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Home >> Buick >> 1996 >> LeSabre Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1442 - EVAP Emission System Vacuum Switch Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. Turn ignition on, engine off. Using scan tool, command EVAP purge solenoid on, while monitoring EVAP VACUUM SW on ENG 2 data list. If scan tool displays NO PURGE, go to next step. If scan tool does not display NO PURGE, go to step 4).
  3. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data for DTC P1442. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1442 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1442 FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Disconnect EVAP vacuum switch harness connector. Connect a jumper wire across EVAP vacuum switch harness connector terminals. Using scan tool, read EVAP VACUUM SW. If scan tool displays NO PURGE, go to step 6). If scan tool does not display NO PURGE, go to next step.
  5. Check for open or short to ground in EVAP vacuum switch signal circuit between EVAP vacuum switch and PCM. Check for open EVAP vacuum switch ignition feed circuit. Check for faulty EVAP vacuum switch signal circuit connection at PCM. If a problem is found, repair as necessary and go to step 11). If no problem is found, go to step 7).
  6. Check for faulty connection at EVAP vacuum switch. If faulty connection is found, repair as necessary and go to step 11). If connection is okay, go to step 8).
  7. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to step 11).
  8. Check EVAP purge hose for restriction between EVAP canister and EVAP vacuum switch. If restriction is found, repair as necessary and go to step 11). If no restriction is found, go to next step.
  9. Check fuel tank vapor line for restriction between EVAP canister and fuel tank. If restriction is found, repair as necessary and go to step 11). If no restriction is found, go to next step.
  10. Replace EVAP vacuum switch and go to next step.
  11. Clear DTCs. Turn ignition on, engine off. Using scan tool, monitor EVAP VACUUM SW on ENG 2 data list. If scan tool displays NO PURGE, repair is complete. If scan tool does not display NO PURGE, return to step 2).
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