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AutoTech08, Workshop owner
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Experience:  Diploma in Automotive Engineering, 30 years working experience.
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my car is reading p2646 and p2647 which is vtec oil pressure

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my car is reading p2646 and p2647 which is vtec oil pressure switch circuit low voltage and high voltage. What would cause that? How do i fix?

Hi there,

 

What is the year, model and engine variant?

Customer: replied 8 years ago.
2005 Honda Civic SI - K20A3

Hi,

 

Possible causes are low engine oil pressure due to :

1. Insufficient engine oil level.

2. Weak oil pump or clogged oil lines.

 

You would need to check the engine oil level, test oil pressure and VTEC switch circuit and operations, wireharness and PCM. to verify which is the cause.

Customer: replied 8 years ago.
woulndt i get an oil light if it was oil pressure or something

Hi ,

 

Yes, if oil pressure is low, the indicator lamp should show, however if the switch is inaccurate, it might not show.

 

If the oil passage to the VTEC valves are clogged, oil pressure would not show anything.

Customer: replied 8 years ago.
The effect it is having on the car is that while driving once i reach 4 grand the car sort of shuts down. I can no longer accelerate almost as if I reached the rev limiter or governor. It happens in every gear but is not consistent. When I start the car it happens in every gear or not at all. I changed the VTEC oil pressure switch and reset the ECU but it didnt solve the problem. Does this seem to coinside with what you think I should check?

Hi there,

 

The symptoms shows the VTEC valve is not operating and providing the fault code. Since the valve has been replaced, the next thing to check would be the oil pressurre at the valve and PCM.

 

DTC P2646: VTEC OIL PRESSURE SWITCH CIRCUIT LOW VOLTAGE

Special Tools Required.

 

Pressure gauge adapter 07NAJ-P07010A
A/T low pressure gauge w/panel 07406-0070300
A/T pressure hose 07406-0020201
A/T pressure hose, 2,210 mm 07MAJ-PY4011A
A/T pressure adaptor 07MAJ-PY40120
Oil pressure hose 07ZAJ-S5A0200

 

1. Turn the ignition switch OFF.

 

2. Check the engine oil level.

Is the level OK?

YES: Go to step 3.

NO: Adjust the engine oil to the proper level.

 

3. Turn the ignition switch ON (II).

4. Reset the ECM

5. Start the engine. Hold the engine speed at 3,000 RPM with no load (in neutral) until the radiator fan comes on, then let it idle.

6. Test-drive under following conditions: Accelerate in 1st gear to an engine over 5,000 RPM. Hold the speed for at least 2 seconds.

Is DTC P2646 indicated?

YES: Go to step 7.

NO: Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the VTEC oil pressure switch, the VTEC solenoid valve and the ECM.

7. Turn the ignition switch OFF.

8. Remove the VTEC oil pressure switch (A) and install the special tools as shown, then install the VTEC oil pressure switch (A) to the oil pressure gauge adapter (B).

NOTE: Install the part in the reverse or order of removal with a new O-ring.

 

graphic

 

9. Disconnect the VTEC solenoid valve 2P connector.

10. Start the engine. Hold the engine speed at 3,000 RPM with no load (in neutral) until the radiator fan comes on, then let it idle.

11. Attach the battery positive terminal to VTEC solenoid valve 2P connector terminal No. 2.

12. Start the engine, then connect the battery negative terminal to VTEC solenoid valve 2P connector terminal No. 1, and check the oil pressure at an engine speed of 3,000 RPM.

Is the oil pressure above 390 kPa (4.0 kgf/cm 2 , 57 psi)?

YES: Go to step 13.

NO: Inspect the VTEC solenoid valve

13. Disconnect the VTEC oil pressure switch 2P connector.

14. At VTEC oil pressure switch side, check for continuity between VTEC oil pressure switch terminals No. 1 and No. 2 in the condition of step 12.

 

graphic

 

Is there continuity?

YES: Replace the VTEC oil pressure switch.

NO: Go to step 15.

15. Turn the ignition switch OFF.

16. Disconnect the battery terminals from the VTEC solenoid valve terminal connector.

17. Disconnect ECM/PCM connector B (24P).

18. Check for continuity between ECM connector terminal B9 and body ground.

 

graphic

 

Is there continuity?

YES: Repair short in the wire between the ECM (B9) and the VTEC oil pressure switch.

NO: Go to step 19.

19. Check for continuity between VTEC solenoid valve 2P connector terminal No. 1 and body ground.

 

graphic

 

Is there continuity?

YES: Go to step 20.

NO: Repair open in the wire between the VTEC solenoid valve and G101.

20. Check for continuity between ECM connector terminal B15 and body ground.

 

graphic

 

Is there continuity?

YES: Repair short in the wire between the ECM (B15) and the VTEC solenoid valve.

NO: Go to step 21.

21. Connect the VTEC solenoid valve 2P connector terminal No. 2 and body ground with a jumper wire.

 

graphic

 

22. Check for continuity between ECM connector terminal B15 and body ground.

 

graphic

 

Is there continuity?

YES: Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.

NO: Repair open in the wire between the ECM (B15) and the VTEC solenoid valve.

 

 

 

 

 

 

 

 

 

 

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