PCM Diagnostics & Tuning - Pulled a few codes from a buddy's '99 Chevy van...

What exactly do they mean?

P0141 HO2S Heater Circuit Bank 1 Sensor 2 - (I know this is one of the o2 sensors, but exactly which one)?

P0171 Fuel Trim System Lean Bank 1 - (Not really sure what this one means)

P0174 Fuel Trim System Lean Bank 2 - (Not really sure what this one means either)

So i'm just assuming that those last 2 codes are tellin him he's running lean on both sides? and the first one is one of the o2 sensors, he has a stutter/hesitation, just tryin too help him troubleshoot it, thanks guys! :)

I think that means you should have to replace the sensors or check to make sure they are propertly connected. That should make the other two codes go away. What do you other guys think? I am no wizard.

It thows a lean trim is the trim value goes higher than +25% fuel trim.

Heated o2 Sensor Bank 1 side of the motor Oxygen sensor after cat is throwing a code.

Usually if both Fuel Trims are set at the same time its usually MAF.