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Home >> GMC >> 1999 >> Forward Control 6.5 F, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - DTC P1273-P1536 >> DTC P1441 >> DTC P1441: EVAP System Flow During Non-Purge (3.8L "F" Body) >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Check for disconnected vacuum or purge lines. Check for missing or loose fuel filler cap. Repair as necessary. Check if DTC P0443 or P0449 is also set. If DTC(s) are set, diagnose affected DTCs first. If DTC(s) are not set and purge lines and fuel filler cap are okay, go to next step.
  3. Turn ignition off. Remove EVAP canister line from EVAP canister purge valve to relieve fuel tank pressure. Turn ignition on, with engine off. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays zero in. H2O, go to next step. If scan tool does not display zero in. H2O, go to step  12.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J-41413). Reconnect EVAP canister lines. Install Fuel Tank Cap Adapter (J-41415-0) between filler neck and fuel filler cap. Connect EVAP Station to fuel tank cap adaptor. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data for DTC P1441. Clear DTCs. Using scan tool, select EVAP PURGE/SEAL function and select seal option to seal EVAP system. Attempt to pressurize EVAP system to 5 in. H2O using diagnostic station. If specified pressure is achieved, go to next step. If specified pressure cannot be achieved, to step  6.
  5. Maintain EVAP system pressure at 5 in. H2O. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays 5 in. H2O, see DIAGNOSTIC AIDS . If scan tool does not display 5 in. H2O, go to step  10.
  6. Check EVAP purge vacuum and source line routing and connections at EVAP purge solenoid. If no problem is found, go to next step. If a problem is found, go to step  9.
  7. Connect vacuum gauge from EVAP Pressure/Purge Diagnostic Station to canister side of purge valve/solenoid. Turn ignition on, with engine off. Using scan tool, select EVAP PURGE/SEAL function and select seal option to seal EVAP system. Start and operate engine at idle. Increase engine speed from 1200-1500 RPM and observe vacuum level. If vacuum level is about zero in. H2O, see DIAGNOSTIC AIDS . If vacuum level is not about zero in. H2O, go to next step.
  8. Replace EVAP canister purge valve/solenoid. Check for carbon release into EVAP system. After repairs, go to step  13.
  9. Correct EVAP line routing and connections as necessary. After repairs, go to step  13.
  10. Check for restricted fuel tank vapor line or EVAP purge line. If a problem is found, go to step  13. If no problems were found, go to DTC P0452 test.
  11. Check for kinked or restricted canister purge line between EVAP canister purge valve and canister. Repair as necessary. After repairs, go to step  13.
  12. Turn ignition off. Remove EVAP canister line from fuel tank or EVAP canister to relieve fuel tank pressure. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure. If fuel tank pressure is about zero in. H2O, go to step  11. If fuel tank pressure is not about zero in. H2O, go to DTC P0453 test.
  13. Reconnect all EVAP hardware that were disconnected. Turn ignition on, with engine off. Using scan tool in PURGE/SEAL function, select seal option to seal EVAP system. Pressurize system to 15 in. H2O or higher by slowly turning EVAP Service Station rotary switch to PRESSURE position. Observe pressure on gauge with rotary switch in OFF/HOLD position. If EVAP pressure decreases to less than 10 in. H2O within 2 minutes, repeat step  3. If EVAP pressure does not decrease to less than 10 in. H2O, system is okay.
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