CEL on with this code.

[Crystal Shine]

Help!

2000 Boxster S 70000 miles with CEL on

OBD II found the following codes: P0139 and P0140

It said the Oxygen sensor on Bank I Sensor 2 is not working.

Questions: Where is it located? What should I do?

1500 miles ago I changed oxygen sensor on passenger side before the CAT with new OEM part.

Thanks!

Jacky

[Loren]

P0139 Ageing of Oxygen Sensor After TWC, Bank 1

P0140 Oxygen Sensor After TWC, Bank 1 – Open Circuit

P0139

Potential causes:

Implausible signal from oxygen sensor

– Oxygen sensor

P0140

Potential causes:

Open circuit in signal wire or ground wire of oxygen sensor.

Oxygen sensor heating not functioning.

– Wiring harness

– Oxygen sensor

– DME control module

Without seeing your O2 sensor voltages (before and after) it would appear that you have a wiring/connector problem at the sensor(s).

If the wiring looks and tests ok - then I would replace the O2 sensor before the cat first - clear the codes and see if the after cat O2 sensor r a code again.

[Crystal Shine]

P0139 Ageing of Oxygen Sensor After TWC, Bank 1

P0140 Oxygen Sensor After TWC, Bank 1 – Open Circuit

P0139

Potential causes:

Implausible signal from oxygen sensor

– Oxygen sensor

P0140

Potential causes:

Open circuit in signal wire or ground wire of oxygen sensor.

Oxygen sensor heating not functioning.

– Wiring harness

– Oxygen sensor

– DME control module

Without seeing your O2 sensor voltages (before and after) it would appear that you have a wiring/connector problem at the sensor(s).

If the wiring looks and tests ok - then I would replace the O2 sensor before the cat first - clear the codes and see if the after cat O2 sensor r a code again.

Hi Loren,

Oxygen sensor on the passenger side before the CAT was just replaced with NEW one oem 1,500 miles ago (2 months ago). Wiring looks ok. Is it time to buy new one for after the CAT on the passenger side?

[mikefocke]

I hope you are going to do this yourself.

Some sources for cheap parts and a DIY with pictures here

It is really trivial. Or at worst, have a muffler shop do it with the part you bought online. Don't pay the dealer just to replace the sensor. Only pay them if the swap doesn't cure the problem and you need further diagnosis.