Do the VTEC TEST in the INSPECTION MENU with the HDS.
Is the result OK?
YES
Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the rocker arm oil pressure switch and the PCM. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot.?
NO
The failure is duplicated. Go to step 3.
3.
Determine possible failure area (VTM line, others):
Determine possible failure area (VTM line, others)
?1.
Turn the vehicle to the OFF (LOCK) mode.
?2.
Disconnect the following connector.
Rocker arm oil pressure switch 2P connector
?3.
Turn the vehicle to the ON mode.
?4.
Check the parameter(s) below with the HDS.
Signal
Threshold
Current conditions
Values
Unit
Values
Unit
VTEC PRES SW
ON
Do the current condition(s) match the threshold ?
YES
Go to step 5.
NO
Go to step 4.
4.
VTEC system oil pressure check:
VTEC system oil pressure check
?1.
Turn the vehicle to the OFF (LOCK) mode.
?2.
Remove the rocker arm oil pressure switch (A), and attach the special tools as shown, then attach the rocker arm oil pressure switch to the oil pressure gauge adapter (B).
?3.
Reconnect the following connector.
Rocker arm oil pressure switch 2P connector
?4.
Start the engine.
?5.
Do the VTEC TEST in the INSPECTION MENU with the HDS.
?6.
Check the oil pressure.
Does the oil pressure increase to 392 kPa (4.00 kgf/cm2, 56.9 psi)?
Repair a short in the VTM wire between the PCM (B21) and the rocker arm oil pressure switch.?
NO
The VTM wire is OK. Update the PCM if it does not have the latest software, or substitute a known-good PCM, then recheck. If DTC P2646 goes away and the PCM was updated, troubleshooting is complete. If DTC P2646 goes away and the PCM was substituted, replace the original PCM.?