|Code||Fault Location||Probable Cause|
|P2656|| Rocker arm actuator A, bank 2 - performance problem or actuator stuck off |
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|Rocker arm actuator|
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What Does Code P2656 Mean?
OBD II fault code P2656 is a generic trouble code that is defined as “A Rocker Arm Actuator System Performance/Stuck Off Bank 2”, and is set when the PCM (Powertrain Control Module) detects a fault, failure, or defect in electrical circuits of the VVT (Variable Valve Timing) oil control solenoid on Bank 2.
In the context of this code, “System performance” could mean that the PCM sees the oil control solenoid to be in a position it should not be in given the current operating conditions, while “Stuck off” means that the oil control solenoid is stuck in the “OFF” position, and cannot be switched to the “ON” position. Note that “Bank 2” refers to the bank of cylinders on V-type engines that does not contain cylinder #1.
Most car manufactures have adopted one of many possible strategies to alter the valve timing on their engines to increase engine power under some conditions without increasing fuel consumption at the same time. In practice though, altering the valve timing under some operating conditions has the effect of improving combustion under those conditions to reduce exhaust emissions.
As a practical matter, and even though there are significant differences in design specifics between various systems, all VVT systems use pressurized engine oil to act on one or more actuators to change the intake valve timing relative to a base setting. Thus, by opening intake valves earlier in the intake stroke, and keeping them open for longer means that the air/fuel mixture is not only more homogeneous, but the additional swirl produced by the altered valve timing improves the propagation of the combustion flame front throughout the mixture.
The practical effects of this include more power at lower engine speeds, improved fuel consumption at low engine speeds, and measurably reduced exhaust emissions at almost all engine speeds.
In terms of operating principles, the PCM collects data from various engine sensors to determine the most effective point at which to activate the VVT system. When this happens, the PCM opens an oil control solenoid to allow pressurized engine oil to act on the VVT actuator(s). Exactly how the actuators do this depends on the specific system, but in all cases, the actuator changes the moment the intake valves open relative to a base valve timing setting.
When the VVT system is deactivated above or below a certain engine speed, the PCM sends a signal to the oil control solenoid to reverse the position of the solenoid shuttle to allow the pressurized in the VVT actuator(s) to return to the general oil circulation system.
Note that in the deactivated state, oil can neither enter nor leave the VVT actuator, and in cases where the solenoid is stuck in the deactivated state as indicated by an integral position switch, and the PCM cannot open the solenoid, it will recognize that it cannot control the VVT system effectively, and will set code P2656 as a result.
Where is the P2656 sensor located?
This image shows a typical VVT oil control solenoid, with this particular example from a Toyota Lexus application. Note though that while there are slight differences in design specifics between oil control solenoids, the basic design and appearance of all VVT oil control solenoids follow this general pattern.
However, while all VVT oil control solenoids resemble each other, their actual locations on engines of different manufacturers vary greatly. Therefore, the location of VVT oil control solenoids on any affected application must be researched and verified to prevent the possible replacement of wrong parts and components.
What are the common causes of code P2656?
Note that while there are significant differences in the design specifics of VVT systems between manufacturers, engine models, and engine types, the most common causes of code P2656 are, for the most part, the much the same across all applications and designs. Typical causes could, therefore, include one or more of the following-
- Dirty, degraded, contaminated, or unsuitable oil
- Low oil levels
- Faulty or defective VVT actuator
- Faulty or defective VVT actuator position switch
- Damaged, burnt, corroded, or disconnected wiring and/or electrical connectors at almost any point in the VVT oil control solenoids control circuit(s)
- Mechanical failure of the affected VVT oil control solenoid
- Failed or failing PCM or another control module, but note that this is rare, and the fault must, therefore, be sought elsewhere before any control module is replaced
What are the symptoms of code P2656?
Most common symptoms of code P2656 are much the same across all applications and designs but note that the severity of one or more symptoms could vary between different applications and designs. Typical symptoms could include one or more f the following-
- Illuminated MIL (CHECK ENGINE) lamp
- One or more stored trouble codes, depending on the application and specific VVT system in use
- Idling sped may fluctuate, or the idling may be rough, erratic, or the engine may not idle at all
- Engine may stall at low engine speeds, although this is not common
- Reduced engine performance
- Varying degrees of power loss above or below certain engine speeds, depending on the application
- Reduced fuel economy
- Increased emissions
- Vehicle may fail a mandatory emissions test
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