DTC Advanced Diagnostics: P2651 (3.0L Engine)
DTC P2651: Rocker Arm Oil Pressure Stuck High Pressure
General Description
| Logic Decision | Rocker Arm Oil Pressure Sensor | |
|---|---|---|
| Low Oil Pressure(Oil pressure < Threshold) | High Oil Pressure(Oil pressure > Threshold) | |
| Rocker Arm Oil Control Solenoid Command 'ON' | Normal | Failure (P2651) |
| Rocker Arm Oil Control Solenoid Command 'OFF' | Failure (P2652) | Normal |
The variable cylinder management (VCM) 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 cylinder pause VTEC system mechanism that pauses the intake and exhaust valves on the rear banks. The PCM monitors oil pressure in the hydraulic circuit of the VTEC mechanism using the rocker arm oil pressure 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, the system is considered faulty, and a DTC is stored.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 4.0 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after cylinder pause | 2.0 seconds | - |
| Engine coolant temperature [ECT Sensor 1]* | 70 deg.F (158 deg.C) | - |
| Estimated TWC temperature* | 608 deg.F (320 deg.C) | 3, 596 deg.F (1, 980 deg.C) |
| Estimated exhaust gas temperature* | - | 70 deg.F (1, 832 deg.C) |
| Engine speed [Engine Speed]* | 900 rpm | 3, 300 rpm |
| Vehicle speed [Vehicle Speed]* | 0 mph (0 km/h) | - |
| Fuel feedback* | Closed-loop | |
| Other* | Other than accelerator pedal is released | |
| No abrupt deceleration | ||
| Other than fuel cut-off during deceleration | ||
| Other than during wide open throttle | ||
*: Conditions to cylinder pause[ ]: HDS Parameter
Malfunction Threshold
The rocker arm oil pressure sensor output remains high (more than 37 kPa (0.38 kgf/cm 2, 5.4 psi) when the rocker arm oil control solenoid is ON.
Possible Cause
- Rocker arm oil pressure sensor POILCS line open
- Oil passage clogged
- Rocker arm oil control solenoid stuck
Confirmation Procedure
Operating Condition
- 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, then let it idle for at least 4 seconds.
- Drive the vehicle on a flat road in 4th gear at a steady engine speed [Engine Speed] between 900 - 3, 300 rpm for at least 4 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 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, the freeze data, and the on-board snapshot 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, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.