I am new to the forum so posting this to relate my experience with the lean codes on Lr3.I have an 08 Lr3 with 64000 miles. While driving one day check engine light goes on, ran the codes and came up P0171 and P0174, looked for obvious leaks and find any. I looked for info on this forum and decided to clean the maf sensor , light comes on after a few miles. Decided to change o2 sensors,long story short the upstream sensor passenger side had to be torn out of the pipe get anew nut welded in and then replace the sensor, the bolt holding converter to manifold had been put in bent so that was also a pain to remove. So new sensors, light still comes on, next I replaced the pcv valve, no help. After spending 2 weeks to figure this out I removed all the click connectors on pcv hoses to tight rubber hose clamps to eliminate any pcv leaks, I sprayed penetrating oil along throttle body gasket and this went on both sides of the gasket meaning that is where the air leak was. I took the throttle body off and applied loctite 515 sealant on both sides of the gasket and reassembled the throttle body and cleared the codes again .The codes have not shown up again, during the process I noted that there is a lot of vacuum in the throttle system and any minuscule air leak will set off the codes. I did not need to replace any of the other parts but replacing them is getting me 23 to24 mpg on highway driving and about 15 mpg in town so I guess it was worth the changes . I hope this helps people who have had these codes.The throttle body gasket is the leak.

 

I've always suspected that little metal gasket. 23 to 24 mpg on the highway is downright amazing. Highest I've been able to get is 17-18mpg.

 

I got the upper O2 sensors at rock auto , Bosch at much lower cost, downstream were universal Bosch ones, 55 dollars each that I spliced to original connectors.Pcv valve is a beck and arnley and maf sensor all from rock auto . I also have a K&N air filter from Atlantic British in for last 2-3 years. I think with everything runs more efficiently the mileage has definitely improved. I do have new tyres also, Vredestein quatrac. These tyres are quiet and are a combination summer and snow rated tyre, the original Goodyear ones were useless that I got rid of after 20000miles

 

I'm surprised Atlantic British recommends K&N...

 

Just another update on the Lr3. I went to add oil and twisted off the filler cap and the filler neck also came loose, so I suspect that this is another source of the air leak since the filler neck basically screws into the valve cover and there is a rubber gasket between the neck and the valve cover.With my experience tighten the filler neck,seal the throttle body metal gasket and either replace the O rings in the pcv system quick connectors then look at the electronic things as I mentioned my old pcv valve is good and did not need to be replaced.I would never have suspected the filler neck if it did not come loose in my hand!

 

Thought I would add to the knowledge pool. I have smoke tested for these codes and found the EGR valve to have a leak between the valve and coolant body assembly. The 2 don’t technically separate so not possible to replace a gasket or add goop.

 

Yes I've found that too. Not sure if makes a significant difference, but, if after fitting new MAF (if it ever the one ordered ever arrives) there is is still a problem getting it to run smoothly I might look at trying to seal it some how.

 

Adding more info, I am getting these codes on my 05.
Replacing my leaking EGR and a leaking PCV hose didn't cure them. I have an outstanding issue with a bad coolant temp sensor and leaking water pump gasket that I am still to fix.

I also have the loose oil filler neck and further I have badly leaking oil seals for the valve solenoids. I have ordered new seals (Jaguar part number AJ82856) and will report back if fixing those leaks helps. I need to get it through smog so I can register it!

 

Adding some experience...

• Youtube videos on using long + short term fuel trim to diagnose a vacuum leak. I have an ODB2 tool that reads fuel trim. At idle, short+long trim values added to ~15%. If this combined total goes down, it confirms a vacuum leak.
• A land rover tech on another forum said a failing MAF gives lean codes AND transmission fault. If you just have lean codes, he didn't think it was a MAF problem and recommended looking for a leak and cleaning the throttle body.

