Stefan Richter

While driving home, my CEL lit up. I took it to a local guy to have the code read, and it came back with oxygen sensor no 1 bank 1 no signal. Although I have a reman with only 30K, I suspect O2 sensors are original to the car and have 111K.

Can I just replace the one sensor (if so, which one of the four is it), or should I replace them in pairs, or all 4?

Thanks in advance.

Stefan

Dharn55

Sensors are in the exhaust system and so would not necessarily have been replaced with engine. You can replace just one sensor. Not sure exactly which one that code is. Bank one is the left/drivers side. There are two on each side, one before the cat and one after the cat. What year is your car?

Stefan Richter

I know the reman came with new headers, but probably not the sensors. The patient is a 2000C2

Stefan

Loren

Your O2 sensors are on the cats 1 before and 1 after each cat (4 total). So they would not be changed with the engine.
Get a scan tool and find out which O2 sensor is bad and replace it.

67FJ45

Bank 1 Sensor 1 is before the cat, driver's side. Yes, you can replace just the failed sensor, but life expectancy is about 100k miles for a well-maintained, heated sensor (what is on your car), so you can expect to replace others soon if they have already 111k on them.

Macster

If you determine the O2 sensor needs replacing my advice is to replace both sides, both #1 sensors on banks 1 and 2.

Save the old sensor that is still working. Bag it and put it in a box the new sensor came out of. Handle both the old sensors and new sensors very carefully. They are suprisingly sensitive and delicate in spite of the harsh environment in which they reside and work, and do not take kindly to having the tip touched or being zapped with static electricity. Do not use ohm meter to check sensor either.

If you replace one 100K sensor with a new one and leave the other sensor in service there can be difference in adaptation between cylinder banks due to the difference in performance of the new and the old sensor.

Thus you should consider replacing O2 sensors in pairs.

Sincerely,

Macster.

Stefan Richter

I replaced both pre-cat O2 sensors on the car this weekend (along with a new air filter). The CEL immediately went out on start up and all appears well. My question now is whether the computer will store the code, or erase it automatically? The car needs to be inspected next month and I think an O2 sensor code might make it fail. I also remember that if you erase all codes, you need to put x number of miles on the car before an emission inspection can be performed.

Any insight is appreciated.

Stefan

springgeyser

-erase the code
-drive at least 100 miles

Macster

Poor man's technique is to disconnect battery. Follow all cautions and safety rules in doing this. Note radio and other security codes before you disconnect the battery.

Disconnecting battery -- a few minutes (15 or so is probably over kill but better safe than sorry) -- will erase any stored codes and reset long term fuel trims back to their defaults along with some other learned info. Readiness monitors are set to incomplete as well.

If you have a smog check/inspection coming up drive the car from cold letting it idle a couple of minutes, then drive at moderate speeds, but mixed driving (city, highway) for around 30 minutes or so. More is better.

Check with your state. In some the car is allowed to have 1 or even 2 readiness monitors set to incomplete and it can still pass emissions.

Tech at smog station where I took my car a year ago used small special code reader to check for any error codes and to ensure the readiness codes set to complete before he started. But he told me car is allowed two. (This in CA.)

Sincerely,

Macster.