What is diagnosis for 2001 Chevy Silverado System Lean Error code?

Question

A friend just replaced both knock sensors on my 01 Silverado V8 4.8. my original error code for knock sensor is gone... But new error codes P171 & 174 Lean System Codes emerged with my chrck engine light back on. These error codes werent present before... Any ideas to why these new errors are occurring. Truck has a sputtering feel when idle... No issues when driving.

Answer 1

The problem is the upper intake plenum gasket.given the fact that you didn't have this problem before, either because the gasket was disturbed and now not sealing properly or the gasket moved during installation (not likely) either way the gasket needs to be replaced.

You didn't state if your friend replaced this gasket when removing the upper plenum to replace the knock sensors.If he didn't ..original gasket will be the orange type .

GM has a new TEAL type gasket (new and improved) LOL... replace with this type gasket (from dealer only)

This will resolve your issue...

Answer 2

Look for air leaking around the intake air hoses or around the intake manifold, under the throttle body etc. The O2 sensors aren't bad (there's 2. 1 before the cat and 1 after) or you wouldn't be getting this code. Most of the time a lean code comes from an air leak, mis-firing injector, or vacuum leak. If its lean on both banks I'd look for an air leak. Squirt some carb cleaner around all the connections and see if the idle changes. Where ever you notice the change, that's where its leaking. Make sure all the hoses are connected properly and you have no vacuum hoses disconnected. If that doesn't cure the problem, you may have a bad injector. You need an O' scope to properly diagnose those. Good Luck

Answer 3

Sounds like a o2 sensor is no good.