P2647 Rocker Arm Actuator System is Stuck Open

Yesterday the check engine light came on 03 Accord EX 4-cyl auto, the code is P2647. According to the dealership and O’Reilly print out it can be a number of things, so I am looking for some guidance. The car starts running rough after 2700 rpms, and then (if you keep pressing accelerator) dies. So I can drive it now as long as I do not accelerate too much. (That is great for the gas mileage, but does not help on the on-ramps)
I did replace engine oil and filter yesterday, but the engine light is still on with the same code. The car has 175K miles.
O’Reilly manual suggests replacing:
• VTEC Oil pressure switch
• VCT Solenoid
• Pressure switch
• Solenoid Valve Assembly
The Honda Dealership said it might be:
• VTC Oil Control in Valve Assembly
• Valve Timing Oil pressure in the switch assembly
Any help in figuring out the faulty part will be much appreciated!

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I think you’ve dobe well so far, but at this point it needs the honda shop. There are a few possible root causes here.

Your engine uses a valve system that essentially has two camshfts, one foor low RPM operation and one for high RPM operation. When the ECU detects that the engine is at higher RPMs, it activates a secondary rocker arm system that changes the engine’s valvetrain operation fromm the “slow speed cam” [my term] to the “high speed cam”. It does this by (via a solenoid) “flipping” a control valve that redirects some pressurized oil to a hydraulic channel that engages the high speed rocker arms. It’s using the oil as a hydraulic fluid.

What’s gone wrong is that either
the ECU is not sending the signal based on the engine speed
the solenoid is not switching the valve that redirects the oil
the oil is for some reason not activating the highspeed rockers
or perhaps everything would work fine but the oil pressure is blocked from the valve assembly, which would mean the valve is getting switched by the solenoid but there’s insufficient oil oressure to do anything.

Sorry, but there’s no magic pill, no single likely part. Someone knowledgable will have to do some in depth diagnosis.

This is from a Honda service tip dated 03/01/2005:

DTC P2647: VTEC Oil Pressure Switch Circuit High Voltage

SOURCE: Honda Service News

TITLE: Replace VTEC Oil Pressure Switch for DTC P2646, P2647

APPLIES TO: 03-05 Accord 4-cylinder03-05 Element
02-05 CR-V


Got a vehicle in your shop with either of these DTCs?- DTC P2646 (VTEC oil pressure switch circuit low voltage)

  • DTC P2647 (VTEC oil pressure switch circuit high voltage)
    Replacing the VTEC oil pressure switch usually fixes the problem. If it doesn’t, then press on with normal troubleshooting.

Took it to the shop, $150 later for VTEC oil pressure switch and everything is fine. Thank you everyone for your help!

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I have the same symptoms with my Honda CRV 2005. We replaced all those things and the problem still persist.
Code was P2646 (vtec pressure switch voltage faulty). May 28th 2020; The mechanic replaced the valve timing solenoids. Replaced Right outer Tie Rod. + Front alignment. (paid $593.19).
Literally the next day it was still struggling to accelerate. cant go above 3000 rpms. everything you mentioned.

The VTEC solenoid valve is a different part, try replacing the VTEC oil pressure switch.