So I failed my inspection today. One code popped up which was P0156. I believe a o2 sensor malfunction?
I drive a 1996 audi a4 2.8 quattro. Can someone explain this code to me please I have about 30 days to get it fixed. =(

 

On a normal OBD II car a P0156 code refers to the Bank 2,2 o2 sensor or the downstream (post-cat) o2 sensor on Bank 2 , I'm going to assume its the same code for an Audi. The O2 Sensor is a four wire sensor. The PCM supplies a ground circuit and a reference voltage circuit of about 0.5 volts. Also for the o2 sensor heater element there is a battery voltage supply wire and another ground circuit for that. The o2 sensor heater allows the o2 sensor to warm up faster, thus achieving closed loop in less time than it would normally take for the exhaust to warm the sensor up to operating temperature. The O2 sensor varies the supplied reference voltage based on oxygen content in the exhaust. It is capable of varying from about 0.1 to 0.9 volts, 0.1 V indicating lean exhaust and 0.9 V indicating rich exhaust. This P0156 code indicates that the Bank 2, 2 o2 sensor is stuck low for too long or isn\'t active at all.