Replacing 02 Sensors

[John]

I’ve got 310,000km (192,000 Miles) on a 2001 Ford Ranger 4.0L, 2WD, Auto. I’m told I have four, two before the cat, and two after the cat. When replacing oxygen sensors do I replace the one that is the problem (Bank 1 Sensor 1) or replace them all due to mileage & age?

Topic

[Coty Miller]

Depends… Normally the upstream ones go bad before the downstream ones because they are exposed to more heat… It’s fine to replace only what is bad, if you got cash to spare, it never hurt to replace the all… I always like to replace all of them just while i’m at…

[college man]

Start with the one that is the problem and go from there.

[Konrad]

An oxygen sensor can be bad and not throw a fault. Sometimes sensors will just go dead and you can check them with a volt meter. More commonly oxygen sensors will become slow due to age or contamination and will need to be checked with an oscilloscope. Slow sensors typically won’t throw a fault and will cause driveability issues.

Bosch ESI Tronic lists the useful life of an LSM11 4-wire sensor as more than 10,000 hours at less than 300 degrees C. Factoring in exhaust heat, the life span of a sensor is probably 100,000mi or so. Early sensors had a replacement interval of 60,000mi and some cars even came with a ‘lambda’ light to remind you to check the sensor.

http://rb-aa.bosch.com/boaa-sg/Product.jsp?prod_id=35&ccat_id=21&language=en-GB&publication=1

[Author]

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