What are the causes and symptoms of P2646 Code? | How to fix the P2646 Code?

P2646 code is not a very common code since most vehicles do not have actuators for the rocker arms of the engines they manufacture. The vehicles that have variable rockers that use this code are known to get this code when the engine gets sludge up from lack of oil changes at the proper interval or if the oil is too thick of a viscosity. This article explains the P2646 code symptoms, causes, and how to fix it.

What Does the P2646 Code Mean?

A P2646 code is an OBD code for the engine control module (ECM) detecting that the “A” rocker arm actuator control circuit for bank 1 has a performance issue or is stuck in the off position.

P2646 code

Some vehicles, like Hondas, have a variable valve timing and lift electronic control system, often referred to as VTEC, that increases fuel efficiency and engine performance. The VTEC system controls the rocker arm control system through the PCM.

In vehicles equipped with VTEC systems, the rocker arm control solenoid supplies hydraulic pressure to the variable timing and lift mechanism. This allows the VTEC system to adjust valve timing and lift as needed, and the ECM uses the rocker arm oil pressure switch to monitor and verify the oil pressure. This ensures that the variable timing mechanism can be properly activated.

If the ECM doesn’t receive the proper voltage signal from the rocker arm oil pressure switch, it will set the P2646 code. Furthermore, the “A” in this code refers to the intake camshaft, vehicle the bank 1 refers to the side of the engine that houses the number one cylinder.

Symptoms of the P2646 Code

  • Illuminated check engine light
  • A reduction in engine performance
  • The valve train may be excessively noisy if one or more rockers are stuck in the incorrect position.
  • Poor fuel economy  
  • Choppy acceleration
  • The engine valve train is moving as designed, which caused a low power condition.

Causes of the P2646 Code

Following are the most common causes of P2646 code:

  • The ECM detects a problem in the rocker arm system for bank 1
  • Clogged oil passages
  • Insufficient oil pressure
  • Dirty or low engine oil
  • The rocker arm actuator is clogged with sludge or is sticking intermittently.
  • The engine may have excessive sludge binding the rockers from moving, or the oil is too thick.
  • An issue with the PCM
  • Insufficient oil viscosity. Too thick of oil will cause the system not to work as designed.
  • Faulty rocker arm (VTEC) oil control solenoid
  • Damaged wirings

Read More: Symptoms and Causes of bad Rocker Arm

How to diagnose and repair the P2646 code?

Your mechanic will diagnose the P2646 code by doing the following:

  • Mount the OBD-II scanner into the OBD-II port, record all stored codes, and freeze frame data. Having freeze frame data is important as it can tell you in what condition the vehicle was in when the P2646 code turned up.
  • Start the inspection of the vehicle by checking the oil level and pressure. To properly function, the VTEC system needs adequate oil level and pressure, but if there is insufficient oil in the system, there cannot be enough pressure.
  • Check oil viscosity.
  • Check if there is any oil sludge. Irregular oil changes can lead to residue and sludge, which in turn can clog oil passages and cause the VTEC system to stop operating. One of the ways to fix this is to perform an engine oil flush and switch to synthetic oil, as this can clean out the residue.
  • Inspect all electrical connection and sensors and their integrity
  • Check all wired connection
  • Inspect the ‘A’ rocker arm actuator system
  • Perform the manufacturer pinpoint test on the rocker arm actuator system.

Common P2646 Code Diagnostic Mistakes

  • Replacing the actuator without verifying the actuator is the cause of the problem.
  • After repairing the vehicle, the engine control module (ECM) codes history is not removed from ECM software.
  • Failing to identify that incorrect oil viscosity is being used causes the code.

Read More: Symptoms and Causes of P2096 Code

What repairs can fix the P2646 code?

  1. Replacing the ‘A’ rocker arm actuator
  2. Repairing the wiring harness.
  3. Repairing the electrical connectors
  4. Flushing the oil passages of sludge
  5. Changing the oil and filter to the correct viscosity oil
  6. Changing the oil and filter to improve oil viscosity

How serious is the P2646 code?

Code P2646 is a code for the ‘A’ rocker arm control circuit performance problem. When the system is not working correctly, the rocker arms are not moving to a different position, causing a low-power situation.

FAQ Section

Can I drive with a P2646 code?

P2646 code doesn’t pose any serious danger to the driver since it causes a low-power situation. It is a serious code that should be fixed as soon as possible. Driving for prolonged periods is not recommended by qualified technicians with the P2646 code.

Any code that lights up your Check Engine Light should be dealt with as quickly as possible, so the P0646 code is no exception.

What is a rocker arm actuator system?

The rocker arm actuator is an oil pressure switch that controls the flow of oil to critical upper engine cylinder head components.

What does a rocker arm oil pressure switch do?

The Rocker arm oil pressure switch is used to verify the oil pressure in the Variable Valve Timing mechanism.

What is the function of the VTEC solenoid?

The main function of the VTEC solenoid is to control the flow of oil to the internal galleries of the overhead camshaft. Honda’s VTEC solenoid works alongside the oil pressure switch, together activating the camshaft’s high-performance setting.

What is an oil pressure sensor?

The primary function of your oil pressure sensor is to monitor your engine’s oil pressure and transmit this information to the cluster gauge on the instrument panel. Most modern cars come with an electronic control module to which the oil pressure directly communicates.

How difficult is it to inspect a P2646 Code?

Inspecting the P2646 code issue takes several steps and should be left to qualified technicians with previous experience working on these issues. Attempting to DIY this yourself can further damage your engine and its internals.

A technician will usually replace the “A” rocker arm actuator and repair the wiring harness or connectors leading to the actuator to inspect and repair the problem. They may also change the oil and filter to correct the oil viscosity and flush the engine passages of sludge if needed.

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