Brand new owner of a 2010 base model TL. (120,000 miles). First time i went past 5000 rpms, car stumbled like
it hit a rev limiter, stopped accelerating, then blew a 2646 code which points to low voltage for
a rocker arm oil pressure switch. Dealership thinks, with a 90% probability, that it's the oil pump
though they didn't test it for pressure. Does this sound like it makes sense?

 

Did you take your car into the dealership for them to diagnose?

There's a possibility this code is appearing due to a low oil level. I would check that before taking it in.

 

vtec (above 5k RPM) operates on oil pressure.
it could be various different things, only way to tell is to troubleshoot...
it may be low oil, it may be the pump, it may be the rocker arm oil pressure switch

 

I did take it to the dealership and as a backyard mechanic, oil level was the first thing I checked and
it was fine. The original owner kept extensive records. Today's diagnosis didn't cost me anything
because the previous owner worked at the dealership. Looks like my next step is to get the oil pump
pressure checked which will cost me one hour of labor.

 

DTC P2646 - rocker arm oil pressure switch circuit low voltage.

The rocker arm oil pressure switch may fail intermittently.

The symptom may be intermittent and you may not be able to duplicate it after clearing the DTC.

Start with clearing the DTC and see if the DTC comes back under the same driving conditions. Repeat it a few times to see how intermittent the issue is.

 

Thanx for your input. It does come back everytime I run above 5000 rpms

 

Thanks for the update. We'll await your dealer diagnosis.

 

Not getting anywhere with recent diagnostics at the Acura dealership. Dealer was following a flow chart and installed a new valve assembly with a new
solenoid switch. Well, that didn't work and it cost me $565. Further diagnosis is needed and they probably new to pull the valve covers.
I would think that the technician would know if it could be an oil pump. (which is an expensive repair). Not sure how much I want to spend here since
the car only cost me $6500.

 

So my choices are to live with a car with about a 5500 RPM redline before the car craps out or spend potentially
thousands of dollars to fix a $6500 car.

 

Going through the exact same thing. Did you ever figure out what it was? I intermittingly have P2646 when going above 5k. Started happening after the dealer replaced rod bearings for recall.

 

I had the P2647 "high voltage" intermittently. I changed the spool valve assembly and problem went away. The cost of just the oil pressure switch for the VTEC was more than half the cost of the assembly so I bought the assembly which came with pressure switch and vtec solenoid. You'd have to stick your hand in behind the valve cover to disconnect the clip from its hook then unclip it.

 

Welp, I'm having the same issue with my 2008 rdx. did you end up solving it? I saw one reddit post where someone had even mentioned it being an issue with an ignition coil. This code seems pretty hard to track down.

 

I changed my own oil and filter with high quality parts. I'm still pushing the car to see if it will come back.

I bought Honda's Info tech for the day, here's all the have about the p2646 for the 2008 RDX:


Diagnostic Flowchart 1/4

Diagnostic Flowchart 2/4

Diagnostic Flowchart 3/4

Diagnostic Flowchart 4/4

 

thanks for the response, at this point I think I may just try to find the part for the whole solenoid assembly and replace that I think its 15810RWCA01 or VVT381. I'll update if it goes anywhere.