P0021: "A" camshaft position timing over-advanced or system performance (bank 2)

How to read it

P0021 is one of the standard OBD-II trouble codes stored when the check engine light comes on. SAE J2012, the standard that defines the codes, names it ““A” Camshaft Position – Timing Over-Advanced or System Performance Bank 2”; a Subaru service bulletin gives the same name.

Also searched as: code P0021, P0021 code.

What the monitor checks

The federal rule’s catch-all covers any other electronic powertrain component that sends input to or takes commands from the on-board computer and has a measurable effect on emissions.

Look-alikes

P0011: "A" camshaft position timing over-advanced or system performance (bank 1) is the same fault on bank 1.

What the manual says to do

Ford’s F-150 manual says that if the indicator stays on, the vehicle should be serviced at the first available opportunity, and that continued driving with it on can mean higher emissions, lower fuel economy, rougher running and more costly repairs.

How the light goes out

Under the federal rule, the check engine light may go out once the fault has not come back during three trips in a row in which its monitor runs without finding it. The system may erase the stored code if the same code has not been registered again in at least 40 engine warm-up cycles.