DTC P0139 - SECONDARY HO2S-2 SENSOR SLOW RESPONSE Isuzu Oasis I

Perform PCM reset procedure. See TESTS W/CODES - INTRODUCTION article. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Using OBD-II scan tool, check HO2S-2 output voltage with engine at 3000 RPM. If output voltage stays at 0.3-0.6 volt for two minutes, replace HO2S-2. If output voltage does not stay at 0.3-0.6 volt for two minutes, problem is intermittent. System is okay at this time. Check for poor connections or loose wires at HO2S-2 and PCM connectors. See WIRING DIAGRAMS article. Repair as necessary.