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Home >> Isuzu >> 1999 >> Trooper Part Time >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P1441: EVAP System Flow During Non-Purge (3.5L) >> Diagnostic Aids
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Diagnostic Aids

An intermittent may be caused by a cracked or punctured EVAP canister, damaged or disconnected vacuum, vent or purge line. Check for poor connection, rubbed-through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Monitor FUEL TANK VACUUM display while moving EVAP connections and related harnesses. Change in scan tool display will indicate area of fault. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. After performing OBD system check, go to next step.
  2. Turn ignition on, engine off. Check EVAP VACUUM SW display on scan tool. If EVAP VACUUM SW displays CLOSED, go to next step. If EVAP VACUUM SW does not display CLOSED, see DTC P1442: EVAP VACUUM SWITCH HIGH VOLTAGE DURING IGNITION ON (3.5L)  test.
  3. Run engine at idle. Observe EVAP VACUUM SW while commanding EVAP purge solenoid OFF with scan tool. If EVAP VACUUM SW displays CLOSED with EVAP purge solenoid commanded OFF, go to next step. If EVAP VACUUM SW does not display CLOSED with EVAP purge solenoid commanded OFF, go to step  5.
  4. Turn ignition on, engine off. Review and record scan tool FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS conditions as noted. Using scan tool, monitor STATUS THIS IGNITION for DTC P1441. If scan tool indicated DTC P1441 failed, go to next step. If scan tool indicates DTC P1441 did not fail, see DIAGNOSTIC AIDS .
  5. Turn engine off. Disconnect EVAP purge solenoid electrical connector. Start and idle engine. Observe EVAP VACUUM SW display on scan tool. If EVAP VACUUM SW displays CLOSED, go to next step. If EVAP VACUUM SW does not display CLOSED, go to step  7.
  6. Turn ignition off. Disconnect PCM connector. Check EVAP canister purge solenoid circuit (Black/Yellow wire) for a short circuit to ground. Repair wiring as necessary. If wiring is okay, replace PCM.
  7. Leave EVAP purge solenoid electrical connector disconnected. Disconnect vacuum signal hose from EVAP purge vacuum switch. Connect vacuum gauge to vacuum signal hose. Start and idle engine. Observe vacuum reading at vacuum signal hose. If vacuum is more than 5 inches H2 O, replace EVAP purge solenoid. If vacuum is 5 inches H2 O or less, replace EVAP vacuum switch.
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