Correcting Toyota Air Fuel Response

Feb. 27, 2023

This bulletin applies to 2008-2010 Toyota Highlander vehicles. Some vehicles may have a MIL on with DTC P0138 and/or P0158 (oxygen sensor circuit high voltage bank one or two). In some instances, a P2195 or P2197 (A/F sensor signal stuck lean) may also be present.

This bulletin applies to 2008-2010 Toyota Highlander vehicles. Some vehicles may have a MIL on with DTC P0138 and/or P0158 (oxygen sensor circuit high voltage bank one or two). In some instances, a P2195 or P2197 (A/F sensor signal stuck lean) may also be present. This condition is caused by incorrect air fuel ratio sensor response. Additionally, a P0606 (ECM/PCM processor) DTC may be present due to incorrect O2 sensor operation.

1. If DTCs other than P0138 or P0158 are present, go to Step three. If not go to Step two.

2. Check the A/F and O2 sensor values for the appropriate bank DTC freeze frame data. If the SFS voltage B#S1 = 3.35-3.70V and the O2S B#S2 = 0.70-0.90V, replace the appropriate bank air fuel ration sensor only (not the O2 sensor) to correct the P1038 or P0158 DTC. If voltage is not as mentioned, inspect the O2 B#S2 circuit for open, short or high resistance.

3. Inspect the air fuel ratio sensor for the appropriate bank. If the air fuel ratio sensor has an open or short on the A1A+ or A1A- wires, repair the harness and revaluate sensor operation. Confirm that the previous DTC do not reset. If no open or short is found, replace the applicable bank air fuel ratio sensor only to correct the P2195/P0138 or P2197/P0158 DTC condition.

4. Inspect O2 sensor two freeze frame data values. If the O2S B#S2 voltage is more than 1.10v and/or the O2S impedance B#S2 is more than 300 ohms when the engine is at normal operating temperature, inspect the O2 B#S2 circuit for open, short of high resistance. If no harness issues are found, replace the appropriate bank O2 sensor only to correct the P0606 DTC. If no open/short/high resistance is found, follow the repair manual diagnostic procedure for P0138/P0158.

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