My check engine light keep coming back on after my husband clears it. It states it is the upsteam O2 sensor. The car runs fine. It only comes on when I use the air but it doesnt happen every time it happened 3 times so far. Any Ideas why this is happening and why the car still is running fine?
Upstream O2 sensor Check Engine Light Error
- Thread starter DESLGRL
- Start date
andreigbs
Veteran Member
The CEL coming on after being cleared indicates (at least to me) that the O2 sensor is faulty. Perhaps your husband should look into further diagnosing the sensor and see if it requires replacing. That should resolve the recurring CEL.
oilhammer
Certified Volkswagen Nut & Vendor
The MIL coming on for a seemingly endless variety of issues on post-fix TDIs has become pretty common now. The dealer techs must just LOVE the warranty on these. I've had two already today. 
Good luck. You'll get to know the dealer service writers on a first name basis. After a while you'll realize why so many people delete the stuff. It sucks, but I didn't make the rules, I didn't try and cheat them, and I certainly would not have administered the nonsense that has become of it.
Good luck. You'll get to know the dealer service writers on a first name basis. After a while you'll realize why so many people delete the stuff. It sucks, but I didn't make the rules, I didn't try and cheat them, and I certainly would not have administered the nonsense that has become of it.
I would take it back to dealer but the dealer had me sign a document stating that there was no warrenty on check engine light codes. Lucky me!The MIL coming on for a seemingly endless variety of issues on post-fix TDIs has become pretty common now. The dealer techs must just LOVE the warranty on these. I've had two already today.
Good luck. You'll get to know the dealer service writers on a first name basis. After a while you'll realize why so many people delete the stuff. It sucks, but I didn't make the rules, I didn't try and cheat them, and I certainly would not have administered the nonsense that has become of it.
The reader we have to clear the codes is an old reader and doesn't give us VCDS txt file so we are going to buy a better one. Once we get the better one we will give you the information.
This vehicle has the emissions modifications completed?I would take it back to dealer but the dealer had me sign a document stating that there was no warrenty on check engine light codes. Lucky me!
You purchased this vehicle from a Volkswagen dealer?
No, I bought it from a used car dealership.
prsa01
Veteran Member
Are you saying the used car dealer had you sign the doc or a vw dealer? If the fix has been done you should have the extended vw emissions warranty regardless of anything you signed with the used car lot. If it hasn't been done MOST are eligible to have it done and then have the warranty.
Unless some "aftermarket" emissions work has been done by a previous owner, in which case you can disregard.
You can put your Vin in here if you want to know status: https://www.vwdieselinfo.com/
Unless some "aftermarket" emissions work has been done by a previous owner, in which case you can disregard.
You can put your Vin in here if you want to know status: https://www.vwdieselinfo.com/
PRY4SNO
Veteran Member
^^^ This.
tjg
Veteran Member
So about 8 months ago I kept getting a CEL for a primary 02 sensor "upper limit exceeded"
The dealership replaced the sensor twice and still the same code would show up.
On a (seemingly) unrelated note, I would fairly often get a flat spot in acceleration when I would hit 2nd gear after leaving the driveway from a cold start.
Well one day I went to start the car and it died after about 2 seconds of running and took some attempts to get going.
We hypothesized that the lifter pump might be going bad, but it turns out the ECU was failing. The tech said it failed a number of the tests they ran. I had the ECU replaced and haven't had either issue since.
I'll add, that I've also stopped using the fuel station I had been during that time as well... So the 02 sensor code could be from that too
The dealership replaced the sensor twice and still the same code would show up.
On a (seemingly) unrelated note, I would fairly often get a flat spot in acceleration when I would hit 2nd gear after leaving the driveway from a cold start.
Well one day I went to start the car and it died after about 2 seconds of running and took some attempts to get going.
We hypothesized that the lifter pump might be going bad, but it turns out the ECU was failing. The tech said it failed a number of the tests they ran. I had the ECU replaced and haven't had either issue since.
I'll add, that I've also stopped using the fuel station I had been during that time as well... So the 02 sensor code could be from that too