DTC P1259: VTEC System Malfunction (2000-2003 models)

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 adapter 07MAJ-PY40120

1. Reset the engine control module (ECM) (see HOW TO RESET THE ECM ).
2. Check the engine oil level, and refill if necessary.
3. Start the engine. Hold the engine speed at 3,000 RPM without load (in neutral) until the radiator fan comes on.
4. Road test the vehicle:

   Accelerate in 1st gear to an engine speed over 6,000 RPM. Hold that engine speed for at least 2 seconds. If DTC P1259 is not repeated during the first road test, repeat this test two more times.

   Is DTC P1259 indicated? 

   1. YES -  Go to step 5.
   2. NO -  Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the rocker arm oil control solenoid (VTEC solenoid valve), the rocker arm oil pressure switch (VTEC oil pressure switch), and the ECM.
5. Turn the ignition switch OFF.
6. Disconnect the rocker arm oil pressure switch (VTEC oil pressure switch) 2P connector.
7. At the switch side, check for continuity on the rocker arm oil pressure switch (VTEC oil pressure switch) between rocker arm oil pressure switch (VTEC oil pressure switch) 2P connector terminals No. 1 and No. 2.
   Fig 1: Checking Continuity On Rocker Arm Oil Pressure Switch (VTEC Oil Pressure Switch)

   Courtesy of AMERICAN HONDA MOTOR CO., INC.

   Is there continuity? 

   1. YES -  Go to step 8.
   2. NO -  Replace the rocker arm oil pressure switch (VTEC oil pressure switch).
8. Turn the ignition switch ON (II).
9. Measure the voltage between the rocker arm oil pressure switch (VTEC oil pressure switch) harness 2P connector terminal No. 1 and body ground.
   Fig 2: Measuring Voltage Between Rocker Arm Oil Pressure Switch

   Courtesy of AMERICAN HONDA MOTOR CO., INC.

   Is there battery voltage? 

   1. YES -  Go to step  14.
   2. NO -  Inspect for an open or short to ground in the wire between the rocker arm oil pressure switch (VTEC oil pressure switch) and the ECM (C10). If the wire is OK, substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck.
10. Measure voltage between ECM connector terminal C10 and body ground.
    Fig 3: Measuring Voltage Between ECM Connector Terminal C10 And Body Ground

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES -  Repair open in the wire between the rocker arm oil pressure switch (VTEC oil pressure switch) and the ECM.
    2. NO -  Go to step 11.
11. Turn the ignition switch OFF.
12. Disconnect the ECM connector C (31P).
13. Check for continuity between ECM connector terminal C10 and body ground.
    Fig 4: Checking Continuity Between ECM Connector Terminal C10 And Body Ground

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES -  Repair short in the wire between the rocker arm oil pressure switch (VTEC oil pressure switch) and the ECM(C9).
    2. NO -  Substitute a known-good ECM (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES ) and recheck. If the symptom/indication goes away, replace the original ECM (see ECM REPLACEMENT ).
14. Measure voltage between rocker arm oil pressure switch (VTEC oil pressure switch) 2P connector terminals No. 1 and No. 2.
    Fig 5: Measuring Voltage Between Rocker Arm Oil Pressure Switch

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there battery voltage? 

    1. YES -  Go to step 15.
    2. NO -  Repair open in the wire between the rocker arm oil pressure switch (VTEC oil pressure switch) and G101.
15. Turn the ignition switch OFF.
16. Disconnect the rocker arm oil control solenoid (VTEC solenoid valve) 1P connector.
17. At the valve side, measure resistance between the rocker arm oil control solenoid (VTEC solenoid valve) 1P connector and body ground.
    Fig 6: Disconnecting Rocker Arm Oil Control Solenoid (VTEC Solenoid Valve) 1P Connector

    Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there 14-30 Ω ? 

    1. YES -  Go to step 18.
    2. NO -  Replace the rocker arm oil control solenoid (VTEC solenoid valve).
18. Remove the rocker arm oil pressure switch (VTEC oil pressure switch) (A) and install the special tools as shown, then reinstall the rocker arm oil pressure switch (VTEC oil pressure switch).
    NOTE: Install the part in the reverse order of removal with a new O-ring.