Both oxygen sensors are new and the one is still showing a P0135 code. on 1996 Lexus LX450

The ECU was checked and is working properly. Where do I look next?

Asked by for the 1996 Lexus LX450
Either you have gotten a new sensor with a bad heater circuit or there is likely a wiring issue between the sensor and ECU. The ECU monitors the resistance in the heater circuit and if its out of range it sets that code for bank 1 sensor 1. Its looking for 11-16 ohms on that circuit.