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Home >> Nissan-Datsun >> 2003 >> Frontier Base, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> Engine Control Systems >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0456: EVAP Control System Very Small Leak (Negative Pressure Check) Or DTC P1456: EVAP Control System Very Small Leak (Positive Pressure Check) >> Diagnostic Procedure
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Diagnostic Procedure

  1. Ensure fuel cap is original equipment. Attempt to turn fuel cap clockwise. If fuel cap was tightened properly, go to next step. If fuel cap was not tightened properly, clean fuel cap and filler neck with compressed air. Reinstall cap and tighten until ratcheting sound is heard.
  2. While removing fuel cap, listen for air escaping from fuel tank. If air escaped from fuel tank, go to step  4 . If air did not escape from fuel tank, go to next step.
  3. Using a suitable hand vacuum/pressure pump with Fuel Filler Cap Adapter (MLR-8382), apply pressure and vacuum to fuel cap. Fuel cap vacuum relief valve should open when pressure reaches 2.22-2.90 psi (15.3-20.0 kPa) and when vacuum reaches 0.98-1.78 in. Hg (3.3-6.0 kPa). If operation is as specified, go to next step. If operation is not as specified, replace fuel cap.
  4. Connect EVAP Service Port Adapter (J41413-OBD) to EVAP service port. See Figure or Figure . Connect a suitable pressure pump to adapter. DO NOT use compressed air. If using CONSULT-II, go to next step. If using generic scan tool, go to step  6 .
  5. Turn ignition on. Select EVAP SYSTEM CLOSE of WORK SUPPORT mode with CONSULT-II. Press START. Observe pressure indicator on CONSULT-II. Apply pressure to EVAP system until pressure indicator reaches middle of bar graph. DO NOT exceed 0.6 psi (4.12 kPa) of pressure. Using Leak Detector (J41416), locate EVAP leak. See VACUUM DIAGRAMS article. If a leak is found, repair as necessary. If no leak is found, go to step  7 .
  6. Turn ignition off. Disconnect EVAP-CVCV and vacuum cut valve by-pass valve harness connectors. See Figure . Using jumper wires, apply battery voltage to EVAP-CVCV and vacuum cut valve by-pass valve terminals. See Figure . Apply 0.2-.4 psi (1.38-2.76 kPa) of pressure to EVAP service port. DO NOT exceed 0.6 psi (4.12 kPa) of pressure. Remove pressure pump from EVAP service port. Using Leak Detector (J41416), locate EVAP system leak. See VACUUM DIAGRAMS article. If a leak is found, repair as necessary. If no leak is found, go to next step.
    7. CAUTION: DO NOT disassemble water separator.
  7. Remove water separator and inspect for cracks or blockage. With water separator port "A" plugged, blow air into port "B". See Figure . Air should flow out of port "C". With port "C" plugged, blow air into port "B". Air should flow out of port "A". If operation is as specified, go to next step. If operation is not as specified, replace water separator.
  8. Check EVAP-CVCV, "O" ring and circuit by performing appropriate DTC CONFIRMATION TEST under DTC P1448: EVAP CANISTER VENT CONTROL VALVE OPEN  . If problem is found, repair as necessary. If problem is not found, go to next step.
  9. Remove EVAP canister with EVAP-CVCV attached. Attempt to drain water from EVAP canister. If water does not drain from EVAP canister, go to step  11 . If water drains from EVAP canister, weigh EVAP canister with EVAP-CVCV attached. If weight is more than 4.0 lbs. (1.8 kg), go to next step. If weight is less than 4.0 lbs. (1.8 kg), go to step  11 .
  10. Inspect EVAP canister for damage. Replace, if necessary. Also, check hose between water separator and EVAP canister for blockage or poor connection. If problem is found, repair as necessary. If problem is not found, go to next step.
  11. If using CONSULT-II, go to next step. If using generic scan tool, go to step  13 .
  12. Disconnect EVAP-CPVCSV hose from EVAP service port. Start engine. Perform PURG VOL CONT/V in ACTIVE TEST mode with CONSULT-II. Press Qu on CONSULT-II screen to increase PURG VOL CONT/V opening to 100 percent. Check for vacuum at disconnected hose while increasing engine speed to 2000 RPM. If vacuum exists, go to step  16 . If vacuum does not exist, go to step  14 .
  13. Start engine and warm to normal operating temperature. Turn ignition off. Disconnect EVAP-CPVCSV hose from EVAP service port. Start engine and let it idle for at least 80 seconds. While quickly increasing engine speed to 2000 RPM, check for vacuum at EVAP-CPVCSV hose. If vacuum exists, go to step  17 . If vacuum does not exist, go to next step.
  14. Check vacuum hoses for clogging or disconnection. See VACUUM DIAGRAMS article. If problem is found, repair as necessary. If problem is not found, go to next step.
  15. If using CONSULT-II, go to next step. If using generic scan tool, go to step  17 .
  16. Start engine. Perform PURG VOL CONT/V in ACTIVE TEST mode with CONSULT-II. Engine speed should vary according to valve opening. If operation is as specified, go to step  18 . If operation is not as specified, go to next step.
  17. Turn ignition off. Remove EVAP-CPVCSV. Using jumper wires, apply battery voltage to EVAP-CPVCSV terminals. See Figure . Air should flow between ports "A" and "B". Remove jumper wires. Air should not flow. If operation is as specified, go to next step. If operation is not as specified, replace EVAP-CPVCSV.
  18. Check Fuel Tank Temperature (FTT) sensor. See appropriate DIAGNOSTIC PROCEDURE under DTC P0181, DTC P0182 OR DTC P0183: FUEL TANK TEMPERATURE SENSOR  . If FTT sensor is okay, go to next step. If FTT sensor is not okay, replace FTT sensor.
    19. CAUTION: Replace EVAP-CSPS if it has been dropped from a height of more than 20" (.5 m) onto a hard surface such as concrete. On 2.4L models, do not apply more than 5.91 in. Hg of vacuum to EVAP-CSPS.
    CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  19. Remove EVAP-CSPS with its harness connector connected. See Figure . Turn ignition on. Measure voltage between ground and ECM terminal No. 62 (Yellow wire) by backprobing. See Figure or Figure . See Figure . On 2.4L models, voltage should be 3.0-3.6 volts with no vacuum applied. Apply 2.76 in. Hg of vacuum to EVAP-CSPS. Voltage should be 0.4-0.6 volt. On 3.3L models, voltage should be 1.8-4.8 volts with no vacuum applied. Apply 7.87 in. Hg of vacuum to EVAP-CSPS. Voltage should be 1.0-1.4 volts less than voltage measured with no vacuum applied. On all models, if voltage is as specified, go to next step. If voltage is not as specified, replace EVAP-CSPS.
  20. Check EVAP purge line at fuel tank and EVAP canister for leaks or improper connection. See VACUUM DIAGRAMS article. If a problem is found, repair as necessary. If problem is not found, clean purge line with compressed air, then go to next step.
  21. Check fuel level sensor. See appropriate DIAGNOSTIC PROCEDURE under DTC P0460: FUEL LEVEL SENSOR SLOSH  . If fuel level sensor is okay, go to next step. If fuel level sensor is not okay, replace fuel level sensor.
  22. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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