P2021 indicates that the engine control module has detected a low voltage condition in the intake manifold runner position sensor/switch circuit for Bank 2. This usually means the sensor signal is below the expected threshold, which can affect the variable intake runner system and engine performance.
The sensor itself may have an internal short or open circuit, causing its output voltage to drop below the PCM's expected range.
Damaged, chafed, or corroded wires in the sensor circuit can pull the signal low or interrupt it entirely.
Moisture ingress or vibration can degrade the connector pins, increasing resistance and lowering the sensed voltage.
If the actuator mechanism is stuck, it may prevent the sensor from moving properly, resulting in a persistently low signal.
A rare internal fault in the PCM's sensor input circuit can cause a low reading; this is considered only after wiring and sensor checks.
No. The PCM is rarely the cause; most P2021 cases are due to sensor failure, wiring issues, or connector problems. PCM replacement should be considered only after those components have been tested and found good.
Not directly. The code relates to the sensor circuit, not manifold cleanliness, although excessive carbon buildup could impede actuator movement and indirectly affect sensor readings.
Clearing the code only turns off the Check Engine Light temporarily. If the underlying fault remains, the code will return after the next drive cycle.