has determined that the bank 2 intake camshaft is more advanced than what the ECM has commanded it to be. This over advanced condition could be during advancing, or retarding of the camshaft timing.
What causes the P0021 code?
The camshaft is more advanced than the ECM has commanded it to advance.
The camshaft is more advanced when it has been commanded to retard to a lower timing level.
The Oil Control Valve (OCV) connected to the bank 2 camshaft may be stuck or have clogged oil passages.
The oil is too thick, causing the passages to become clogged. This can be from the wrong oil or lack of oil changes.
The camshaft phaser is stuck in the advanced position.
What are the symptoms of the P0021 code?
The ECM will turn on the Check Engine Light.
The engine may idle normally but can hesitate or stall on acceleration.
A reduction in fuel mileage may happen due to the camshafts not being at an optimal position.
The engine emissions may exceed federal levels.
Note: The symptoms may change depending on the camshaft timing positions when the camshaft stopped advancing or retarding.
How does a mechanic diagnose the P0021 code?
Visually inspects for damaged wiring or connectors
Checks the engine for sludge and for the engine to be full of clean engine oil with the correct viscosity
Scans and documents the codes then views the freeze frame data to see when the code was set
Clears the OBD-II fault codes and retests the vehicle to see if the P0021 code comes back
Performs the manufacturer's pinpoint tests for the P0021 code
Note: The manufacturer's pinpoint test will be different for different engines and year of manufacturer.
Common mistakes when diagnosing the P0021 code
Follow these simple guidelines to help prevent misdiagnosis:
Do a visual inspection for problems, like checking to see if all electrical connectors are connected, or harness is damaged.
Check engine oil to see if it is full, clean and of the correct viscosity.
Verify the failure code is active by clearing and retesting the code.
Follow pinpoint tests step-by-step without skipping any steps.
How serious is the P0021 code?
The engine may run erratically and have various drive complaints that could cause unsafe driving conditions if the engine hesitates or stalls.
The fuel consumption may increase and carbon fouling of engine components may occur.
What repairs can fix the P0021 code?
Clearing the Check Engine Light codes and road testing to verify the code
Changing the oil and filter to the proper oil viscosity for the engine specifications
Repairing or replacing the wiring to the camshaft oil control valve for bank 2 intake camshaft
Replacing the camshaft oil control valve for bank 2 intake camshaft
Checking the timing chain and camshaft phasers
Additional comments for consideration regarding the P0021 code
The engine oil passages through the camshafts; the oil control valves are of small size and require only the manufacturer's recommended oil viscosity to be used. If the oil is sludged up or an oil with a higher viscosity is in the engine, then it could cause the camshaft VVT to not work as designed.
Need help with a P0021 code?
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This article originally appeared on YourMechanic.com as P0021 OBD-II Trouble Code: Camshaft Position A - Timing Over-Advanced or System Performance (Bank 2) and was authored by Jay Safford.