Advanced Diagnostics

Advanced Diagnostics - DTC P2646: VTEC System Stuck OFF











General Description
The VTEC system activates the rocker arm oil control solenoid 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 sensor (EOP sensor) downstream of the rocker arm oil control solenoid. If there is a difference between the oil pressure condition in the hydraulic circuit determined by the PCM command and the oil pressure condition determined by the status of the rocker arm oil pressure sensor (EOP sensor), 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 is ON, the rocker arm oil pressure sensor (EOP sensor) output remains high (49 kPa (14.5 inHg, 368 mmHg) or more).

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. Hold the engine speed between 1,100 rpm and 3,300 rpm for at least 16 seconds.

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

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.