TSB: Some Prius, Prius V, and Prius PHV vehciles may exhibit a rough idle or tapping noise from the HV transaxle at cold start. The Check Engine Light may also illuminate with (DTC) P0401 (Exhaust Gas Recirculation Flow Insufficient Detected). Due to excess carbon build-up at the valve assembly, the valve will stick, causing the engine RPM to fluctuate. Follow the procedures in this bulletin to address the condition.
