Persistent P2647 2013 Acura TL SH AWD 3.7 L V6

[Hallowed_point]

I've owned my 2013 Acura TL SH AWD 3.7 L 6 speed manual for just over 3 years now. I love this car and intend on keeping it until it goes boom. Bought with 200,000 (mainly highway) kms and just hit 250,000 recently.

I've had a persistent P2647 "Rocker Arm Oil Pressure Switch (A) Circuit High Voltage/VTEC system stuck on code which comes only on a cold start and only when the vehicle is parked outside in the winter or late fall months. The car is parked outside 365 and is not plugged in as there are no nearby outlets. Run 0w20 synthetic oil and OEM filter changed regularly at Silverhill Acura. Oil is always changed at 15% life. Burns a little bit, about 1 litre in ~6000 kms when I'm really driving it hard (shifting at 6800 rpm often once warm) over the summer. It's a J Series, meant to do that.

Symptoms are: cold start stumble where the engine revs to about 2500 rpm erratically for about 5 seconds and then settles down. I've had the VTEC solonoid replaced with an OEM unit, have never seen a "check oil or low oil pressure" light since I've owned it. And VTEC always works regardless of the code. The annoyance is when the check engine light pops up, it turns off the SH-AWD and it becomes a 305 horsepower FWD sedan. I keep a code reader in my car to clear it, which works however it stores a permanent code which takes several days/weeks to "actually" clear out of the PCM.

This code seems to be common with J Series vehicles, Odysseys , Ridgelines, Accords & 3rd/4th gen J series TL's. Before I contemplate throwing any more money at a seemingly harmless but annoying problem, do we have any Honda/Acura techs here who have some new ideas?

[Flexray]

P2647 sets when the VTEC oil pressure sensor sees pressure when the VTEC solenoid is not activated. This is how I would diagnose this problem.

I would let the vehicle sit over night so it is stone cold. With a scan tool, I would pull up the VTEC solenoid activation and the pressure sensor data before starting the engine. Once I'm ready, start the engine and command the solenoid on and off rapidly while watching the pressure sensor, every time the solenoid is activated the sensor should see pressure. If the solenoid is command on and no pressure is seen or commanded off and pressure is still seen the solenoid is jamming. The spool valve on the solenoid is a very close tolerance valve, as the engine warms up the tolerances expand making it less prone to jamming. If you do not have a scan tool, you can jump power to the solenoid and monitor the pressure sensor with a volt meter, but the engine module powers the solenoid by pulse width modulation, jumping direct power to it won't fully replicate how the valve normally works.

If the solenoid jambs, remove it off the engine and inspect the oil inlet screen. If it is broken the bits of screen will go through the solenoid and rocker arm plungers and basically damage everything. The spool valve should not have any marks or scoring on it. If something is eating it's self inside the engine, the debris and metal will jamb solenoids.

If the blue/black wire on the pressure sensor has a short to ground, the engine module will think the VTEC system has pressure in it. Back probe the blue and black wire and test for ohm's to ground while wiggling the whole engine wiring harness bit by bit, you should have no ohms to ground at anytime on that wire.
Hope this helps.

[Hallowed_point]

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P2647 sets when the VTEC oil pressure sensor sees pressure when the VTEC solenoid is not activated. This is how I would diagnose this problem.

I would let the vehicle sit over night so it is stone cold. With a scan tool, I would pull up the VTEC solenoid activation and the pressure sensor data before starting the engine. Once I'm ready, start the engine and command the solenoid on and off rapidly while watching the pressure sensor, every time the solenoid is activated the sensor should see pressure. If the solenoid is command on and no pressure is seen or commanded off and pressure is still seen the solenoid is jamming. The spool valve on the solenoid is a very close tolerance valve, as the engine warms up the tolerances expand making it less prone to jamming. If you do not have a scan tool, you can jump power to the solenoid and monitor the pressure sensor with a volt meter, but the engine module powers the solenoid by pulse width modulation, jumping direct power to it won't fully replicate how the valve normally works.

If the solenoid jambs, remove it off the engine and inspect the oil inlet screen. If it is broken the bits of screen will go through the solenoid and rocker arm plungers and basically damage everything. The spool valve should not have any marks or scoring on it. If something is eating it's self inside the engine, the debris and metal will jamb solenoids.

If the blue/black wire on the pressure sensor has a short to ground, the engine module will think the VTEC system has pressure in it. Back probe the blue and black wire and test for ohm's to ground while wiggling the whole engine wiring harness bit by bit, you should have no ohms to ground at anytime on that wire.
Hope this helps.

Wow, thank you so much! That gives me some fresh ideas to trouble shoot this code.