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Old 09-01-2005, 04:41 PM
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Moneypit SEL Moneypit SEL is offline
Now what?
Join Date: Jun 2005
Location: SE PA
Posts: 525
Originally Posted by Mar10K
Not that I'm surprised - but I got a Check Engine light in the middle of a highway trip. The good thing is it's a different one than I've gotten before:

P0133 - Sensor Circuit Slow Response (Bank 1 Sensor 1)

I guess that means I have an old O2 sensor. I've reset the DTC to see if I get the same code again, since the O2 sensor seems to be responding when I pull up the reading on a graph. I'm a bit surprised it's this one, since the Bank 1 Sensor 2 reading does not change much, and I would have thought it was the bad one.

Do these things just get old and have to be replaced? 1987 MB has 90k miles.
The second O2 sensor is used to monitor converter efficiency. When all is well with the system, the front sensors will swing rich/lean in response to the fuel delivery, and the second sensors will meander about showing constantly lean. When the second sensor pattern starts to look like the front sensor, then the converter is no longer doing its job.
1989 300 SEL that mostly works, but needs TLC
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