CEL is on

[CrystalShine]

Folks,

MY 2000 986S (50,000 miles) engine light is on. It happened 2 minutes after refueling at National Park. Could that be the fuel? Dirty stuff?

OBDII scan tool found the code P0115. After about 25 miles driving, CEL is gone by itself. I cleared the store data later.

The following day, after about 5 miles driving, CEL was on again.

Drove 380 miles and scan with OBDII, Found codes P0133 and P1275.

The car appear to drive fine. CEL solid (no blinking).

The tempature of the national park was very cold, 40 F.

Please help.

Edited November 7, 2005 by CrystalShine

[ar38070]

The manual says this is the front O2 sensor bank 1. That is the passenger side. I would swap the O2 sensors side to side and see if the problem moves with the sensor. If it does then replace.

[CrystalShine]

The manual says this is the front O2 sensor bank 1. That is the passenger side. I would swap the O2 sensors side to side and see if the problem moves with the sensor. If it does then replace.

Hi ar38070,

Can you tell me where is the O2 sensor location? any picture?

Thanks for helping out.

[ar38070]

Under the rear of the car. Locate the exhaust manifold, follow the pipes toward the muffler. Between the manifold and the exhaust are the catalytic convertors. On either side of the catalytic converter are the O2 sensors. Your code indicates the sensor between the exhaust manifold and the catalytic convertor is faulty. The O2 sensors are numbered 23 in the attached picture. The picture only shows two of the four O2 sensors that are present.

[CrystalShine]

Under the rear of the car. Locate the exhaust manifold, follow the pipes toward the muffler. Between the manifold and the exhaust are the catalytic convertors. On either side of the catalytic converter are the O2 sensors. Your code indicates the sensor between the exhaust manifold and the catalytic convertor is faulty. The O2 sensors are numbered 23 in the attached picture. The picture only shows two of the four O2 sensors that are present.

Thanks so much. Will try the swapping and see.

[ukchris]

Aren't P0133 and P1275 the same error code but for each bank, implying the same error from both sides? If so will swapping help? Is it likely they could all be bad at once or maybe another cause such as the MAF?

Chris, trying not to be too dangerous with very little knowledge!

:)

Edited November 8, 2005 by ukchris

[ar38070]

P0133 is "Aging of Oxygen Sensor Ahead of the Three way catalytic converter (cylinders 1 to 3)".

P1275 is "Aging of Oxygen Sensor Ahead of the Three way catalytic converter (cylinders 1 to 3)" - Below lower limit.

I interpret this as P0133 you have a sensor problem. P1275 by the way it seems to be reading low.

[CrystalShine]

P0133 is "Aging of Oxygen Sensor Ahead of the Three way catalytic converter (cylinders 1 to 3)".

P1275 is "Aging of Oxygen Sensor Ahead of the Three way catalytic converter (cylinders 1 to 3)" - Below lower limit.

I interpret this as P0133 you have a sensor problem. P1275 by the way it seems to be reading low.

BTW.......Which O2 sensor should I try, before or after the cat? I am guessing the one BEFORE, right?

[ar38070]

Yes the one between the exhaust manifold and the catalytic converter. You may also just want to check to see if the connector is loose first and/or that the connection is clean.

[PTEC]

Oxygen sensor ageing faults are the easiest CEL's to diagnose.

The DME keeps track of the reaction of the oxygen sensor. If you look at an oxygen sensor voltage over time on a graph you'll see the voltage fluctuating anywhere from .2 to .9 volts or somewhere around there. If the voltage doesnt fluctuate fast enough, the DME will set a fault. Slow reaction means the sensor is aged and not performing up to par. Toss a new sensor in.

Some people will try to "clean" the sensor using a torch and getting the probe tip red hot. I've never tried this so I dont know how good it works.