Generic P2647 wording describes a high rocker-arm switch state, but Odyssey J35 diagnostics normally organize VCM pressure faults by bank, often with P3400/P3497. Verify raw code, module and VIN before repair. Bulletin 13-021 does not include Odyssey. If Honda data confirms an applicable high-state fault, graph VCM command against feedback, load-test the circuit and determine whether oil pressure fails to release. An open signal circuit and trapped hydraulic pressure can appear identical at the PCM.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Confirm Honda raw code and module.
What can set P2647—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Wrong scan definition/profile | Honda-capable tool differs | VIN/module/raw-code check |
| Open/high-resistance circuit | High state persists under loaded test | Terminal/voltage-drop test |
| VCM valve fails to release | Command off, pressure state active | Bank actuation/pressure test |
| Oil passage/condition problem | Delayed hydraulic response | Oil/passage inspection |
| Verified switch fault | Circuit and hydraulics pass | Exact switch test |
High state has two meanings
An open wire can read high; retained pressure can keep a healthy switch high.
Command, voltage and pressure testing separate them.
Vehicle identification is diagnostic
Wrong module/profile data can point to another Honda engine family.
Record VIN, PCM identity and full DTC before ordering parts.
J35 VCM is not K24 VTEC
Both use oil-controlled rocker hardware, but bank layout and fault logic differ.
Use Odyssey service information.
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Raw code/module/status
- P3400/P3497 companions
- VCM command/bank state
- Oil level/grade/history
- ECT/load/voltage
- Scan profile/calibration
A practical diagnostic workflow
- 01Confirm raw information
Generic wording alone is insufficient.
- 02Use exact J35 schematic
Identify bank, valve and switch.
- 03Exclude 13-021
It does not list Odyssey.
- 04Graph command versus feedback
Separate constant and delayed high states.
- 05Test circuit and release pressure
Distinguish open wiring from trapped oil.
- 06Verify both transitions
Confirm no pending DTC.
Do not treat an Odyssey as a CR-V and do not replace a switch until the J35 code/circuit is verified. High state may be electrical or hydraulic.
Why the model year changes the test
Odyssey diagnostics span several J35 V6 generations, port and direct injection, VCM cylinder deactivation, conventional and newer EVAP hardware, plus six cylinder-specific misfire codes and two catalyst banks. Confirm VIN, model year, engine/calibration, emissions label and current Honda warranty/campaign status. Do not transfer four-cylinder Accord, Civic or CR-V VTEC bulletins to this J35-powered minivan.
- 13-021 does not cover Odyssey.
- P3400/P3497 are common J35 VCM pressure-code references.
- High state can indicate an open circuit or retained pressure.
- Exact VIN/calibration controls the definition.
P2647 FAQ
Does 13-021 apply?+
No.
Can a generic scanner mislead?+
Yes; verify Honda enhanced data.
How is high different from low?+
It changes likely circuit and hydraulic causes.
Can I drive?+
Limit load; stop for oil warning/noise.
Is a switch always bad?+
No; wiring and oil release can mimic it.
Why check P3400/P3497?+
They identify common bank-specific VCM faults.
Can dirty oil matter?+
Yes, by delaying hydraulic response.
What confirms repair?+
Correct bank feedback and no pending DTC.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Honda ServiceExpressHonda VIN-specific diagnostics, wiring, bulletins and campaign status↗02Honda Owners — Odyssey manualsOfficial model-year warnings, maintenance and operating information↗