Ok guys, new to the LR word...I picked up a 2016 LR4. Its interior and exterior are great. I really enjoy the vehicle. It's got some issues though and I'm having trouble tracking it all down. Maybe you guys can help me, it'd be greatly appreciated.

First I was getting the lean at idle codes for both banks and it was idling really rough. I replaced the PCV valve and the idle seemed to settle out. Runs great and idles smooth. but about 10 miles later....

I threw two codes, 1 is a P0128 coolant thermostat and a bank 1 lean code. I don't believe they would be related, but if I'm wrong please tell me. So a couple things I've found....

1. I have a small coolant leak at the LR049990 hose. I ordered the brass elbow thing and will replace it. I wouldn't think that would cause any issue though.
2. The used car dealer I bought it from said they replaced the thermostat in the shop. Chances it already failed??
3. There are two vacuum tubes from the back of the engine, one on passenger side, one on drivers. They both run forward and the passenger side connects right above the throttle body. The one on the driver's side connects to the airbox I believe. It's currently not connected on mine, and even though it looks like everything would line up and it should connect it appears like there is a fitting or something missing. Could this cause the lean code?

So any thoughts on those two codes would be appreciated. I've been doing tons of research, but I feel like I'm just reading in circles and not getting anyware. Also I have an icarsoft diagnostic tool with the LR software if that would give us any more information.

 

Glad you’re getting on top of that leak.
Also, these engines can easily have an airlock in the cooling system.
As for fuel trims , absolutely a failure in the vacuum system can be the cause.
Check your PMs.
cheers!