2001 Silverado 02 sensor

[Wormdrowner]

Check engine light has been on for quite some time, friend of mine checked codes with a hand held. The code said it was the 02 sensor behind converter, bought sensor from dealer...light still on. I brought to dealer for another problem and had them put it on computer, they also said it appeared to be the sensor. They tried moving it to the other banks and said the code followed that sensor. Replaced again...same thing, they said it wouldn't cause and harm and okay to drive. My son recently bought the truck and decided to try again....dealer claimed all 02 sensors were bad and replaced all four. Truck sounded a lot better and had more pep after replacement of sensors. Well...that lasted for one day and the light is back on. Dealer said they would look at again to see what they could find...anyone else had this problem? Would a converter be causing this, it also has after market exaust if that might be an issue. Have a hard time believing that all sensors would have been bad. Truck has 125,000 on it.

thanks

[Snowking]

if all sensors where bad you would have 4 codes. i do beleive you can test them with an omh meter

[Jeremy airjer W]

what was the specific code?

As far as ohm checking it dependsw on what the problem is with the sensor. If its open than an ohm check would reveal the open circuit. If it was stuck or lazy an ohm check may not identify the problem.

[Wormdrowner]

Don't know the specific code, would they have put that on the work order. Could all four sensors be bad? If the check engine light came on again what else could possibly cause this?

[Jeremy airjer W]

They might have? It will be a P followed by four numbers. P0171 for example. It all depends on what codes where present. They could be lean codes, Rich codes, low voltage, high voltage, upstream, downstream, heater circuit, cat inefficiency, bank 1 and bank 2 to name a few. These are all clues and based on the facts that are gathered a reasonable deduction can be made.

For example if I see lean both banks my first thought is vacuum leak. If I see lean one bank I would be more suspicious of the O2.

There are codes that can come up that don't implicate O2 sensors that can be a result of bad O2 sensors. For example last week I had a tahoe with a code for fuel trim rich bank 2 and random cylinder misfires. After checking the misfire history they where all on 2,4,6,&8 cylinders. The fuel trims where also maxed for bank 2. The bank 2 O2 was lean all the time. Unplugged that O2 sensor and everything goes back to normal. The O2 was in fact stuck lean and a new one fixed the problem.