My 2000 millenia is showing a code P1173 Feedback A/F mixture Control (HO2S21)! When I bought it the from the dealer, the mechanic told me he replaced 3 O2 sensors and seemed to think that it might have a ground problem and didnt have time to fix it! Is this posible and where can i start to solve this problem? Any help would be greatly appreciated!

 

Which sensors were replaced. The P1173 is indicating a non-switching condition detected with the left bank upstream oxygen sensor. This is the one that is in the upper part of the exhaust manifold on the radiator side. The conditions needed to set this code are as follows. Input voltage to the PCM from this sensor remains ABOVE or BELOW .45 volts for over 32 seconds when engine speed is above 1500 and coolant temp is greater that 176'F. Normal operation of the sensor would be cycling between 0 and 1.0 volts about once or twice per second. Sensor would be suspect first if it is even plugged in but an overly rich or lean condition could also cause the same problem. Why was the mech throwing O2 sensors at the car in the first place? If they eagerly sold it to you in that condition knowing that there was this problem then they should be equally as eager to fix it for you.

 

Thanks for your help! Im not to sure how to go about fixing this problem other than to replace the sensor but I hate just replacing parts until I have actually tested the sensor! It appears to be pluged in and I will let you know something. Thanks again!

 

It is always belt to test the sensor operation before just replacing as that is not always the problem. If you will follow the wires off of that O2 sensor up to the back side of the intake plenum to the connector you will want to monitor the voltage at the Yellow wire. That is thte signal wire to the PCM. Should be cycling between 100 and 900 milivolts about 1-2 times per second within 1 minute after start up and rpms at 1500 or so.

 

Hey thanks for the info! Before I got your last reply I checked to see if it was connected and pulled and tugged on the wireing harness and the light went out on its own, but came back on after driving about 15 miles. Then I got to messing around with the hot wire for my stereo amp and I lost connection to the hot side of the battery by accident and the light has not came on for about 50 miles yet. Im going to tear into the wireing harness this weekend and try measureing the voltage. Is it possible to put the wrong sensor in it? It sounds to me that it takes 2 different kinds. Is that right? I have noticed a slight hesitation especially when its cold, and rear intercooler looks extremely dirty and i was going to clean it. Im also having trouble finding struts for the car. the ones I have found so far are $180 each. OUCHHHHHH!

 

The car made it 110 miles before the light came back on, and seems to run better with the light on! The upstream O2 sensor is cycleing between 0.09 to 0.78 volts at idle, and 0.13 to 0.73 volts at 2000 rpms. I have checked the connections and everything appears to be ok. One thing that I noticed is that the upstream O2 sensor is the same as the downstream sensors, which are the universal bousch part # 15730. What can I do now to fix it? Everything appears to be hooked up from what I can tell and doesnt seem to have a vacum leak. I was aslo still wondering where I can get a good deal on struts and need a repair manual for the car. My local Autozone doesnt have a repair manual. I would like to change the spark plugs, drive belt, timeing belts, and adjust the valves if they are adjustable. Any help you can give would be greatly appreciated!

 

Help!

 

try the egr booster

 

Since I grounded the exhaust the car hasn't had a P1173 code, but it has other problems