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DTC P1259: VTEC Pressure Switch & Solenoid Valve

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS  . Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral, until radiator fan comes on. Road test vehicle. Accelerate in 1st gear to an engine speed more than 6000 RPM. Hold specified engine speed for at least 2 seconds. If DTC P1259 is not repeated during first road test, repeat road test 2 more times. If DTC P1259 is indicated, go to next step. If DTC P1259 is not indicated, problem is intermittent, system is okay at this time. Check for poor connections or loose wires between at VTEC pressure switch, solenoid valve and PCM connectors. See the WIRING DIAGRAMS article. Repair as necessary.
  2. Turn ignition off. Disconnect VTEC pressure switch 2-pin connector. Check for continuity between VTEC pressure switch terminals. If continuity exists, go to next step. If continuity does not exist, replace VTEC pressure switch.
  3. Turn ignition on. Check voltage between ground and VTEC pressure switch connector terminal No. 1 (Blue/Black wire). If approximately 12 volts exists, go to next step. If approximately 12 volts does not exist, inspect for an open or short to ground in Blue/Black wire between VTEC pressure switch and PCM 31-pin connector "C" terminal C15. See the WIRING DIAGRAMS article. If wire is okay, substitute a known-good PCM and recheck. If symptom or problem goes away, replace original PCM.
  4. Measure voltage between VTEC pressure switch connector terminals. If approximately 12 volts exists, turn ignition off and go to next step. If approximately 12 volts does not exist, repair open in wire between VTEC pressure switch and ground. See the WIRING DIAGRAMS article.
  5. Remove 10-mm oil pressure inspection bolt. Connect oil low pressure gauge. Connect tachometer. Start engine and warm to operating temperature. Because engine is running with no load, oil pressure must be checked within one minute. Check oil pressure at engine speeds of 1000, 3000 and 5000 RPM. If oil pressure is less than 7 psi, go to next step. If oil pressure is 7 psi or more, inspect VTEC solenoid valve filter/"O" ring and valve plunger for clogging and smooth operation. If filter/"O" ring is clogged, replace engine oil and oil filter. Repair/replace as necessary.
  6. Turn ignition off. Disconnect VTEC solenoid valve connector. Using fused jumper wire, attach battery voltage to VTEC solenoid valve Green/Yellow wire terminal. Start engine and check oil pressure at 5000 RPM. If oil pressure is more than 60 psi, go to next step. If oil pressure is not more than specified, inspect VTEC solenoid valve filter/"O" ring and valve plunger for clogging and smooth operation. If filter/"O" ring is clogged, replace engine oil and oil filter. Repair/replace as necessary.
  7. Turn ignition off. Reconnect VTEC pressure switch connector. Start engine. With battery voltage connected to VTEC solenoid valve, measure voltage between PCM connector terminals C15 and A10 or A23. See Figure . If approximately 12 volts exists at more than 5000 RPM, go to next step. If approximately 12 volts does not exist at more than 5000 RPM, replace VTEC pressure switch.
  8. Turn ignition off. Disconnect battery voltage from VTEC solenoid valve. Check for continuity between ground and VTEC solenoid valve terminal. If resistance is 14-30 ohms, go to next step. If resistance is not 14-30 ohms, replace VTEC solenoid valve.
  9. Check for continuity between VTEC solenoid valve connector terminal No. 1 and PCM 32-pin connector "A" terminal A8 (Green/Yellow wire). See Figure . If continuity exists, go to next step. If continuity does not exist, repair open in Green/Yellow wire between VTEC solenoid valve connector terminal and PCM connector. See the WIRING DIAGRAMS article.
  10. Check for continuity between ground and VTEC solenoid valve connector terminal No. 1. If continuity does not exist, substitute a known-good PCM and recheck. If symptom or problem goes away, replace original PCM. If continuity exists, repair short in Green/Yellow wire between VTEC solenoid valve connector terminal and PCM connector. See the WIRING DIAGRAMS article.
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