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Home >> Acura >> 2001 >> 3.2CL Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1456: Evaporative Emission (EVAP) Control System >> Notes
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DTC P1456: Evaporative Emission (EVAP) Control System: Notes

  1. Inspect fuel filler cap. Cap must be Gray or Black OEM type on MDX or Gray OEM type on 3.2CL and 3.2TL, tightened at least three clicks and seal is okay. Replace as necessary. If fuel filler cap is okay, go to next step.
    NOTE: EVAP purge control solenoid valve may also be referred to as EVAP canister purge valve.
  2. Turn ignition off. Disconnect vacuum hose coming from EVAP purge control solenoid valve. Connect vacuum pump to now available port on EVAP purge control solenoid. Turn ignition on. Apply vacuum to hose. If valve does not hold vacuum, go to next step. If valve holds vacuum, EVAP purge control solenoid valve is okay. Go to step  5.
  3. Turn ignition off. Disconnect EVAP purge control solenoid valve 2-pin connector. Check continuity between ground and EVAP purge control solenoid valve 2-pin harness connector terminal (Red/Yellow wire). See WIRING DIAGRAMS article. Repair as necessary. If continuity is present, go to next step. If continuity is not present, replace EVAP purge control solenoid valve.
  4. Disconnect PCM 32-pin harness connector. Check continuity between ground and EVAP purge control solenoid valve 2-pin harness connector terminal (Red/Yellow wire). If continuity is present, repair short in Red/Yellow wire between EVAP purge control solenoid valve 2-pin harness connector terminal and PCM 32-pin harness connector terminal No. 6. If continuity is not present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  5. Disconnect vacuum hoses coming from EVAP 2-way valve. Connect vacuum pump to now available port on EVAP 2-way valve. Connect fused jumper wire between ground and PCM 32-pin harness connector terminal No. 3 (Orange/White wire) on MDX or (Blue wire) on 3.2CL and 3.2TL. Turn ignition on. Apply vacuum to hose. If valve holds vacuum, go to next step. If valve does not hold vacuum, go to step  8.
  6. Turn ignition off. Disconnect EVAP by-pass solenoid valve 2-pin connector. Check continuity between EVAP by-pass solenoid valve 2-pin harness connector terminal No. 2 (Orange/White wire) on MDX or (Blue wire) on 3.2CL and 3.2TL and ground. See WIRING DIAGRAMS article. Repair as necessary. If continuity is present, go to next step. If continuity is not present, repair open in (Orange/White wire) on MDX or (Blue wire) on 3.2CL and 3.2TL between PCM 32-pin harness connector terminal No. 3 and EVAP by-pass solenoid valve 2-pin harness connector terminal No. 2.
  7. Turn ignition on. Measure voltage between ground and EVAP by-pass solenoid valve 2-pin harness connector terminal No. 1 (Black/Yellow wire). If battery voltage is present, replace EVAP by-pass solenoid valve and "O" rings. If battery voltage is not present, repair open in Black/Yellow wire between EVAP by-pass solenoid valve 2-pin harness connector terminal No. 1 and fuse No. 6 (15-amp) in underdash fuse/relay box.
  8. Plug upper port of EVAP 2-way valve. Measure voltage between PCM 32-pin harness connector terminal No. 29 (Light Green wire) and 31-pin harness connector terminal No. 18 (Light Green/Yellow wire) on MDX or (Green/Black wire) on 3.2CL and 3.2TL while slowly applying vacuum. If voltage drops to about 1.5 volts and holds for at least 20 seconds, EVAP by-pass solenoid valve/EVAP 2-way valve is okay. Go to next step. If voltage does not drop to about 1.5 volts and hold, repair leakage from EVAP by-pass solenoid valve, EVAP 2-way valve, fuel tank pressure sensor and "O" rings.
  9. Disconnect vacuum hose from EVAP control canister filter. Connect vacuum pump to disconnected hose. Turn ignition on. Apply vacuum to hose with 5 strokes of vacuum pump. If valve holds vacuum, go to next step. If valve does not hold vacuum, EVAP control canister vent shut valve is okay. Go to ORVR VENT SHUT VALVE TEST .
  10. Turn ignition off. Disconnect EVAP control canister vent shut valve 2-pin connector. Check continuity between ground and EVAP control canister vent shut valve 2-pin connector terminal No. 2 (Light Green/White wire). See WIRING DIAGRAMS article. Repair as necessary. If continuity is present, go to next step. If continuity is not present, replace EVAP control canister vent shut valve and "O" ring.
  11. Disconnect PCM 32-pin harness connector. Check continuity between ground and EVAP control canister vent shut valve 2-pin harness connector terminal No. 2 (Light Green/White wire). If continuity is present, repair short in Light Green/White wire between PCM 32-pin harness connector terminal No. 4 and EVAP control canister vent shut valve 2-pin harness connector terminal No. 2. If continuity is not present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  12. Check fuel tank vapor control float and valve. See VAPOR CONTROL FLOAT TEST  and VAPOR CONTROL VALVE TEST  . Repair or replace as necessary. If float and valve function properly, go to next step.
  13. Tighten fuel cap 3 clicks. Connect scan tool to vehicle. Start and idle engine for 5 minutes. Using scan tool, check fuel tank pressure sensor reading. If fuel tank pressure sensor reading is greater than 4mmHg pressure or less than 4mmHg vacuum, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If fuel tank pressure sensor reading is not within specifications, check for leaks at following components:
    • Fuel tank.
    • Fuel filler cap.
    • Fuel filler pipe.
    • Fuel tank vapor control valve.
    • Fuel tank vapor recirculation valve.
    • Fuel tank vapor recirculation tube.
    • Fuel tank vapor signal tube.
    • Fuel tank vapor control vent tube.

    If necessary, repair or replace parts.

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