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DTC P1259: VTEC System Malfunction

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and run with no load 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 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, VTEC solenoid valve and PCM 25-pin and 31-pin connectors. See WIRING DIAGRAMS article.
  3. Turn ignition off. Disconnect VTEC pressure switch connector. Check for continuity between VTEC pressure switch connector 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 (Brown/Black wire). If about 12 volts exists, go to next step. If about 12 volts does not exist, check for an open or short to ground in Blue/Black wire between PCM 31-pin connector terminal No. 10 and VTEC pressure switch. If wire is okay, substitute a known-good PCM and recheck. If symptom or DTC is gone, replace original PCM.
  5. Measure voltage between VTEC pressure switch harness connector terminals. If about 12 volts exists, go to next step. If about 12 volts does not exist, repair open in Brown/Black wire between VTEC pressure switch and ground connector located at right rear of engine.
  6. Turn ignition off. Remove VTEC pressure switch. Install Pressure Gauge Adaptor (07NAJ-P07010A ) and oil pressure gauge. Reinstall VTEC pressure switch Connect tachometer. Start engine and warm to operating temperature (cooling fan comes on). Check oil pressure at engine speeds of 1000, 2000 and 3000 RPM. Keep measuring time as short as possible. If oil pressure is less than 7 psi (.5 kg/cm2 ), go to next step. If oil pressure is not less than 7 psi (.5 kg/cm2 ), inspect VTEC solenoid valve for proper operation. See SYSTEM/COMPONENT TESTS article.
  7. Turn ignition off. Disconnect VTEC solenoid valve connector. Connect a fused jumper between battery positive terminal and VTEC solenoid valve. Start engine and check oil pressure at an engine speed of 3000 RPM. If pressure is more than 36 psi (2.5 kg/cm2 ), go to next step. If pressure is not more than 36-psi (2.5 kg/cm2 ), inspect VTEC solenoid valve for proper operation. See SYSTEM/COMPONENT TESTS article.
  8. Turn ignition off. Reconnect VTEC pressure switch connector and start engine. Connect a fused jumper wire between positive battery terminal to VTEC solenoid valve terminal. Backprobing, measure voltage between PCM 31-pin connector terminal No. 10 (Blue/Black wire) and PCM 25-pin connector terminal No. 2 or 10. Increase engine speed to 4000 RPM. If about 12 volts exists, go to next step. If about 12 volts do not exist, replace VTEC pressure switch.
  9. Turn ignition off. Disconnect jumper from positive battery terminal and VTEC solenoid valve. Check for continuity between ground and VTEC solenoid valve harness connector terminal. If resistance is 14-30 ohms, go to next step. If resistance is not 14-30 ohms, replace VTEC solenoid valve.
  10. Backprobing, check for continuity between VTEC solenoid valve connector terminal and PCM 25-pin connector terminal No. 12 (Green/Yellow wire). If continuity exists, go to next step. If continuity does not exist, repair open in Green/Yellow wire between PCM 25-pin connector and VTEC solenoid valve connector.
  11. Check for continuity between ground and VTEC solenoid valve connector terminal. If continuity exists, repair short in Green/Yellow wire between PCM 25-pin connector terminal No. 12 and VTEC solenoid valve connector. If continuity does not exist, substitute a known-good PCM and recheck. If symptom or DTC is gone, replace original PCM.
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