New O2 sensor lasted a week???

[Ardvaark]

I bought a oxygen sensor validated Bosch 15123 on that auction site. Spliced it in with crimp connectors and got better performance and gas mileage for a week. Now the 1221 check engine code has reared its ugly head again. I was so happy that I finally got the new one installed and it crapped out already? I'm at a loss gentlemen. This is sooo weird. I have no vacuum leaks and no other codes. HELP

[shogun]

1221 is an 02 code. this does not mean the 02 is bad. It means that it is out of parameters so something is causing the engine to be rich or lean. If you are sure the 02 is well connected, test it with a multimeter. Then it is time to start checking for things that could cause metering issues. I would start with the cheapest and most obvious and check for vacuum leaks, even if you did that before already.

I had the same issue on an E34, I spent a long time tracking down, was sure there were no vacuum leaks and replaced the 02. It ended up being that the throttle position sensor was way out of standard spec, so the car was adding more fuel thinking it was getting more throttle than it was. Get a multimeter and check voltage open and closed. all the specs are in the Bentley or workshop manual.

[Ardvaark]

It's so funny that you mentioned the tps. I just installed a new one a few days ago. I got it from the same place for 26 dollars. There is no writing on the part like the old one had. I replaced it because I have a little extra money and was trying to do some pm. I'm going to put the old one back in and see what happens. Thanks for your post because I never would have thought that it could be causing the problem.

[shogun]

Are you sure the O2 sensor you bought from that cheapo seller is original? Just some weeks ago one of my wrenching buddies wanted to install a cheap chinese made O2 sensor to replace the old Bosch one, as he had to go to inspection to get a new sticker. After we installed it, the engine ran like crap. Turned out that the cheap copy O2 sensor had an internal short. Then we installed the old Bosch sensor again and he went with that to the bi-annual inspection and passed the test.

Testing throttle position sensor from the German E34 forum copied, translate
Test Drosselklappenpotentiometer M50-Motoren :

Der Poti ist an der rechten Seite der Drosselklappe befestigt und lässt sich nicht einstellen. Die Motronik schickt ein Spannungssignal an das Poti und misst die zurückgegeben Spannung. Die Spannung wird kleiner wenn sich die Drosselklappe öffnet.

Test 1 :
- Stecker abziehen, - Zündung an, - Spannung am Stecker messen. Sollwert 5VDC (ungefähr)
Test 2 :
- Stecker abziehen, - Ohmmeter anschließen, - Drosselklappe öffnen und Werte messen : Pin 1 zu Pin 3 : ca. 4.0 KOhm , Pin 1 zu Pin 2 : ca. 1.0 bis 4.0 KOhm . Öffnet man jetzt langsam die Drosselklappe dann muss der Wert von 1.0 KOhm nach 4.0 KOhm (jeweils Anschlag zu Anschlag) sich ändern. Ist dies nicht der Fall, Poti tauschen. Poti lässt sich nicht einstellen.

so between pin 1 and 3 approx 4.0 kohm and pin 1 to 2 approx. 1.0 to 4.0 kohm. when you open the tps, then the value must move from 1.0 to 4.0 kohm = from end to end

[zubbie]

Many things can throw an O2 code. Intake air leaks, exhaust leaks, bad O2, plugged cat etc.

I generally don't buy grey market sensors or electrical parts. Had too many duds.

[Ardvaark]

Thanks for the responses. The o2 sensor came in a Bosch box but there was no writing on the body itself. The tps sensor just came in a plastic bag with no writing on it either. I sent a message to the seller yesterday and have not heard anything back yet. I'm thinking I just wasted a little over 50 bucks on fake or substandard sensors. Oh well you live and learn. I'll give the o2 sensor guy another email asking for a resolution. I measured the tps per the instructions and was getting 5 plus k . I figured it was just a new part that needed breaking in plus it was late and I was tired. My old tps measures like 4.5k from one to three. I'm going to put the old tps in right now and clear the codes and see what happens.

Thanks again!

[Ardvaark]

Well, other than the high idle, went down to 800 btw, the o2 sensor code hasn’t tripped yet. The tps guy is going to measure me out a new one on Monday. So that’s cool. Maybe the o2 sensor is okay. Crossing fingers.

[Ardvaark]

Ok, so the tps guy issued me a refund and a never heard back from the o2 sensor guy. 1221 is back this morning, my best guess at this point is to just spend the money on a real o2 sensor that was made for my car.

[Ardvaark]

So, feeling depressed and suicidal over this o2 sensor that has put me over the edge psychologically, I get into my car to run some errands and I noticed the check engine light is no longer illuminated. I'm thinking oh great, the light burned out from being on all the time, so I turn the car off to check and see if the light comes on while the key is in the run position, it does! Light is not burned out. I guess whatever was wrong cleared itself. I'm happy once again and no longer suicidal. Hopefully it doesn't come back on any time soon but I'll assume it will at some point. I'm really mostly happy with this car and wouldn't trade it for anything. And with it's ultra low mileage I expect to keep it as my daily for at least another 10 to 15 years.