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DTC P1259: VTEC System Malfunction

  1. Check engine oil level, refill if necessary. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DIAGNOSTIC TROUBLE CODES . Start engine and run at 4000 RPM, with no load and transmission in Park or Neutral, until radiator fan comes on. On MDX, road test vehicle in position "2" at more than 4,500 RPM and hold for more than 2 seconds. On 3.2CL and 3.2TL, road test vehicle in position "1" at more than 4,000 RPM and hold for more than 2 seconds. If DTC P1259 comes on, go to next step. If DTC P1259 does not come on, problem is intermittent. System is okay at this time. Check for poor connection(s) or loose wire(s) between PCM 25-pin harness connector and VTEC solenoid valve harness connector.
  2. Turn ignition off. Disconnect VTEC oil pressure switch 2-pin connector. Check continuity at VTEC oil pressure switch 2-pin connector terminals No. 1 (Blue/Black wire) and No. 2 (Brown/Yellow wire). See WIRING DIAGRAMS article. If continuity is present, go to next step. If continuity is not present, replace VTEC oil pressure switch.
  3. Turn ignition on. Measure voltage between ground and VTEC oil pressure switch 2-pin harness connector terminal No. 1 (Blue/Black wire). On MDX if battery voltage is present, go to step  7. On 3.2CL and 3.2TL, if battery voltage is present, go to next step. On MDX, if battery voltage is not present, go to step  5. On 3.2CL and 3.2TL, if battery voltage is not present, Check for open or short in Blue/Black wire between PCM 25-pin harness connector terminal No. 10 and VTEC oil pressure switch 2-pin harness connector terminal No. 1. If wire is okay, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  4. Measure voltage between VTEC oil pressure switch 2-pin harness connector terminals No. 1 (Blue/Black wire) and No. 2 (Brown/Yellow wire). See WIRING DIAGRAMS article. On MDX, if battery voltage is present, go to step  6. On 3.2CL and 3.2TL If battery voltage is present, go to step  8. On MDX, if battery voltage is not present, go to next step. On 3.2CL and 3.2TL, if battery voltage is not present, repair open in Brown/Yellow wire between ground and VTEC oil pressure switch 2-pin harness connector terminal No. 2. If Brown/Yellow wire is okay, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  5. Measure voltage between ground and PCM 31-pin harness connector terminal No. 10 (Blue/Black wire). If battery voltage is not present, go to next step. If about battery voltage is present, repair open in Blue/Black wire between PCM 31-pin harness connector terminal No. 10 and VTEC oil pressure switch 2-pin harness connector terminal No. 1.
  6. Turn ignition off. Disconnect PCM 31-pin harness connector. Check continuity of Blue/Black wire between ground and PCM 31-pin harness connector terminal No. 10. If continuity is present, repair short in Blue/Black wire between PCM 31-pin harness connector terminal No. 10. See WIRING DIAGRAMS article. If continuity is not present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  7. Measure voltage between terminals No. 1 (Blue/Black wire) and No. 2 (Brown/Yellow wire) of VTEC oil pressure switch 2-pin harness connector. If battery voltage is present, go to step  6. If battery voltage is not present, repair open in Brown/Yellow wire between ground and VTEC oil pressure switch terminal No. 2.
  8. Turn ignition off. Disconnect VTEC solenoid valve connector. Check resistance between ground and VTEC solenoid valve connector. If 14-30 ohms is present, go to next step. If 14-30 ohms is not present, inspect VTEC solenoid valve. See RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article.
  9. Remove VTEC oil pressure switch. Install special tools No. 07NAJ-P07010A, 07406-0070300 and 07MAJ-PY40120. See Fig 1. Reinstall VTEC oil pressure switch. Reconnect VTEC solenoid valve connector and VTEC oil pressure switch 2-pin harness connector. Start engine and run at 3,000 RPM with no load and transmission in Park or Neutral, until radiator fan comes on. Check oil pressure at 1,000, 2,000 and 3,000 RPM. Checks should be done in under one minute because of engine running with no load. If oil pressure is below 49 kPa, go to next step. If oil pressure is not as specified, test VTEC solenoid valve. See RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article.
  10. Turn ignition off. Disconnect VTEC solenoid valve connector. Using fused jumper wire, connect battery voltage to VTEC solenoid valve connector terminal. Start engine and check oil pressure at 3,000 RPM. If pressure is more than 390 kPa, go to next step. If oil pressure is not as specified, test VTEC solenoid valve. See RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article.
  11. With battery voltage still connected to VTEC solenoid valve connector terminal, (back probing) measure voltage between ground and PCM 31-pin harness connector terminal No. 10 (Blue/Black wire) See WIRING DIAGRAMS article. If battery voltage is present at more than 4,500 RPM on MDX or more than 4,000 RPM on 3.2CL and 3.2TL, go to next step. If battery voltage is not present at more than 4,500 RPM on MDX or more than 4,000 RPM on 3.2CL and 3.2TL, replace VTEC oil pressure switch.
  12. Turn ignition off. Disconnect fused jumper wire. Check continuity between PCM 25-pin harness connector terminal No. 12 and VTEC solenoid valve harness connector terminal. If continuity is present, go to next step. If continuity is not present, Repair open in Light Green/Yellow wire on MDX or Green/Yellow wire on 3.2CL and 3.2TL, between PCM 25-pin harness connector terminal No. 12 and VTEC solenoid valve harness connector terminal.
  13. Check continuity between ground and VTEC solenoid valve harness connector terminal. If continuity is present, repair short in Light Green/Yellow wire on MDX or Green/Yellow wire on 3.2CL and 3.2TL, between PCM 25-pin harness connector terminal No. 12 and VTEC solenoid valve harness connector terminal. If continuity is not present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
Fig 1: Identifying VTEC Special Tools
G00032251Courtesy of AMERICAN HONDA MOTOR CO., INC.
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