SES light, O2 Sensor(s)?

Yesterday morning the SES light came on and stayed on until the code was cleared at Autozone. Two codes came up, same number indicating faulty O2 sensor(s). The friendly Autozone clerk looked it up and found my 99 3.8 needs two O2 sensors, one upstream and one downstream. Is it a coincidence that both sensors failed at the same time? Could the code have been triggered because of the mileage on my car (201K+)? I'm not sure if I want to tackle replacing these sensors myself. Bosch replacements are listed at $73.98 downstream and $67.98 upstream. SES light did not come back on when driving home.

-Mike

Did you happen to get the code numbers? Its hard to confirm which sensor(s) are causing a problem without the code, sometimes the AZ guys are right, and lets face it, sometimes theyre not.

It is strange that both failed at the same time, and if they are original sensors, with that mileage, they had a good life.

How is your gas mileage? The upstream sensor is located in the rear exhaust manifold and has a pretty large effect on the amount of fuel you burn, therefore gas mileage.

The downstream sensor only monitors the catalytic converter, so depending on the code, it could actually be the converter thats the problem instead of the sensor, but the sensors go nuts someitmes too. But it has no affect on fueling. How is the car performing? Does the converter rattle if you smack it somewhat gently with something heavier?

Both arent too hard to change, but you might just wait and see if the codes come back. Im also surprised AZ cleared them, because the last time I went there they told me they couldnt clear it due to liability reasons.

By the way, Ive not heard many good reports from using Bosch o2 sensors with the 3.8, but thats just an opinion.

Thanks, LittleHoov.

I knew I should have written that code down, I think it was P0137, came up twice for bank 1 and bank 2.

The car is running fine, gas mileage hasn't dropped, still around 24-26 mpg.

No light this morning when started, think I will run it to see if the SES light returns.

-Mike

Im not entirely sure the Intrigue even has "banks", those codes are universal and the bank indication is for vehicles that have multiple catalytic converters, etc.

It should come back on after a few driving cycles if the problem is still there. But it could just be one of those weird things. I get a P0420 code from the rear sensor every like 3 months or something. Sometimes itll show up twice in the same week, then wont show up for several months. I think my aftermarket cat throws it a curve every once in a while.

I agree. There is no bank 2. P0137 relates to Bank 1, Sensor 2 (post CAT). 02 sensor circuit low volts.

FYI:

Since Autozone cleared the code almost two weeks ago, the SES light has not come back on and the car drives fine.

-Mike

indeed it was one of those funny problems that happen once, and never again. I wish all car troubles could work themselves out :grinyes:

First off, make sure that the AutoZone employee didn't just see the words "oxygen sensor" when he read the code definitions and assume that you need new oxygen sensors. This happens all the time, but what you need to remember is that many of the people that work there really don't know what the definitions mean or realize that there's more to a properly diagnosing a problem than just reading the codes.


First, the first 1000 Pxxxx codes are "generic" but they are generic because most are applicable to all vehicles. OEMs are allowed to set their own parameters which trigger the generic DTCs.

Second, the "bank" refers to what bank of cylinders in which the sensor is located. Bank 1 is the #1 cylinder side and Bank 2 is the opposite side. Sensor 1 is the pre-cat sensor, sensor 2 is the post-cat sensor. If both banks share the same sensor(s) then the code referring to Bank 1 is triggered.

I would check the fuses under the hood. IIRC there should be one labeled "HO2S" which is for the heater circuits on both oxygen sensors. If this is blown the sensors could be falling under their usable temp. (about 600*F) and not putting out an accurate reading causing the troublecodes you are seeing.