I suspected this gasket too. My codes appeared two years in a row as soon as it started getting cold, so I suspect an issue with a leak between two metal surfaces. Last year I paid a shop to smoke text and replace the EGR valve. This year it came back so I am confident the EGR is good. I pulled apart the EGR to add gasket sealer and found the EGR return pipe is EXTREMELY WOBBLY after removing the EGR valve. I think 10+ years of exhaust vibrations loosened the bolts on the other end of the EGR return pipe where it connects to the exhaust. The pipe connects at the back of the engine by the drivers side firewall... I can't even see it but asked the wife to tap on the EGR side of the pipe and I felt around until I found it. There are two bolts, 13MM I think, that needed some penetrating oil and a longer handled wrench to tighten both bolts about 1/2 turn. I just tightened because access was so limited... I can't even imagine how to catch and replace the gasket on the exhaust side. This definitelty stiffened up the EGR return pipe. I did add gasket sealer to both metal EGR gaskets on the front of the engine.

Unfortunately, the lean codes came back. More research:

• On another forum a user recommended resetting the engine control module adaptations with my ODB2 tool (GAP IID). I did this and my fuel trim IMMEDIATELY fell to ~2% and I haven't had the lean codes return since.

SOOO... the engine control module adaptations were MAINTAINING THE LEAN CONDITION even after I fixed the leak! This may explain why so many forums say the codes will eventually go away. If you have a capable tool, clear these codes! If not, don't be discouraged if the lean codes do not automatically come back. Give it a couple hundred miles.

 

I checked, cleaned, and added lithium grease to the gaskets to help with maintianing vacuum.

I need to pass smog too. After the fix above I went in and my "catalyst" and "evap" sensors reported a status of "not ready" so they wouldnt pass me even though the engine was running without codes, etc. My county in Texas will pass witih one sensor not ready, but they fail for two. There are a couple different procedures for completing a drive cycle online. I'm going through each of these in hopes it will help one of the sensors kick in. Might want to give this a go before paying for a smog test

Range Rover Drive Cycle 2006 and newer

and here's another one from the D2 RAVE manual:
A drive cycle consists of start-up, vehicle operation (exceeding starting speed), overrunning and stopping. On OBD-II, a drive cycle is simply defined as starting the engine and driving the vehicle long enough to raise the coolant temperature by at least .

There are 4 sets of Drive Cycles (A – D):

DRIVE CYCLE A:
-Switch ignition on for 30 seconds
-Check with diagnostics for DTC’s
-Ensure coolant temperature is less than 60C/140F
-Start engine
-Allow engine to idle for 2 minutes
-Check with diagnostics for DTC.

DRIVE CYCLE B:
-Switch ignition on for 30 seconds
-Check with diagnostics for DTC’s
-Ensure coolant temperature is less than 60C/140F
-Start engine
-Allow engine to idle for 2 minutes
-2 light accelerations (0 to 35mph with pedal pressure)
-2 medium accelerations (0 to 45mph with moderate pedal pressure)
-2 hard accelerations (0 to 55mph with heavy pedal pressure)
-Engine idle for 2 minutes
-Check with diagnostics for DTC’s

DRIVE CYCLE C:
-Switch ignition on for 30 seconds
-Check with diagnostics for DTC’s
-Ensure engine coolant temperature is less than 60C/140F
-Start engine
-Allow engine to idle for 2 minutes
-2 light accelerations (0 to 35mph with pedal pressure)
-2 medium accelerations (0 to 45mph with moderate pedal pressure)
-2 hard accelerations (0 to 55mph with heavy pedal pressure)
-60mph cruise for 5 minutes
-50mph cruise for 5 minutes
-Engine idle for 2 minutes
-Check with diagnostics for DTC’s

DRIVE CYCLE D:
NOTE: In the final phase of Drive Cycle D, it will be necessary to find a straight piece of road to ensure that:
-The speed does not drop BELOW 35mph
-No traffic conditions are encountered which will force the vehicle to stop
-No excessive use of is used to maintain the 35mph
-Lifting off the throttle completely is NOT required.

-Switch ignition on for 30 seconds
-Check with diagnostics for DTC’s
-Ensure engine coolant temperature is less than 60C/140F
-Start engine
-Allow engine to idle for 2 minutes
-2 accelerations (0 to 35mph with pedal pressure)
-2 medium accelerations (0 to 45mph with moderate pedal pressure)
-2 hard accelerations (0 to 55mph with heavy pedal pressure)
-60mph cruise for 5 minutes
-50mph cruise for 5 minutes
-35mph cruise for 5 minutes
-Engine idle for 2 minutes
-Check with diagnostics for DTC’s