Your Camry with the 1MZ-FE engine and a unique exhaust system, different from most versions.
According to your description, you only have narrowband O2 sensors in the exhaust system, which operate in the range from 0.1 to 0.9 volts. Such sensors are most often used in older generation cars. These trouble codes P0135 and P0155 indicate a malfunction in the oxygen sensor heater circuits. a broken heater leads to incorrect operation of the sensors, especially on a cold engine and more fuel is consumed.
you will need to purchase new wideband A/F sensors that are compatible with your model. you can view spare parts on globy.com or contact your Toyota dealer. After replacing the oxygen sensors, you will need to clear the error codes and perform testing to make sure the problems go away.
