02 Sensor MIL

Why don't you just replace the O2 sensor 1 as the code suggests. The code indicates a heater problem in the sensor. It is probably a little slow coming up to temperature. There were a lot of good answers in your other thread so why keep beating the bush and just replace the sensor. Also get a service manual. The code reader is useless if you don't follow the service procedures....

Because the chart of the O2 sensor with the MIL code shows that it is working properly (I think).

John

Actually, it shows the sensor activity but it shows nothing of how the heater is performing. You can either measure amperage thru the heater circuit, or, do whatever might be necessary to turn the heaters on with the engine cold and NOT running and then watch the O2 sensor voltage, it should change as the heater begins heating the O2 sensor element, this is one test where you could compare the output of a known good O2 sensor (sensor2) to the one you suspect as having a problem. Cold engine, key on, engine off, both )2 sensors should begin operating and have nearly identical voltages -if- the heaters are working, the one with a faulty heater will lag or stay at threshold voltage much longer than the one with a properly operating heater.

Thanks Neil for taking the time.

John

The ECM doesn't care about any of that data as far as the P0135 code is concerned, it only looks at the amp draw of the O2 sensor heater. It may work fine after the engine runs for a while, but if the heater is dead it may take too long to go into closed loop.