Advanced Diagnostics

Advanced Diagnostics - DTC P2648: Rocker Arm Oil Control Solenoid Circuit Low Voltage (Engine Type: R18Z1, R18A9)

General Description






The VTEC system activates the rocker arm oil control solenoid by a command from the engine control module (ECM)/ powertrain control module (PCM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that switches valve timing between low and high. If the return signal is OFF (low) when the ECM/PCM outputs the ON (high) signal to the rocker arm oil control solenoid, the ECM/PCM detects a malfunction and stores a DTC.

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






Enable Conditions






Malfunction Threshold
The return signal is OFF (low) for at least 2.0 seconds when the ECM/PCM outputs the ON (high) signal to the rocker arm oil control solenoid.

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

- Rocker arm oil control solenoid VT_SOL line short to ground
- Rocker arm oil control solenoid failure
- ECM/PCM internal circuit failure

Confirmation Procedure (Engine Type: R18Z1)

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

With the Driving Pattern
1. Start the engine. Hold the engine speed [ENGINE SPEED] at 3,000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on.
2. Drive immediately at a steady engine speed [ENGINE SPEED] at 2,800 rpm or more for at least 2 seconds.

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

Confirmation Procedure (Engine Type: R18A9)

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

With the Driving Pattern
1. Start the engine. Hold the engine speed [ENGINE SPEED] at 3,000 rpm without load (in P or N) until the radiator fan comes on.
2. Drive the vehicle at a steady speed of 9 mph (14 km/h) or more and engine speed [ENGINE SPEED] between 1,100 - 3,500 rpm for at least 2 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 ECM/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.