This happens on a car that I am looking at buying and want to know if it sounds like just the O2 sensor is failing, or if there are bigger problems...

He says when he is cruising at highway speeds 70+ mph the CEL comes on, and ONLY at these speeds does it come on, and it consitantly comes on at these speeds. He read the code as an O2 sensor code.

Does the O2 just need to be replaced or are there A/F or Ignition problems hidden behind this??

Thanks

Matt

 

There's a couple different O2 sensor codes, which is it? It could always be a wiring problem, whether the code is for the sensor itself or the heater.

 

Could be the O2 sensor. My CEL went on and stayed on, no sounds from the engine.

 

Its code 43 (fuel system) the car has had an engine swap and did this before and after the swap...now it has a B20B

 

I think 43 is the one that may have other problems behind it. It's not obviously a bad (or disconnected) sensor, that would be code 1. Or a bad sensor heater (41).

I think 43 is a catch-all, where MAP, TPS, injector time, O2 sensor, all compared against each other; something doesn't add up & the ECU can't pin it down to one single faulty sensor.