chamilka

Hi All
I got following Diametric error code: P0140:O2 sensor behind cat. conv. Cylinder (4-6)

I replaced the O2 sensor at the driver side, the one that attached to the exhaust pipe coming out of the Cat. In other words: the sensor located between the Cat and Muffler at the driver side. I still get the error and wonder “behind” means ahead not after?
Does “behind cat” means after Cat or before ?
Thanks all

Macster

You got the wrong bank. The error code references the #2 sensor of bank #1.

The #2 sensor is located after the converter, downstream of the converter, further away from the engine than the #1 sensor.

The #1 sensor is located in the exhaust header just ahead -- upstream -- of the converter, closer to the engine than the #2 sensor.

IOWs you got the right sensor (#2 after the converter) but the wrong bank.

chamilka

Macster - Thank you so much for the inor,So some reson I thought 1-4 was driver side? so all I have to do is repeat the same on the other side - got it . thanks again

Macster

Yes, do to the other side what you did to the first side.

BTW, unless a sensor fails shortly after installation I prefer to replace sensors in pairs, at least, and really if the miles are real big to replace all 4 sensors.

My concern is one has two sensors both with the same miles on them. One acts up and is replaced. The other though still has the miles and while not acting up could result in a difference in how the two banks are fueled because due to its miles has a slower response time to changing oxygen level in the exhaust gases.

In fact in January of 2015 and within the last month or two I had all 4 sensors replaced in my Turbo (at 132K miles) and in my Boxster (at 300K miles).

In the case of both cars just one sensor tripped the CEL but I decided that due to the miles and the importance of balance in the fueling of the two cylinder banks to have all 4 sensors replaced.

chamilka

Good point, thank you again for the infor and recommendations. really appreciate it.

chamilka

Macster- I am reading another post where you had commented on the same topic. I want to clarify something: per that post and the diagram it says "For the Boxster/Cayman cars this would make the #1 cylinder the cylinder immediately behind the passenger (USA cars, left hand drive)"

so in this light would't Cylinder (4-6) be the driver side?

here is the link to that post:
https://rennlist.com/forums/boxster-...er-layout.html

Macster

Yes, that info is from the Bosch Automotive Handbook and cylinders 4, 5, and 6 are on the driver's side of the engine.

This assumes Porsche follows the Bosch handbook in this regard and I believe it does. I have not come upon anything that suggests it doesn't.

BTW, if you have the Bentley Boxster manual on page 02-6 at the bottom of the page there's a drawing of the engine's cooling system. The passenger side of the engine has the cyinder positions numbered 1, 2, and 3. The driver's side has the cyinder positions numbered 4, 5, and 6. To determine the front of the engine looks at items 1 (water pump) and 3 (T-stat).

chamilka

Thanks man, replaced the other side as you suggested and so far no o2 sensor error
thanks agina for our help