CEL - Fault Codes PO172 and PO175 - 2012 LR4

[MarcusTriton]

I just got back from a 1000mi trip traveling in my luxurious 2012 LR4 and with the last 90miles to go, I fill up with gas, even though I had just a little over half a tank and then after about 10min. down the highway my CEL come on. I had no CEL on until just after the fill-up. Even with the CEL on the LR4 was operating just fine, so I pulled over and checked under the hood and underneath the chassis, just in case, and found nothing out of place. When I got home I hooked up my code reader and found Fault Codes PO172 and PO175.
What do you think is causing these codes...?(scan tool says "Oxygen Sensors Bank 1 and 2, detecting a rich condition")
What do you think it is...?
Oxygen Sensors...?
Dirty MAF...?
Vacuum leak...?
Dirty Fuel injectors...?
Fuel pressure delivery(P.S. - I did have the fuel tank flange replaced in January)...?

What should be the initial next step in diagnosing this problem...?

Thank you in advance for any insight into this dilemma...

 

[Aderry]

Did you ever get this figured out? I’ve been chasing the same codes for a while.

 

[MarcusTriton]

Did you ever get this figured out? I’ve been chasing the same codes for a while.

The CEL went off by it self...and then a week later came back on... and then a week later went off again...
It is now off......and all that time my 2012 LR4 ran fine... just had the CEL on...
When it 1st started to happen, I believed it was bad gas(87oct) that I got from an of-the-beat gas station so I ran the gas tank down to 1/4 full and added 93 octane gas to fill it up and 20oz.'s of Techron and waited...
(BTW)My cheap wi-fi scan tool just gave me the codes. My next step, if it happens again, is to clean the MAF sensors, and if that doesn't work, take to my local repair shop and have it scanned with their $12k scan tool to pinpoint the problem...
Good luck with yours...

 

[SMorelli]

Did you ever get this figured out? I’ve been chasing the same codes for a while.

I have a 2015 LR4. It started to stall at low revs predominantly in the cold weather and within 10 mins of the first start of the day. Always as I tried to pull away at a junction or traffic lights.

It threw mainly low fuel pressure codes and the display would often switch to the al terrain page. It always re-started and usually ran all day with no issue.

I looked at everything obvious including the fuel relay (it was clicking in & out) in the fuse board to avoid spending $$$.

The first summer the problem disappeared and reappeared in winter. Once started and stalled it seemed like it would run no problem all day and never stalled at speed.

The following summer it continued to stall with increasing frequency. I had a code for O2 sensors and they were due so changed them. This did not fix the issue.

I put it into a specialist in Jan 2023 (very cold at this time of year in Canada) he said it runs fine and wanted to buy it from me. ($500 for driving it back and for to work for 3 weeks!!!!) It stalled two days later and continued to do so including not even starting until the weather got above -10DEGC.

Frustrated I put it into a garage that I trust and had him change Low pressure fuel pump, low pressure sensor, low pressure pump controller & High pressure/temp sensor.

Still it stalled!!!!!!!!

I changed the fuel cap in case the tank was Vacuuming........still stalled!!

I went back to the workshop manual and reviewed the low-pressure system and the only part I had not replaced was the fuel relay but I could still hear it clicking in and out.

A little further research on relays and I found a source that said never trust that just because its energizing that its good.

I removed the relay and energized it with a 12 battery and measured the resistance across the contacts. Each time i energized it the resistace jumped from 0 Ohms (good) to sometimes 600 Ohms (bad).

Bingo!!!!!! the intermittent failure was dirty/bad contacts on the relay that feeds the low pressure fuel pump controller.

I opened up the relay and confirmed this was the issue and even cleaned them with brake cleaner. I then swapped the relay with the same on that feed the blower to test my findings and the problem vanished.

I bought two new relays from LR $35ea and now have my car running like a watch!!

I learned the hard way, I hope this helps you guys. Just swap the relays to test yours, no big deal if the blower doesn't work if it proves the issue.

 

[MarcusTriton]

I have a 2015 LR4. It started to stall at low revs predominantly in the cold weather and within 10 mins of the first start of the day. Always as I tried to pull away at a junction or traffic lights.

It threw mainly low fuel pressure codes and the display would often switch to the al terrain page. It always re-started and usually ran all day with no issue.

I looked at everything obvious including the fuel relay (it was clicking in & out) in the fuse board to avoid spending $$$.

The first summer the problem disappeared and reappeared in winter. Once started and stalled it seemed like it would run no problem all day and never stalled at speed.

The following summer it continued to stall with increasing frequency. I had a code for O2 sensors and they were due so changed them. This did not fix the issue.

I put it into a specialist in Jan 2023 (very cold at this time of year in Canada) he said it runs fine and wanted to buy it from me. ($500 for driving it back and for to work for 3 weeks!!!!) It stalled two days later and continued to do so including not even starting until the weather got above -10DEGC.

Frustrated I put it into a garage that I trust and had him change Low pressure fuel pump, low pressure sensor, low pressure pump controller & High pressure/temp sensor.

Still it stalled!!!!!!!!

I changed the fuel cap in case the tank was Vacuuming........still stalled!!

I went back to the workshop manual and reviewed the low-pressure system and the only part I had not replaced was the fuel relay but I could still hear it clicking in and out.

A little further research on relays and I found a source that said never trust that just because its energizing that its good.

I removed the relay and energized it with a 12 battery and measured the resistance across the contacts. Each time i energized it the resistace jumped from 0 Ohms (good) to sometimes 600 Ohms (bad).

Bingo!!!!!! the intermittent failure was dirty/bad contacts on the relay that feeds the low pressure fuel pump controller.

I opened up the relay and confirmed this was the issue and even cleaned them with brake cleaner. I then swapped the relay with the same on that feed the blower to test my findings and the problem vanished.

I bought two new relays from LR $35ea and now have my car running like a watch!!

I learned the hard way, I hope this helps you guys. Just swap the relays to test yours, no big deal if the blower doesn't work if it proves the issue.

Great story...Thanks...
Would an advanced scanner have picked this problem up?