If it was a leak, wouldn't it show up if you block the exit of the exhaust?

 

I'm not entirely sure the cause is an exhaust leak, but it makes sense. This code has also been know to be caused by vacuum leaks, but what could be leaking that only affects bank 2?

 

I think it's control. Not a leak. Do the paperclip trick.

 

You mean check the wiring for problems? Wouldn't the readings from the O2 be intermittent if there was a problem?

 

If the o2 sensor or an exhaust leak were the cause of your lean code it would be running rich while still setting a false lean code. So it should be dumping in a whole bunch of extra fuel. Are you experiencing rich running symptoms? A raw fuel smell from the exhaust, black smoke etc?

I'd still lean towards a vacuum leak. Monitor the short and long term fuel trim for bank 2 while spraying either carb cleaner or using one of those small propane bottles near the passenger side(bank 2) of the intake near the gaskets and other fittings. If you spray in one area and the short term fuel trims move towards zero significantly you've found the source of your leak. Keep in mind the fuel trims aren't instant, it might be delayed a second or two.

 

NO.

They could merely be sluggish or hover near one end of the readings.

Let me ask you something. You say the O2s both swing like they should and yet one bank is severely lean compared to the other. Yes?

Does the control stay in closed loop the entire time or does it jump back and forth from closed to open and back again?

What happens when you force it into open loop?

 

Bank 2 is running near the edge of actually setting a code for the lean condition, I wouldn't call it severe, just enough to set the code.
I have no indication of a problem other than the code, no performance issues, no black exhaust.

I've only scanned it during closed loop(I think) with the engine up to temp. How would one know if the PCM is switching back and forth? Also how would one force open loop? Unplug the MAF?

 

A scanner such as those from Snap-on indicate when you go in and out of closed loop. As that is all I use, I can't speak for others. I did have a wiring issue on my OBDI and it would go in and out of closed loop.

To force it into open loop all the time, merely unplug one of the front O2s. It will set a code eventually but it will put into open loop control. It would be interesting to see what the O2s see once it is in open loop. Even though the PCM ignores their readings.

 

Are the air pump check valves closing all the way?

 

That's an easy one to spot..the rubber/plastic tubes attached to it melt away if they don't......

 

I haven't had time to troublshoot further, however, I have checked the AIR valves to ensure one way operation, and they are good.