Advanced Diagnostics

DTC P2651: Rocker Arm Oil Pressure Switch B Circuit Low Voltage (PZEV Model)









General Description

The VTEC system activates the rocker arm oil control solenoid B by command from the powertrain control module (PCM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that switches valve timing between Low and High. The PCM monitors oil pressure in the hydraulic circuit of the VTEC mechanism using the rocker arm oil pressure switch B downstream of the rocker arm oil control solenoid B. If there is a difference between the oil pressure condition in the hydraulic circuit that is determined by the PCM command and the oil pressure condition that is determined by the status of the rocker arm oil pressure switch B, the system is considered faulty, and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold

When the rocker arm oil control solenoid B is ON, the rocker arm oil pressure switch B remains ON.

Confirmation Procedure with the HDS

Do the VTEC TEST in the INSPECTION MENU with the HDS.

Driving Pattern

1. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on.
2. Then, engine speed 3,500 rpm or more for at least 10 seconds.

- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for illuminating the MIL
When a malfunction is detected during the first drive cycle, a Temporary DTC is stored in the PCM memory. If the malfunction recurs during the next (second) drive cycle, the MIL comes on and the DTC and the freeze frame data are stored.

Conditions for clearing the MIL
The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the diagnostic runs.The MIL, the DTC, the Temporary DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by disconnecting the battery.