Honda P2647 VTEC System Stuck ON
Honda service bulletin 13-021
Honda has issued a service bulletin 13-021 to address several trouble codes related to the VTEC system on the vehicles listed below. The trouble codes are:
• P2646/P2651 (rocker arm oil pressure switch circuit low voltage).
• P2647/P2652 (rocker arm oil pressure switch circuit high voltage).
Honda has determined that the rocker arm oil pressure switch may fail intermittently
Vehicles affected by Honda 13-021 service bulletin
2003–12 Accord L4
2012–13 Civic ALL except Si and Hybrid ALL
2002–05 Civic Si
How the Honda VTEC system works
The Honda variable cylinder management (VCM) system activates the rocker arm oil control solenoid (VTEC solenoid valve) when commanded by the powertrain control module (PCM). When operated, it either charges or discharges the hydraulic circuit of the cylinder pause VTEC system. The PCM monitors oil pressure in the hydraulic circuit of the VTEC mechanism using the engine oil pressure (EOP) sensor downstream of the rocker arm oil control solenoid (VTEC solenoid valve). If the PCM sees a difference between the oil pressure condition in the hydraulic circuit the system is considered faulty, and a DTC is stored.
Diagnose and fix Honda P2647, P2646, P2651, P2652
The Variable Timing/Lift Control (VTEC) oil pressure switch is located on the back of the cylinder block near the oil filter.
The VTEC oil pressure switch has a Blue/Black (BLU/BLK) wire. The switch is normally closed, so it grounds the reference voltage from the PCM when the key is in the RUN position. The PCM monitors the voltage drop to confirm that the switch is closed and grounded.
When the engine RPMs reach about 2,700 while driving, the PCM energizes the VTEC solenoid that allows oil pressure to flow into the intake valve rocker arms. The VTEC oil pressure switch senses the change in oil pressure and opens. The ECM sees the voltage rise, confirming that the switch is no longer grounded.
The trouble code will set if the VTEC oil pressure switch is not grounded when engine RPMs are below 2,700 and will also set a code if the oil pressure switch does not open at RPMs above 3,000.
If the code sets at 2700 RPMs or higher, start by
checking engine oil level. If it’s low, top off the oil, clear the code, and take the vehicle for a test drive. If the code reappears, replace the oil pressure switch with Honda switch 37250-PNE-G01 and O-ring 91319-PAA-A01
©, 2021 Rick Muscoplat
Posted on by Rick Muscoplat