I replaced the oxygen sensors with new ones; however, the new ones are still showing the code (from the code reader) like the old sensors: P0135. I have checked the ECU and it is functioning as it should. Would you please tell me the next step of where I should look in order to fix this code problem. Thank you.
P0135 is a "heater circuit" malfunction in the O2 sensor. This is usually a fused circuit. Check your Owners Manual to verify that it is fused, then check that fuse to make sure it isn’t blown ("something" caused the old one to fail, may have taken the fuse out with it). If that fuse is OK, you may have a wiring issue to the O2 sensor. A professional mechanic, like a certified technician from YourMechanic, can diagnose, inspect the heater circuit and repair this problem at your home or office.