05 Silverado codes PO131 PO171 PO300

[joeelutz]

I've had trouble recently with my 05 Silverado 5.3L intermittently idling rough and running rough at low engine speeds. The check engine light came on and the exhaust smelled bad. I got the codes PO131, PO171, PO300 which suggest a lean condition on the left bank. However when I pulled the spark plugs, all the plugs on the left bank looked rich and the ones on the right looked normal. Well I disconnected the left front (pre-cat) O2 sensor and drove it today and it runs fine now although it does turn on the check engine light since the O2 sensor is disconnected. It appears that the O2 sensor was giving a false lean signal and the computer was over richening the left bank to try to compensate. So I'm going to install a new sensor tomorrow. I'm glad it wasn't a cracked intake.

I just thought this may help someone experiencing the same problems.