2001 O2 Sensor Problem

[bruceb58]

Hi,

2001 IS300.

Have a "Check Engine Light" and pulled code p0161. This is a problem with the heater circuit on the rear oxygen sensor. Repalced the sensor with a new Denso sensor and still get the same code.

Any suggestions on what to do next?

Thanks
Bruce

[digger08]

CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.
The heated oxygen sensor (bank 1, 2 sensor 1) has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust gas and provide the ECM with feedback to control the air-fuel ratio.
When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the heated oxygen sensor informs the ECM of the LEAN condition (small electromotive force: < 0.45 V ).
When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio the oxygen concentration in the exhaust gas is reduced and the heated oxygen sensor informs the ECM of the RICH condition (large electromotive force: > 0.45 V ). The ECM judges by the electromotive force from the heated oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if malfunction of the heated oxygen sensor causes output of abnormal electromotive force, the ECM is unable to perform accurate air-fuel ratio control.
The heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low) current flows to the heater to heat the sensor for accurate oxygen concentration detection.

I would try some simple things first.

Clean the MAF sensor, check the intake area - are you drawing too much or insufficient air/ or even hot air into the air box. Do you have a short ram installed?

Did you reset the electrical system after the O2 sensor replacement?

Just guessing though

Digger08