Hello all,

I currently have an engine light on for lean bank 1 and 2 - P0171 and P0174 codes. I’ve read just about everything I can find on it to try and troubleshoot it myself however the issue persists.

I’ll do my best to break it down into something that makes sense:

VEHICLE BACKGROUND:
2005 LR3 SE
232,000 miles

Previous owner was the owner of a local indy LR shop and took exceptional care of the vehicle. He had much of it’s history prior to his owning it and did the work on it then, before it was his. He then did more to it and it came with a very comprehensive list of things he did, including re-hosed the entire engine, replaced transmission, upper/lower control arms, brakes, tires, alternator, e-brake fix, t-stat, new radiator, plugs, roof drains, MAF sensor, heated windshield, and petty much everything you could want to do to make sure its tip top shape.

It runs strong, spins quiet like a top and other than the codes, its amazing. Last summer it took us 2,000 miles in 5 days without skipping a beat.

PROBLEM:
The problem started with P0174 then shortly after clearing it with the IID tool came back and brought it’s friend, P0171. I noticed a very slight rough idle at stop lights and the RPM’s would dip low, near 500’ish. Never stalled. The rough idle has since been fixed with the cleaning of the MAF and TB listed below.

Both codes would be cleared then return and seemingly random intervals - sometimes it stays off for a while, sometimes not so much. The best success had it off for the longest time after resetting the values. But the codes returned.

Otherwise the truck continues to run strong and I notice no lack in performance, at least that I can tell.

TROUBLESHOOTING COMPLETED:
So after reading exhaustively about the P0171 and P0174 codes I realized it could be numerous things, anything from the MAF and throttle body being dirty, to bad exhaust O2 sensors, plugs, coils or a cracked hose. I’ve done the following:

1. cleaned MAF - a few times
2. cleaned throttle body - a few times
3. cleared codes and also hard reset the truck - at different times
4. ran fuel cleaner through the tank twice
5. ran a tank of 93 ethonal free gas ($6 a gallon!) with the fuel / TB cleaner
6. replace the MAF with a yard find as to rule out the existing one
7. visually inspected all the hoses for obvious cracks
8. checked fittings, connections and seals from the air box through the TB and then any other hose i could get my eyes and hands on.
9. reset active values
10. driven around and recorded sensor settings from the IID tool (I will attach them if I can figure it out).

OUTCOMES:
The engine light and codes are back and return almost immediately after being cleared now.I think the replacement MAF has made things worse so I’ll be swapping in the first one again because I noticed a distinct different in how fast the codes returned after I swapped them - almost immediately. I also noticed a new, quick surge of power when stopping at red lights after the yard find MAF. So that’s gotta stop. Otherwise, the truck continues to run very well.

NOT YET DONE:
I’ve not smoked tested it as I don’t have a smoke machine and the hoses are newer. I have not checked or reseated plug/coil connections and I have not replaced exhaust O2 sensors, or any O2 sensors as I’m not sure where they are exactly or if that’s the issue.

IID TOOL READINGS:
Warning up front, I have no idea what these readings mean as I can’t seem to find the ranges they are supposed to be within. I did read a general article on the air/fuel mixture but still can’t equate that to what I’m seeing. I tried different combination of monitoring values to try and correlate if something was starving or failing at different points in the power band although nothing jumped out at me, but again, I have no idea.

Read on 02.05.22

• O2 equivalence ratio - bank 1, sensor 1: 0.955
• O2 equivalence ratio - bank 2, sensor 1: 0.953

(these fluctuated during driving)

Read on 02.14.22

• Accelerator position: 25%
• O2 equivalence ratio - bank 1, sensor 1: 0.951
• O2 equivalence ratio - bank 2, sensor 1: 0.956
• O2 Oxygen sensor current, bank 1, sensor 1: -31 mA
• O2 Oxygen sensor current, bank 2, sensor 1: -27 mA

(these fluctuated during driving)

Read on 02.14.22 after the above

• Mass air flow: 6.2 g/s
• O2 Oxygen sensor current, bank 1, sensor 1: 20 mA
• O2 Oxygen sensor current, bank 2, sensor 1: 16 mA
• O2 sensor output voltagem bank 1, sensor 2: 0.7 v
• O2 sensor output voltagem bank 2, sensor 2: 0.7 v

(these fluctuated during driving)

Read on 02.14.22 after the above

• RMP: 1701
• MAF: 26.2 g/s
• O2 Oxygen sensor current, bank 1, sensor 1: -31 mA
• O2 Oxygen sensor current, bank 2, sensor 1: -35 mA
• O2 sensor output voltagem bank 1, sensor 2: 0.7 v
• O2 sensor output voltagem bank 2, sensor 2: 0.7 v
• (these fluctuated during driving)

I attached the PDF output from the logs above if that helps.

NOW WHAT?
So I need some help please. I’d like to try and do as much as I can on my own before taking it to the shop. Am I reading the right things from the IID? Does any of this make sense?

What else should I look for? What else should I scan and post?

It's going to sit until I can mess with it this weekend.

I appreciate whatever knowledge you can throw my way.

Thanks!

 

Have you tried:

• Replace MAF Sensor with a good replacement, then reset adaptations?

 

MAF, grab a Denso. 197-6020 is the part #, don't have to pay more because the box says Land Rover.

Also might be worth replacing the PCV valve. Part is less than $50 and takes 5 min to do. 6" disc on top of the passenger side valve cover. Just takes 2 torx screws to swap it out. if it's bad it could cause a lean situation

 

Thanks guys.

I’ll grab a new MAF and maybe the PCV. The PCV was for sure new before I bought the truck a year ago and I think I checked it wasn’t oily when I cleaned the TB.

Anything else to consider?

 

...just resetting the adaptations after the new MAF is installed.

 

Yep. I’ll reset it after the new MAF is in.

 

So the Denso site says the 197-6020 does not fit it. Thoughts?

 

22204-22010
197400-2030

^ Those numbers are both stamped on the ones I get. But I do think there are variations on the numbers. I also think that generally if it fits properly, its probably going to work. It's not like MAF sensors are overall that radically different.

 

To add to your list of possible causes, I would add dirty/failing injectors. That's what ended up curing my persistent and intermittent lean codes when I had them. Tried everything else.
An intake leak could certainly also be it. They can leak from the main airbox housing pieces, not just hoses Really hard to find without a smoker - you can get those for about $100 though... or half an hour at the LR shop

 

I just had the same issue, I replaced the air filter it was about time. Tried the cleaning it and cleaning the throttle body, but replacing the MAF sensor fixed it. I just got one from local parts store, large chain and it's a lifetime guarantee. a few months in and no issues.