Possible causes

– Faulty Intake Valve Timing Control Solenoid Valve
– Intake Valve Timing Control Solenoid Valve harness is open or shorted
– Intake Valve Timing Control Solenoid Valve circuit poor electrical connection
– Faulty Camshaft Position Sensor
– Camshaft Position Sensor harness is open or shorted
– Camshaft Position Sensor circuit poor electrical connection
– Faulty Crankshaft Position Sensor (POS)

Tech notes

Since the Intake valve timing control solenoid valve uses oil flow to control timing, dirty oil can cause the valve to stuck open or close. Before replacing the valve, change engine oil and filter and reset engine code.

When is the code detected?

When there is a gap between angle of target and phase-control angle degree, the valve will stop working and the ECM will trigger the P0021 code.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Lack/Loss of power
– Engine rough idle

P0021 NISSAN ALTIMA SEDAN Description

This mechanism hydraulically controls cam phases continuously with the fixed operating angle of the intake valve.

The ECM receives signals such as crankshaft position, camshaft position, engine speed, and engine coolant temperature. Then, the ECM sends ON/OFF pulse duty signals to the intake valve timing control solenoid valve depending on driving status. This makes it possible to control the shut/open timing of the intake valve to increase engine torque in low/mid speed range and output in high-speed range.

The intake valve timing control solenoid valve changes the oil amount and direction of flow through intake valve timing control unit or stops oil flow. The longer pulse width advances valve angle. The shorter pulse width retards valve angle. When ON and OFF pulse widths become equal, the solenoid valve stops oil pressure flow to fix the intake valve angle at the control position.