codes P0135 and P0155

This code refers to the front oxygen sensor on Bank 2. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0155. See also: P0135 (Bank 1).

Potential SymptomsYou will likely notice poor fuel economy the illumination of the MIL.

CausesA code P0155 may mean that one or more of the following has happened:

•O2 Heater element resistance is high
•Internal short or open in the heater element
•O2 heater circuit wiring high resistance
•open or short to ground in the wiring harness
Possible Solutions•Repair short or open or high resistance in wiring harness or harness connectors
•Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)

Mark (mhpautos)

Hi jimmywest,

Thank you for the donation.

P0135 = HO2S sensor circuit malfunction. Bank 1
P0155 = HO2S sensor circuit malfunction. Bank 2

Bank 1 is the one where cylinder is located.