|Code||Fault Location||Probable Cause|
|P2649|| Rocker arm actuator A, bank 1 - circuit high |
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|Wiring short to positive, rocker arm actuator|
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What Does Code P2649 Mean?
OBD II fault code P2649 is a generic trouble code that is defined as “A” Rocker Arm Actuator Control Circuit High Bank 1”, and is set when the PCM (Powertrain Control Module) detects an abnormally high voltage or current in the control circuit(s) of the actuator that controls the variable valve timing on the camshaft labeled “A”. Note that camshaft “A” typically refers to the intake camshaft, while “Bank 1” always refers to the bank of cylinders on V-type engines that contains cylinder #1.
NOTE: Although code P2649 is generic trouble code, it largely only applies to the VTEC (Variable Timing and Electronic Control) systems on Honda vehicles whose VVT (Variable Valve Timing) systems work by engaging/disengaging rocker arms to activate or deactivate some engine valves to improve the volumetric efficiency of the engine under some operating conditions.
Unlike conventional VVT systems that use actuators to rotate camshafts relative to a fixed reference point, VTEC systems on Honda vehicles use pressurized engine oil to link a normally inactive rocker arm on the intake camshaft to an active rocker arm with a moveable locking pin. This action has the effect of bringing an additional intake valve into operation, which improves the mixing of the air/fuel mixture, which in turn, improves the combustion of the mixture.
In a fully functional VTEC system, the PCM uses data from engine and driveability sensors that include the Throttle Position Sensor, Throttle Pedal Position Sensor, Mass Airflow Sensor, and others to determine suitable conditions for VTEC activation, which typically occurs at engine speeds above a predetermined RPM value. When operating conditions are deemed suitable, the PCM will command an oil control solenoid to open, which allows pressurized engine oil to act on a locking pin that locks the inactive control arm to an active rocker arm, which, as stated earlier, brings an additional intake valve into operation on each cylinder.
When the system is deactivated, the PCM reverses the position of the oil control solenoid to relieve the oil pressure on the locking pin to allow spring tension to retract the locking pin. With the locking pin retracted, the valve train reverts to normal operation on all cylinders, i.e., all cylinders once again operate with only one active intake valve.
If however, the PCM detects an abnormally high voltage or current in the circuit(s) that control the oil control solenoid, it will interpret the condition as a short circuit or abnormally high electrical resistance in the circuit. When this happens, it will recognize that it cannot control the VTEC system effectively, and it will set code P2649 and illuminate the MIL (CHECK ENGINE) light as a result. Note that in some cases, and depending on both the application and the exact nature of the problem, the PCM may also initiate a fail-safe or limp mode to protect the engine against mechanical damage.
Where is the P2649 sensor located?
This image shows the location and appearance of the VTEC oil control solenoid on a Honda Civic application. Note though that the actual location and appearance of VTEC oil control solenoids vary between different Honda applications, so refer to reliable service information to locate and identify the VTEC oil control solenoid on the affected application correctly.
What are the common causes of code P2649?
Typical causes of code P2649 could include one or more of the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors in the VTEC oil control solenoid’s control circuit(s) (Most common)
- Defective or malfunctioning VTEC oil control solenoid
- Dirty, degraded, contaminated, and/or unsuitable oil causing the solenoid shuttle to stick
- Mechanical failure of the rocker arm locking mechanism (Rare, but not unheard of)
- Failed or failing PCM, but note that this is a rare event and the fault must, therefore, be sought elsewhere before any control module is replaced or reprogrammed
What are the symptoms of code P2649?
Typical symptoms of code P2649 are much the same across all applications, and could include one or more of the following-
- Stored trouble code and illuminated MIL (CHECK ENGINE) light
- Multiple other codes relating to misfires may be present along with P2649
- Depending on the application and the nature of the problem, varying degrees of power loss may be present
- Engine may run roughly at certain engine speeds
- In some cases, the engine may not idle, or it may stall unexpectedly at low engine speeds
- Fuel consumption may increase noticeably
- In some cases, the engine may be in a fail-safe or limp mode that will persist until the fault is found and corrected
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