2007 running rich on bank 2

I have an issue with my 2007. When it's under 70 degrees outside, I'll get a rich on bank 2 code. But ONLY when I just let off the gas to coast down a hill or at idle. No CEL usually, just the stabilitrak light. It always goes back off after a few seconds. It never lasts. If it's warmer outside I'll never get the code. I've replaced all injectors with AC Delco on bank 2. It seemed to have helped it not be so frequent.

So if I have it under load going up a hill, once I peak the hill and coast down, the stabilitrak light comes on and it's that code. Once it's been about 30 seconds or I put it under load again it goes aways. Only when it's around 70 degrees or lower outside. Also, once the truck gets really warmed up after driving a good 15 minutes or more, it stops doing this. I really don't think it's actually rich either. It's really annoying because it makes the truck shift hard. Could this be an 02 sensor? There are literally no other codes that come along with this either. No 02 codes, but I've heard they can do this sort of thing without being bad enough to throw a code.

I would suspect a vacuum leak. Vacuum is much higher with low throttle or when idling, and that can suck in unmetered air. You could look at your short-term fuel trims at idle, then again at 2000 rpm to see if there is much of a difference.

Visual inspection might show a vacuum hose or connection that is compromised.

It might also be good to see if your upstream O2 sensors are working properly; that's easiest to see with a graphing scan tool.

what's the code? and what's the date showing while it's happening? even a cheap scanner should show you the fuel trims while it's happening.

when you decel like that, it should be in decel fuel cut, injectors closed and o2 sensors read dead lean.


do you have any broken off exhaust manifold bolts on that side? it's very common to pop a few over time.

j91z28d1 said:

what's the code? and what's the date showing while it's happening? even a cheap scanner should show you the fuel trims while it's happening.

when you decel like that, it should be in decel fuel cut, injectors closed and o2 sensors read dead lean.


do you have any broken off exhaust manifold bolts on that side? it's very common to pop a few over time.

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I have an hp tuner but I still am learning how to read things. I can get a read of me going down the road. Funny thing is, I have a broken exhaust manifold bolt on the bank one side. It's never given any issues before though. It's the very back one. I replaced my pcv hose a few months ago because it was cracked.

The code is P0175. It's strange because it won't do it for weeks and then it'll do it every couple days for about a week then go away again.

Fless said:

I would suspect a vacuum leak. Vacuum is much higher with low throttle or when idling, and that can suck in unmetered air. You could look at your short-term fuel trims at idle, then again at 2000 rpm to see if there is much of a difference.

Visual inspection might show a vacuum hose or connection that is compromised.

It might also be good to see if your upstream O2 sensors are working properly; that's easiest to see with a graphing scan tool.

Click to expand...

Wouldn't a vacuum leak make it run lean?

with hp tuners you can setup logging for the o2 sensors on both side and all then fuel trims, also should be a flag for dfc. give you something to compare, also I believe hp will show the freeze frame data from when the code will set. but you'll have to Google to make sure. if so, it will gave you a snap shot of what all is going on when it sets.

03GMCYukonXL said:

Wouldn't a vacuum leak make it run lean?

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Only in Open Loop.
In Closed Loop, the O2 sensors would notice that the MAF is consistently lean.
The constant enrichments could be big enough to significantly change the LTFTs,
yet not quite big enough to cross the trouble code threshold.

Marky Dissod said:

Only in Open Loop.
In Closed Loop, the O2 sensors would notice that the MAF is consistently lean.
The constant enrichments could be big enough to significantly change the LTFTs,
yet not quite big enough to cross the trouble code threshold.

Click to expand...

Aside from the PCV hose, where else could there be a vacuum leak. I don't really see any other spots aside form the EGR pipe and that doesn't seem to be leaking at all.

In theory, anywhere between the MAF & the O2s. In your case, it's passenger side.
If you don't find anything with your eyeballs, it's likely the intake manifold.

But get a look at the O2 sensor activity and the fuel trims; they may lead you in another direction. A smoke machine might be helpful if those tests point to a vacuum leak, or unlit propane around the intake manifold and other vacuum connections to see if the engine idle changes.