DTC Advanced Diagnostics: P2646
DTC P2646:Rocker Arm Oil Pressure Switch Circuit Low Voltage

General Description

Logic Decision
Rocker Arm Oil Pressure Switch
’ON’
’OFF’
Rocker Arm Oil Control Solenoid Command 'ON'
Failure
Normal
Rocker Arm Oil Control Solenoid Command 'OFF'
Normal
Failure

The VTEC system activates the rocker arm oil control solenoid with a 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 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 switch, the system is considered faulty, and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle
Sequence
None
Duration
16 seconds or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Engine coolant temperature [ECT SENSOR 1]
86 °F (30 °C)
–
Engine speed [ENGINE SPEED]*, *1
1,150 rpm
–
Engine speed [ENGINE SPEED]*, *2
1,400 rpm
–
Vehicle speed [VEHICLE SPEED]
10 mph (15 km/h)
–
12 volt battery voltage [BATTERY]
10.5 V
–
Shift lever position*1
Other than P or N
*: Variable that is depending on the engine load.
*1: CVT model
*2: M/T model
[ ]: HDS Parameter

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

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 failure
Rocker arm oil control solenoid VTS line open
Rocker arm oil control solenoid VTS line short
Rocker arm oil pressure switch failure
Rocker arm oil pressure switch VTM line open
Rocker arm oil pressure switch VTM line short
Oil passage clogged

Confirmation Procedure
Operating Condition
1.
Start the engine. Hold the engine speed [ENGINE SPEED] at 3,000 rpm without load (CVT in P or N, M/T in neutral) until the radiator fan comes on.
2.
Drive the vehicle at an engine speed [ENGINE SPEED] 1,400 rpm or more for at least 16 seconds.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
With the HDS
Do the VTEC TEST in the INSPECTION MENU with the HDS.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

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 12 volt battery.