Ok, I was driving my 08 vortex max on the highway the other day. It was relatively warm here in Fl and we were in a convoy. We averaged 80. But, when we hit the tolls, we were driving kinda spiritedly getting back up to speed. After several spirited acclerations, i then got into a cruise and my check engine light came on. Trucked seemed to run alright. A check of the codes when i got home revealed a P1174 error code. (P1174 indicates fuel trim cylinder balance malfunction. This means that your cylinder-to-cylinder air to fuel ratio is not balanced properly. Usually caused by a faulty heated oxygen sensor located on the exhaust or a simple vacuum leak. It will not harm your vehicle but it will lower your fuel mileage and the engine light will remain on until the issue is fixed.)

So, since my truck has over 70k miles, I figured (please let me know if I am way off here) that this may be a good time to replace the O2 sensors. Went to advance auto and got a great deal on a pair of sensors. However, when I went to replace them, I noticed my truck has 4 (yes, I said four) sensors and they are different. A pair is located pre and another pair is located post catalytic converter. The two i bought are before the cat (between the cat and exhaust manifold). Advance auto doesn't even show a part for the post cat. (autozone does, but of course advance auto doesn't offer that part number).

So, my question is which one is more likely causing the problem. I guess I could replace all four (what idiot thought that a truck needed four of these stupid things is beyond me) of the sensors. But, would rather not. I have looked online for a decent tutorial on how to test them, but have yet to find anything worth wild. Would rather not send it to the stealership.

Any advice would be greatly appreciated. Especially from someone that has run into this before.

Thanks Eric

 

In case of V8 engines, there are usually four oxygen sensors, front left, front right, rear of the engine (all are pre-cat) and one post-cat sensor. I would suggest you to replace the sensors from the auto parts shop, where you'll find exact fitment note for your 2008 Chevrolet Silverado 3500 HD Oxygen Sensor, so you won't have to worry about a wrong purchase.

 

the post cat 02's are for checking catalytic convertor function only.

make sure the fuel trim for the other bank isn't askew also.

any aftermarket air filter or intake on the truck?

 

It would be pre cat sensors. They judge of your truck is running lean or rich and adjust to it. If they go bad your truck will probably run lean and that's what made that code.

 

Ok, thanks guys. Well, I do not have any aftermarket stuff on my truck. Actually, the stealership sold it to me with aftermarket dual exhaust on it. It was so loud and obnoxious, the first place i went was to a muffler shop who promptly returned it to stock. the salesman told me he had sold my truck when it was new and the owner had put the dual exhaust on it.

So, since it has 71k miles on it, I went ahead and replaced the two sensor (pre cat), replaced the spark plugs (with OEM iridium plugs), upper intake manifold cleaner (courtesy of Sea foam), and did a brake job (Wagner extreme duty pads and Power slot cryo rotors). Going to Ocala tomorrow (2.5 hour driver on the interstate) and picking up my camper. When i hook up to the camper, I plan on putting two pints of sea foam into the gas tank and running it back home. Usually that trip uses about 3/4 of a tank. Will advise how it all works out