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DTC P1259: VTEC Pressure Switch Or Solenoid Valve Circuits

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES . Start engine and run 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 greater than 4000 RPM. Hold that engine RPM for at least 2 seconds. If DTC P1259 is not repeated during first road test, repeat road test 2 more times.
  2. If DTC P1259 sets, go to next step. If DTC P1259 does not set, problem is intermittent, system is functioning properly at this time. Check for poor connections or loose wires at VTEC pressure switch, solenoid valve and PCM connectors. See the WIRING DIAGRAMS article. Repair as necessary.
  3. Turn ignition off. Disconnect VTEC pressure switch 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.
  4. Turn ignition on. Measure voltage between ground and VTEC pressure switch harness connector terminal No. 1 (Blue/Black wire). If about 12 volts exists, go to next step. If about 12 volts does not exist, inspect for open or short to ground in Blue/Black wire between VTEC pressure switch and PCM. See the WIRING DIAGRAMS article. If wire is okay, substitute a known-good PCM and recheck. If symptom or DTC is gone, replace original PCM.
  5. Measure voltage across VTEC pressure switch harness connector terminals. If about 12 volts exists, turn ignition off and go to next step. If about 12 volts does not exist, repair open in Brown/Black wire between VTEC pressure switch and PCM 32-pin connector terminals No. 10 and No. 23. See the WIRING DIAGRAMS article. If wire is okay, substitute a known-good PCM and recheck.
    CAUTION: When checking VTEC oil pressure, keep measuring time as short as possible (less than one minute) because engine in running with no load.
  6. Remove VTEC pressure switch and install Pressure Gauge Adaptor (07NAJ-P07010A) and oil pressure gauge. Reinstall VTEC pressure switch and connect tachometer. Start engine and warm to operating temperature. Check oil pressure at engine speeds of 1000, 2000 and 3000 RPM. If oil pressure is more than 7 psi, go to next step. If oil pressure is 7 psi or less, inspect VTEC solenoid valve filter and valve plunger for clogging and smooth operation. Repair or replace as necessary.
  7. Turn ignition off and disconnect VTEC solenoid valve 2-pin connector. Using jumper wire, attach battery voltage to VTEC solenoid valve terminal Green/White wire. Start engine and check oil pressure at 3000 RPM. If oil pressure is more than 57 psi, go to next step. If oil pressure is 57 psi or less, inspect VTEC solenoid valve filter and valve plunger for clogging and smooth operation. Repair or replace as necessary.
  8. Turn ignition off. Reconnect VTEC pressure switch. Start engine. With battery voltage still connected to VTEC solenoid valve, measure voltage between PCM 31-pin connector terminal No. 15 (Blue/Black wire) and PCM 32-pin connector terminal No. 10 (Black wire) or No. 23 (Black wire). See Figure. If about 12 volts exists at an engine speed greater than 4000 RPM, go to next step. If about 12 volts does not exist at an engine speed greater than 4000 RPM, replace VTEC pressure switch.
  9. 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.
  10. Check for continuity between VTEC solenoid harness connector terminal and PCM 32-pin connector terminal No. 8 (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 harness connector terminal and PCM connector. See the WIRING DIAGRAMS article.
  11. Check for continuity between ground and VTEC solenoid harness connector terminal. If continuity does not exist, substitute a known-good PCM and recheck. If symptom or DTC is gone, replace original PCM. If continuity exists, repair short to ground in Green/Yellow wire between VTEC solenoid harness connector terminal and PCM connector. See the WIRING DIAGRAMS article.
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