P2646: ‘A’ Rocker Arm Actuator System Performance (Bank 1)

What is P2646?

P2646 is a diagnostic trouble code (DTC) defined as “‘A’ Rocker Arm Actuator System Performance / Stuck Off Bank 1.”

Note: The ‘A’ in the P2646 code refers to the intake camshaft, and Bank 1 indicates the engine side with the #1 cylinder.

DTC P2646 is a generic OBD-II powertrain code. It’s set by your Powertrain Control Module (PCM) or Engine Control Module (ECM) when it detects the ‘A’ rocker arm actuator control circuit for Bank 1 has a performance problem or is stuck off.

Some vehicles, such as the Honda Accord, Honda Element, or Acura TL, come with Variable Valve Timing and a Lift Electronic Control (VTEC) System that helps increase fuel efficiency and performance. 

In vehicles with a VTEC system, the rocker arm control solenoid is responsible for supplying hydraulic pressure to the variable valve timing and lift electronic control mechanism. The VTEC system controls the rocker arm control solenoid (VTEC solenoid) via the PCM.

The PCM uses the rocker arm oil pressure switch (VTEC oil pressure switch) to monitor and verify this oil pressure, so the valve timing is activated correctly. If the PCM doesn’t receive the required voltage signal from the oil pressure switch circuit, it triggers code P2646.

Note: Some car manufacturers have this code specific to their models, like P2646 Honda for Honda Motor Company vehicles. 

Common symptoms

Here are some of the common P2646 code symptoms you can detect:

• An illuminated Check Engine Light 
• Increased fuel consumption
• Decreased engine performance 
• Excessively noisy valve train (if one or more rockers is stuck off in the wrong position)

Can I still drive?

The P2646 DTC code doesn’t cause any immediate threat to the driver. However, this trouble code indicates that the rocker arm actuator system isn’t functioning as required.

When the actuator system fails, it’ll prevent the rocker arm from moving to different positions, leading to poor engine performance. The fuel consumption of your vehicle could also increase.

In that case, you should see a mechanic as soon as possible to avoid any internal engine damage.

P2646 causes

Like any other OBD-II diagnostic trouble code, the P2646 code also has several potential causes.

Here are some of the likely reasons that could trigger this engine code and turn on the Engine Light:

Oil-related causes:

• Dirty engine oil
• Clogged oil passage
• Low oil level (especially if the oil change was not done correctly)
• Low oil pressure 
• Using the wrong oil viscosity or oil weight

Other causes:

• Rocker arm oil pressure switch (rocker arm actuator) failure
• Excessive engine sludge, preventing the rocker arm from moving 
• Faulty rocker arm oil control solenoid (VTEC solenoid) that fails to supply hydraulic pressure
• Faulty VTEC oil pressure sensor
• Open or short rocker arm oil pressure switch circuit
• Poor electrical connection in VTEC oil pressure switch
• A malfunctioning Powertrain Control Module or Engine Control Module

Diagnosis

P2646 is not a code to be ignored. You should get this check engine code diagnosed thoroughly and professionally.

Here’s how a certified technician will diagnose code P2646:

1. First, use an OBD-II scan tool to verify if it’s the P2646 code and record the freeze frame data for further diagnosis. Clear the code and see if the engine light comes on again.
2. Check if your vehicle is maintaining the required engine oil level and pressure. A low oil level will lead to low oil pressure.
3. If there’s no issue with the oil pressure or oil level, check if you’re using the correct oil viscosity (oil weight). Using thin oil can prevent the VTEC system from functioning properly. This usually happens if an oil change is not performed correctly.
4. Next, check for oil sludge that can also result from an irregular oil change. This can lead to a build-up in the oil passage and prevent the variable valve timing (VTEC system) from functioning.
5. Check all wired connections and look for broken, bent, or corroded pins or damaged wiring harnesses. Also, check for an open or short circuit.
6. Lastly, perform the manufacturer pinpoint test on the rocker arm actuator system to see if the system is at fault. 

Possible repairs for P2646 & Costs

P2646 is not a common check engine code since most vehicles don’t come with a rocker arm actuator. Vehicle manufacturers like Honda Motor Company and Acura may register their corresponding codes — P2646 Honda and Acura TL P2646.

The P2646 Honda or P2646 engine code usually appears along with an illuminated engine light when the engine gets sludged up, or if the oil is too thick and doesn’t flow properly via a small oil passage. Usually, an oil change using the correct oil viscosity will resolve this code.

If not, here are some other repairs a mechanic may suggest for the Honda Accord or other vehicles registering DTC P2646:

• Changing your vehicle’s engine oil and the oil filter
• Flushing the engine passages to remove sludge
• Replacing the ‘A’ rocker arm actuator
• Repairing the wiring or connector to the actuator

Repair Costs

The cost to resolve code P2646 involves an hour of diagnostic time that could fall between $75 and $150. This cost can vary depending on your location and the make and model of your vehicle.

Here are the average estimates (parts and labor) for some of the possible repairs:

• Changing engine oil and oil filter: $50 to $200
• Performing an engine oil flush: $100 to $150