Oxygen sensor function

[danalyse]

Hard to say why my car is running again after is slowly deteriorated and would not stay running at all after starting. Cleaned the AFM replaced the accordian boot. Took out the fuel pump but didn't replace. Made sure all hose connections were tight. Running now with only with a very slight roughness. The OBD says 1222. My Peake diagnostic tool says oxygen sensor. Pulled a plug and half of the plug looks OK but the other side has some granular looking deposits. Question: does the sensor supply information only or does it tell the computer to alter the mixture.

[BMW_325i]

Straight from le Bentley manual:

The oxygen sensor monitors engine combustion efficiency by measuring the oxygen content of the exhaust gasses. That information in turn is used to control the fuel injection system and reduce exhaust emissions. Any problems with the oxygen sensor will directly affect exhaust emissions and the way the engine runs.


The oxygen sensor adapts the air/fuel mixture by sending a varying voltage signal to the fuel injection control u nit. The sensor is positioned in the exhaust stream and actually measures the amount of oxygen in the exhaust gas so that the fuel injection system can correctly adjust the air/fuel m ixture. A high concentration of oxygen in the exhaust gas indicates a lean mixture and a low content indicates a rich mixture. Thus, the signal from the oxygen sensor plays a major role in engine performance and driveability.

A worn out oxygen sensor will cause poor idle characteristics and higher than normal fuel consumption.

NOTE - The signal from the oxygen sensor is ignored by the fuel injection coritrol unit until the engine reaches a specified temperature. Therefore, when troubleshooting cold engine driveability problems, the oxygen sensor can be ruled out as a possible cause.

[jlevie]

A 1222 code is a Lambda fault. That could be a bad O2 sensor or anything else that upsets the A/F ratio (intake leaks, fuel delivery, AFM). The O2 sensor is a scheduled maintenance item with a replacement interval of 100k. If that applies, replace the sensor and then have a smoke test run to check for intake leaks.