Replaced CAT and O2 sensors - P0138 keeps coming back

Question

2000 Honda Civic - has high mileage and cracked manifold.  I replaced the Manifold, Cat. Converter and both 02 sensors.  I keep getting P0138 code after driving for a little while - 20 minutes.  How do I diagnose?

Answer 1

P0138 High voltage problem in the secondary 02 sensor , Sensor 2 circuit

Rule out a  wiring problem , when the ECM detects a voltage high , this is a broken connection, or poor connection, Here a troubleshooting direction you can follow.