OK, guys, I did a search for specific codes but so many people trying to be helpful have posted the ENTIRE list of OBD2 codes for the c5 every freakin' thread pops up. So please don't post the code list, I already know what they are.
So here's the deal, the car runs well for the most part. I occasionally have a dip in engine speed at idle, down to around 500-600 for a few seconds, then it comes right back up.
Anyway, every so often it will throw the CEL and codes P0140 Circuit Insufficient Activity Bank 1 Sensor 2, P0161 Heater Performance Bank 2 Sensor 2, and P1416 Secondary Air Injection System Bank 2.
I think I get that I have a problem with the air injection and I know it's not an uncommon problem, especially the check valve, but I'm a bit confused with the Bank 1/Bank 2 issue. Are banks 1 and 2 on the same circuit? I'm assuming banks 1 and 2 are left and right engine side. Am I wrong about that?
Anybody else run into this? Thoughts?

 

I think that Bank 1 is the driver's side of the engine and of course, Bank 2 is the passenger side. Don't hold me to it but it appears to be the case from all the posts here I've been able to figure out.

 

Bank 1 is drivers side, bank 2 is passenger side.

 

Cool and Thanks

 

P1416---- this is for the smog air pump --it is located under the drivers side headlight area----Most common issue to trip this code is carbon filled or plugged up secondary check valve---in your case the pass. side check valve----use this site and it goes thru diagnostics and repair to correct:
http://www.gearchatter.com/viewtopic9447.php

P0140 & P0161 are for the REAR 02 sensors--One for the driver's side and one for the pass side
Again here are the links from gearchatter to do diag. and repair
http://www.gearchatter.com/viewpost14541.php
http://www.gearchatter.com/viewtopic10710.php

Although the codes for the rear 02's are for different reasons--They still indicate that something is going on back there---
BACKGROUND----
ONLY the FRONT 02's are used for fueling your engine--They are the most important 02's--without them working your car goes into a power reduction "limp mode"
THE REAR 02's are ONLY used to report the "condition of your cats" period !!!
SO---these rear 02 codes can be telling you that:
1. both the sensors have failed and need replacement (cannot be cleaned)
2. The condition of your cats are BAD !! and need replacement
*really depends on how many miles your car has
*how well it's been maintained
oil change--religious injector cleaner--oil and fuel filters etc.
* constant use of bad gas

Combining the p1416 ( which is usually a carbon fouled check valve ( these can be cleaned sometimes) with the possibility of failed rear 02's or plugged cats-- to me points to a common sourse for all the codes---A carboned up dirty exhaust system.
Remember that the secondary air pump system pumps fresh Oxygen into your exhaust

Hope this helps---all of these are very Common codes even sometimes on well maintained cars--but cheap bad gas really fouls things up--I use my car traveling a lot and get gas from unknown stations and both my check valves failed and had to be replaced--
GEARCHATTER is the best DTC code and diagnostic site I've ever found--uses plain understandable language for repairs but also includes the technical stuff for those with test equipt.

 

Thanks tblu, and others. I will admit that we are guilty of using gas from some questionable sources sometimes, especially lately when prices were hovering at or over $4/gallon. Of course, the car also has over 80k miles on it so it's also possible it's just that time. I cleared the codes yesterday and have driven it about 60 miles since and they have not recurred, but it seems like I do this every few weeks. Only a matter of time.

 

I recently had the CEL set for code P1416, the first time I've experienced a CEL on this car. ('01 C-5). I did a search here, and one of the "fixes" for this condition was to disconnect the AIR hose at the junction adjacent to the alternator (big rubber hose at/under the alternator), and spray a good dose of mass airflow sensor cleaner into the hose, then take the car for a spirited ride. This pulls the cleaner through the AIR check valve, freeing it up.

I did this, and I've been OK since...



(Thanks to Bill Curlee for the post on this)