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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: If DTC P0440, P0442, P0446 or P0496 is set, EVAP special functions on scan tool will not be allowed. Clear DTCs before performing these tests.
  1. Turn ignition on, engine off. Ensure fuel level is 2.4-13.4 gallons. Remove fuel cap. Using scan tool, monitor fuel tank pressure sensor. If voltage is 1.4-1.6 volts, go to step  3 . If voltage is not 1.4-1.6 volts, go to next step.
  2. If voltage is less than 0.2 volt, see DTC P0452: EVAP FUEL TANK PRESSURE SENSOR CIRCUIT - LOW VOLTAGE  . If voltage is 0.20-1.40 volts or 1.60-4.75 volts, replace FTP sensor. If voltage is more than 4.75 volts, see DTC P0453: EVAP FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE  .
  3. Install fuel cap. Clear ECM DTCs. Start engine and let idle. Using scan tool, perform EVAP PURGE/SEAL special function by commanding a 10 percent duty cycle to the EVAP purge solenoid. Using scan tool, monitor fuel tank pressure sensor. If voltage reaches 2.02 volts or greater within 8 seconds, fuel cap was not installed properly or fuel cap is leaking. If voltage does not reach 2.02 volts or greater within 8 seconds, go to next step.
  4. Turn ignition on, engine off. Using scan tool, seal the EVAP system by using EVAP PURGE/SEAL special function. Connect EVAP System Tester (J41750-A) to EVAP service port. Perform diagnostic process as described on the EVAP system tester to determine if leak is present. If the leak was identified, repair leak. Perform flowmeter test as described on the EVAP system tester to verify fix or run EVAP service bay test. If the leak was not identified, the problem is insufficient manifold vacuum to EVAP purge solenoid, or EVAP restriction between fuel level vent valve and EVAP purge solenoid. Check the following:

    For Insufficient Vacuum

    • Vacuum hose to EVAP purge solenoid for leaks.
    • Plugged throttle body vacuum port.
    • EVAP purge solenoid for a stuck closed valve. Use scan tool to command EVAP PURGE SOLENOID to a 20 percent duty cycle while listening for consistent clicking.

    For EVAP Restriction

    • EVAP canister restricted. With both purge and tank lines disconnected from EVAP canister, air should flow relatively freely each way through EVAP canister.
    • EVAP line kinked or crushed between the fuel level vent valve and EVAP canister, or between the EVAP canister and EVAP purge solenoid.
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