The P0021 fault code, applicable to all car manufacturers, means “A Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)“.
Background Information: The camshaft controls the opening and closing of the valves. In a variable valve timing system, the electronic camshaft adjusting valve (or oil control valve, OCV) adjusts the camshaft angle by changing the oil pressure to the camshaft adjuster (mechanical) according to instructions from the engine control module (ECM), ensuring the valves open and close at the optimal time. Causes of the P0021 fault include incorrect timing of the intake/left/front camshaft, mechanical jamming of the camshaft due to over-timing, or the actuator valve being stuck in the open position. In short, it’s either timing too early or system performance issues. “A” camshaft must refer to the “intake,” “left,” or “front” camshaft. Determine left/right and front/rear from the driver’s position with a forward view. The first group refers to the bank of cylinders including cylinder 1, and the second group is the group opposite the first group.
Tip: To quickly find fault codes, you can use a professional OBD scanner. This will help you accurately pinpoint the problem. This data can help you understand the performance of various vehicle components and troubleshoot before the problem worsens.