Diagnosing P2646 on 2005 Honda Odyssey Touring

Sent this to Mr. Danner but he said appropriate place to put it is here. Not sure, i'm new lol!

Hi Mr. Danner,
I have a 2005 Odyssey Touring that I have been trying to diagnose and fix with no luck. John Clark from Odyclub.com said you were the guy to contact since I live close to Pittsburgh. He said you He said for a fee you diagnose problems. If this is correct could I get more info on how I to get something set up? Lol he also said he wants you to do a video of it! I have been getting the P2646 rocker arm actuator code. I have cleaned the screen on the spool assembly, swapped out a used but working VTEC oil pressure switch and checked the solenoid. I tested the solenoid with a test light and shows the circuit is complete but I am not sure if it is mechanically functioning as I really didn't see any movement of the pin inside. Thanks, Mike

I've never worked on this system before, but I can tell you a quick way that I use when I'm not sure if the solenoid is working or not. Make sure Your getting power (+) on the white/green wire. Also make sure you are getting a ground on pin 1 (Black wire) If I'm reading the diagram correctly the ground on this car comes from the PCM to the VTEC solenoid then supplies the ground on coils 1, 2,and 3. If you have both power and ground at the VTEC, I have used a stethoscope to hear if it is firing. You probably hear better than I do, so I am guessing that you don't have both power and ground. The only thing confusing me is the positive on this car (white/green) wire also goes to the PCM. So I am not sure if it's a ground side switch or not. Reading the diagram I think it is a positive side switch. But that is something to get you started.

Hey, Thank you for that info on the wiring! I will check it out see what I find. I am guessing that wire is only getting power when in VTEC rpm/load range though. Do you know will revving the engine activate VTEC or does it have to be under load

VTEC will only engage under load. Am I correct in believing that green wire will then only get power under load/in VTEC range?

Have you checked the oil? How many miles since it was changed? Checked the oil pressure?

There is also a TSB for a PCM reflash when it sets this code

Mike355F1 wrote: VTEC will only engage under load. Am I correct in believing that green wire will then only get power under load/in VTEC range?

Yes. Here is a few test. Voltage + on green wire - on good ground KOER solenoid should be closed and you should get 0vdc. Driving the car under load , on the decal you should read battery voltage.
You can also do a résistance test on the solenoid. Unplugged the solenoid should read about 20 ohms. Hope that helps

I just removed the solenoid and applied 12volts. As you can see in the video link, You can hear it doing something and I can see slight movement (maybe 1/16 of an inch) of the pin inside. What I'm not sure of is if there should be more movement and should I see one of those two ports closing or both opening at the same time???? drive.google.com/file/d/0B2v...ew?usp=sharing

bruce.oliver wrote: Have you checked the oil? How many miles since it was changed? Checked the oil pressure?

But I agree with Bruce as well. Do the Resistance test on the solenoid is fine if the solenoid is suspect. But by all means make sure you have changed the oil and have oil pressure before you do the over the road test

Bruce, I did check with Honda and I have the latest flash or so so they say. Also, I did change the oil and made sure it was the recommended 5w20. Thanks

Dave, Did you see the video I posted right before your previous post? Any thoughts? And yes, I do have oil pressure thank goodness!

Mike355F1 wrote: Dave, Did you see the video I posted right before your previous post? Any thoughts? And yes, I do have oil pressure thank goodness!

I clicked on the link but Google said the file doesn't exist? :blink: I would to the Ohm test on the solenoid first. If you get 20 ohms or so I would go to the next step. If all the voltages are good, Then I would look at the mechanical aspects of the solenoid. It's possible the solenoid is mechanically faulty, but didn't you already change it out for a known good? Also make sure the connections are good on both the solenoid and the PCM. Make sure you not only are checking the signal wire, but make sure it is getting a good ground. That is commonly overlooked and can make you pull your hair out!!!:woohoo:

Try this link
I replaced the VTEC oil pressure switch. I am now trying to determine if the VTEC solenoid/control valve is functioning. I do not have a scan tool so I have no way of performing those tests you mentioned. I am realizing this forum is more for professionals and not backyard mechanics lol! I do not think it is functioning properly mechanically but I do not know for certain as I can't find anything else to compare it to online.

