LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Isuzu >> 1997 >> Oasis LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P1459: EVAP Purge Flow Switch Malfunction
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P1459: EVAP Purge Flow Switch Malfunction

  1. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral, until radiator fan comes on. Allow engine to idle. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS  . Connect SCS service connector. Let engine idle. If DTC P1459 is indicated, go to next step. If DTC P1459 is not indicated, problem is intermittent, system is okay at this time. Check for poor connections or loose wires at EVAP purge flow switch or control box and PCM. See the WIRING DIAGRAMS article.
  2. Turn ignition off. Check EVAP system vacuum hoses for proper routing, leaks or restrictions. See the VACUUM DIAGRAMS article. Repair vacuum hoses as necessary. If vacuum hoses are okay, disconnect purge flow switch 2-pin connector. Check for continuity between PCM 32-pin connector "A" terminal A10 (Black wire) and PCM 31-pin connector "C" terminal C20 (Brown wire). See Figure . If continuity exists, go to next step. If continuity does not exist, replace EVAP purge flow switch.
  3. Disconnect PCM 31-pin connector "C". Check for continuity between EVAP purge flow switch connector terminal No. 1 (Brown wire) and terminal No. 2 (Black wire). If there is continuity, repair short to ground in Brown wire between PCM and EVAP purge flow switch. If continuity does not exist, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.
scientia non olet · About LEMON Manuals