DTC Troubleshooting

DTC Troubleshooting: P2646

DTC P2646: Rocker Arm Oil Pressure Switch Circuit Low Voltage

Special Tools Required

- Pressure gauge adapter 07NAJ-P07010A
- A/T low pressure gauge w/panel 07406-0070301
- A/T pressure hose 07406-0020201
- A/T pressure hose, 2,210 mm 07MAJ-PY4011A
- A/T pressure adapter 07MAJ-PY40120
- Oil pressure hose 07ZAJ-S5AA200

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information. Initial Inspection and Diagnostic Overview

1. Check the engine oil level.

Is the level OK?
YES - Go to step 2.

NO - Adjust the engine oil to the proper level, then go to step 21.


2. Turn the ignition switch to ON (II).

3. Clear the DTC with the HDS.

4. 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, the rocker arm oil control solenoid, and the ECM.

NO - Go to step 5.


5. Turn the ignition switch to LOCK (0).

6. Disconnect the rocker arm oil pressure switch 2P connector.

7. Turn the ignition switch to ON (II).

8. Check the VTEC PRES SW in the DATA LIST with the HDS.

Is SWITCH ON indicated?
YES - Go to step 16.

NO - Go to step 9.


9. Turn the ignition switch to LOCK (0).

10. Remove the cowl cover and the under-cowl panel. Service and Repair

11. 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 attachment (B).
NOTE: Install the parts in the reverse order of removal with a new O-ring.

12. Reconnect the rocker arm oil pressure switch 2P connector.

13. Start the engine.

14. Do the VTEC TEST in the INSPECTION MENU with the HDS.

15. Check the oil pressure.

Does the oil pressure increase to at least 392 kPa(4.0 kgf/cm2, 56.9 psi)?
YES - Replace the rocker arm oil pressure switch, Service and Repair then go to step 20.

NO - Inspect the following items. If they are OK, replace the rocker arm oil control valve, Service and Repair then go to step 20.

- VTEC system's oil line

- Operation of the rocker arm VTEC Rocker Arm Test







16. Turn the ignition switch to LOCK (0).

17. Jump the SCS line with the HDS.

18. Disconnect ECM connector C (44P).

19. Check for continuity between ECM connector terminal C22 and body ground.

Is there continuity?
YES - Repair short in the wire between the ECM (C22) and the rocker arm oil pressure switch, then go to step 20.

NO - Go to step 27.






20. Reconnect all connectors.

21. Turn the ignition switch to ON (II).

22. Reset the ECM with the HDS.

23. Do the ECM idle learn procedure. ECM Idle Learn Procedure

24. Do the VTEC TEST in the INSPECTION MENU with the HDS.

25. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P2646 indicated?
YES - Check for poor connections or loose terminals at the rocker arm oil pressure switch, the rocker arm oil control solenoid and the ECM, then go step 1.

NO - Go to step 26.


26. Monitor the OBD STATUS for DTC P2646 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 25, go to the indicated DTC's troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the rocker arm oil pressure switch, the rocker arm oil control solenoid, and the ECM, then go to step 1. If the screen indicates NOT COMPLETED, go to step 24.


27. Reconnect all connectors.

28. Update the ECM if it does not have the latest software, ECM Update or substitute a known-good ECM. Initial Inspection and Diagnostic Overview

29. Do the VTEC TEST in the INSPECTION MENU with the HDS.

30. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P2646 indicated?
YES - Check for poor connections or loose terminals at the rocker arm oil pressure switch, the rocker arm oil control valve, and the ECM. If the ECM was updated, substitute a known-good ECM, Initial Inspection and Diagnostic Overview then go to step 29. If the ECM was substituted, go to step 1.

NO - Go to step 31.


31. Monitor the OBD STATUS for DTC P2646 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?
YES - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM. Service and Repair If any other Temporary DTCs or DTCs were indicated in step 30, go to the indicated DTC's troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the rocker arm oil pressure switch, the rocker arm oil control valve, and the ECM. If the ECM was updated, substitute a known-good ECM, Initial Inspection and Diagnostic Overview then go to step 29. If the ECM was substituted, go to step 1. If the screen indicates NOT COMPLETED, go to step 29.