Got these codes a month or two ago and been working on a solution ever since. I read the bulletin from 2007, and have checked everything I can imagine. Using an OBD tool I checked the fuel trim logs and the long term fuel trim is positively correlated with RPM's. So, I did a Seafoam cleaning through the throttle body, and ran a few cans of Seafoam through the gas tank. Then I did an induction cleaning with an OTC 7448. I also replaced the MAF, and changed the spark plugs and filter. I checked the O-rings on the dipstick and Oil filler tube and they look fine. I can't find any vacuum leaks anywhere. It also idles a tad rough and the lights flicker at idle, other than that it runs fine. So i'm at a loss...

Any insight from the masses?

Thanks!

 

Few questions:

1. How many miles on the truck?
2. Have you changed the PCV valve yet?
3. Have you used the OBD tool to monitor the O2 sensor readings?

Also, a couple of observations... I've heard of other people who have said they had similar lean codes that were the result of a bad PCV valve. It's also one of those things that's just good preventive maintenance to replace anyway and it's relatively inexpensive, so I might do that regardless of other stuff.

The first thing I think of when you say that the engine runs a tad rough and the lights flicker at idle is that you have a bad battery. However, if this has been going on for a while, then I would assume your battery is okay. You might want to take a look at the voltage though. Also, I would take a close look at your negative battery cable. I have heard of people who had their negative cable completely corrode. It wasn't really visible from the outside, but stuff would change when they moved the cable with their hands... upon taking it off, they could tell the inside was completely corroded.

 

Throttle Body...?

 

Its a 2008 HE with 100k. I haven't changed the PCV yet. Yes, I have logs of the O2 sensor reading, but i'm not really sure what i should be looking for.

I did check the battery cable, and will have the battery tested this weekend.

Thanks for your help.

 

And this.

If it were me, I would start with Houm's suggestion of cleaning the throttle body. I would also go ahead and replace the PCV valve. If you have 100k miles on the car and it's never been replaced, then it's certainly time.

 

Change the PCV valve whether you need to or not if it is original. It was a huge problem for me a month ago, and never thought that little POS could cause all those issues but it did!

 

OK...so I swapped out the PCV valve and cleaned the throttle body. Then I cleared the codes and went for a drive, but the light came back on. Long term fuel trims on both banks are running really high, in excess of 12+%.
EGR valve? Any way to test that?

 

I bought my LR3 with similar symptoms. The dealer I purchased from changed MAF, and PCV valve, reset codes and had no change in results (fuel trims out of limit throwing CEL after 10 miles of driving). No obvious signs of a vacuum leak, as short term trims at idle were in good shape. This lead me to believe there is some miscommunication about throttle position under different load conditions.

I followed same steps as you once I negotiated a new price for a rig with a CEL they couldn't clear. Got it home, did the throttle body scrub down.. and also cleared all modules, by disconnecting both leads from the battery and running a jumper wire between the two leads (not the battery posts). Leave it for 10+ mins to ensure all power is drained from various capacitors in the system and then reconnect and try again.

The intent here is to force the throttle body to re-learn open and closed position. 6,000+ miles later and everything is solid. There is a chance this won't work for you... but its easy cost effective next step.

Hope that helps

 

I tried that this evening and the CEL code came back on. Thank you for the suggestion though!