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Home >> Chevrolet >> 1997 >> Venture LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1442 - EVAP Vacuum Switch Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, observe EVAP VACUUM SW. display. If display reads NO PURGE, go to next step. If display does not read NO PURGE, go to step 4).
  3. Review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1442 until DTC P1442 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Disconnect EVAP purge switch connector. Connect a jumper wire between EVAP purge switch connector terminals. Observe EVAP VACUUM SW display. If reading indicates no purge, go to step 6). If reading does not indicate no purge, go to next step.
  5. Check for an open or short to ground in EVAP vacuum switch signal circuit between EVAP vacuum switch and PCM. Check for an open EVAP vacuum switch ignition feed circuit. Check for poor EVAP vacuum switch signal circuit connection at PCM. Repair as necessary. After repairs, go to step 11). If no problem is found, go to step 7).
  6. Check for poor connection at EVAP vacuum switch connector. Repair as necessary. After repairs, go to step 11). If connection is okay, go to step 8).
  7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 11).
  8. Check EVAP purge hose for restriction between canister and vacuum switch. Repair as necessary. After repairs, go to step 11). If no restriction is found, go to next step.
  9. Check fuel tank vapor line for restriction between canister and fuel tank. Repair as necessary. After repairs, go to step 11). If no restriction is found, go to next step.
  10. Replace EVAP vacuum switch. After replacing switch, go to next step.
  11. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, select ENG 1 data list. Observe EVAP VACUUM SW display. If reading indicates no purge, repair is complete. If reading does not indicate no purge, repeat step 2).
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