A week ago, my CEL and VSC off lights came on and I pulled the code
and it said it was the bank 1 side 1 o2 sensor (thank you Club Lexus Forum!), so I replaced it with a Denso OE sensor 50 miles ago.

20 miles after I replaced it, I got a CEL p0134 error (no activity detected) and had it reset and it did not come back (yet), but now I get terrible mpg. I was getting 16+ around town - now only 13-14.

After installing the sensor - should I reset the ecu or something, or does it have to 'break in'? Is it possible I got a bad part?

Any suggestions would be appreciated, I don't want to burn up my cat by running too rich.

Thanks

 

The O2 sensor is a OEM Toyota or an aftermarket one? Sometimes the range of voltage given by the O2 sensors can vary and results in rich mixture (malfunction)...

 

Did you disconnect the battery and let it sit for a while?

 

Thanks for the replies.

I replaced it with a Denso, which from what I understand is the source for OEM Lexus sensors.

No, I didn't remove the battery cable. What would that do?

 

How does resetting the ECM resolve this? Isn't it 're-learning' now?

Also, what is the best way to reset it?

 

The computer should only take 10 minutes of driving or so before it has recomputed a correct map throughout the fuel curve and timing. These are not the old 8 bit computers on 80's Toyotas where things took long to adjust, these are complex fast calculating ECU's that perform things on the fly faster than we can diagnose by eye with tools.

If its taking longer than a full tank of gas for you to actually notice a decline in consumption economy, there is obviously something still very wrong. It may not be a crippling malfunction, but it will be worthwhile to visit a dealer or a specialist. These are complex matters of electronics and hundreds of sensors which might take an examination by a specialist to know from past defects on other cars and things prone on specific models.

I'm not trying to be unhelpful but sometimes a good eye by somebody who deals with these cars is all it takes to pinpoint a fault that's not recorded by the ECU and fix it.