On the 2005 Odyssey you have the 1st generation VCM (variable cylinder management) which controls cylinder pause on the intake/exhaust valve side. It is done so on only the rear cyl head- Bank 1. (2nd gen VMC controls both heads-intake/exhaust valve sides). This system runs on 3 or 6 cylinders. The Spool valve assembly in charge of actuating 3 Cylinder Pause mode consists of mainly three components; VTEC spool valve, EOP (engine oil pressure sensor), and VTEC solenoid valve. There is a PCM software update for a P2647 VTEC system stuck OFF which does not apply to you.

Under NORMAL conditions
*VTEC solenoid command ON to actuate 3 cylinder pause mode the PCM is expecting EOP sensor to drop LOW (from experience under 6-8 psi is criteria for LOW)
*VTEC solenoid command OFF- engine is running conventional 6 cylinder operation, the PCM is expecting the EOP sensor to stay HIGH (above 6psi).

For technicians with higher end scanners there is a VCM TEST available which commands the VTEC solenoid ON and OFF while monitor oil pressure changes, most of the time it is intermittent so you have to dig deeper)

I would like to add that on a standard VTEC system WITHOUT VCM, the logic decision is opposite. With VTEC solenoid command ON, PCM expects HIGH oil pressure from VTEC pressure switch and vice versa.

Your next step is to do the same thing you were doing in your video, but this time use an air blow nozzle and blow through all the 3 ports while energizing / deenergizing the solenoid. I would also clean the ports with brake cleaner.
With the solenoid OFF, you should not have any air leaking through the bottom center pintle. A VTEC solenoid valve in good working condition has an air tight seal and should not leak. The air nozzle will also help clean up gunk and build up which may be causing the pintle to stick.
Post of a video of it for others to see, if you can.

CurrentDraw, Thanks for that thorough explanation of how the system works and how the solenoid operates at each step. I cleaned it thoroughly as you said and no air leaks through the pintle without power. When power is supplied power flows as it should. Unfortunately because of a lack of extra hands I was unable to video with my phone. After cleaning I reinstalled drove it but still the same problem.

Dave101, I borrowed a multimeter and set it to the 200 Ohm scale. When I touch the leads it goes to 1 on the far left of the screen. What does this mean? Does this mean it is electronically bad since it isn't around 20? I had assumed when I provided it with power and it operated that meant it was electronically ok. Again I apologize for my ignorance and thank you guys for your patience with me! Thanks

Most meters I've used (Fluke, Snap-on, etc.) will say OL but I'm pretty sure "1" on the ohm meter means the resistance is higher than the ohm setting on the meter. Try a higher ohm setting or an auto-ranging scale.

I may have been using it incorrectly the first time or the meter is a piece of junk but here is a video of what I am seeing now. I thought when the leads were touched it should go to 0 but mine goes to 4.9 and when I touch the solenoid terminals it goes to 5.9

That meter isn't too trustworthy. The usual resistance on a set of leads is usually around 0.1-0.3 ohms. Some meters have a way of setting that to zero but showing 4.9 ohms on a set of leads means the leads are bad or the meter is bad. What happens if you put a jumper wire directly across the jacks on the meter? See if you can rule out a problem with the meter or the leads.

If the zero ohm point is 4.9 ohms and you touch it on that solenoid and it goes from 4.9 to 5.9 ohms, assuming the meter is accurate, that means that the resistance of the solenoid is 1 ohm which is WAY too low and would cause high current about 12-14 amps to go through that circuit when the solenoid is activated. The coil is essentially shorted if that meter reading is correct. If it's actually shorted it could have damaged the PCM driver for the solenoid.

So, you need trustworthy test equipment first. It might be accurate, we don't know, but that meter isn't trustworthy at this point.

When holding the leads together, wiggle the the lead where it connects to the meter and see if that 5 ohm value changes

Ok I borrowed a good Fluke multimeter from a buddy and the sensor is reading 15.9 ohms. That other meter is all over the place....tested several different times over a few hours and got way different readings each time.