DTC P1259: VTEC System Malfunction

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.
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.
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.
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.
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.
Turn ignition off. Disconnect VTEC solenoid valve connector. Measure continuity between VTEC solenoid valve connector terminal No. 1 (Brown/Black wire) and ground. If 14-30 ohms are present, go to next step. If 14-30 ohms are not present, replace VTEC solenoid valve.
Remove VTEC pressure switch. Install Pressure Gauge Adaptor (07NAJ-P07010A) and oil pressure gauge. Reinstall VTEC pressure switch. Reconnect VTEC solenoid valve and VTEC pressure switch connectors. Connect tachometer. Start and warm engine to normal operating temperature. 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 greater than 7 psi (.5 kg/cm² ), inspect VTEC solenoid valve for proper operation. See SYSTEM & COMPONENT TESTING article.
Turn ignition off. Disconnect VTEC solenoid valve connector. Connect battery voltage to solenoid valve connector terminal. Start engine and check oil pressure at 3000 RPM. If oil pressure is greater than 57 psi, (4 kg/cm² ), go to next step. If oil pressure is less than 57 psi (4 kg/cm² ), inspect VTEC solenoid valve for proper operation. See SYSTEM & COMPONENT TESTING article.
With battery voltage connected to VTEC solenoid valve, measure voltage between PCM 31-pin connector terminal C10 (Blue/Black wire) and ground. If battery voltage is present when engine speed is greater than 4000 RPM, go to next step. If battery voltage is not present when engine speed is greater than 4000 RPM, replace VTEC pressure switch.
Ensure ignition is off, Measure continuity of Green/Yellow wire between VTEC solenoid valve connector ant PCM 25-pin connector terminal No. 3. If continuity is present, go to next step. If continuity is not present, repair open circuit in Green/Yellow wire.
Measure continuity between VTEC solenoid valve connector and ground. If continuity is present, repair short circuit in Green/Yellow wire between 25-pin PCM connector terminal No. 12 and ground. If continuity is not present, substitute a known-good PCM and recheck. If symptom or DTC is gone, replace original PCM.