DTC P0139: Secondary Ho2S-2 Sensor Slow Response

WARNING: This page is about a different car, the 2000 Honda Prelude. However, it is still accessible from the selected car via links, so may be relevant.

Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS in SELF-DIAGNOSTICS - INTRODUCTION article. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Using scan tool, check HO2S-2 output voltage with engine speed at 3000 RPM. If 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 appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If voltage stays at 0.3-0.6 volt for two minutes, replace HO2S-2.