P0170 fuel trim and CEL

My 2016 LR4 SCV6, on a trip to Seattle, threw the check engine light. GAP tool reveals that it is the P0170 code, the bank 1 fuel trim. I cleared it and it immediately seems to come back on the GAP tool, although the CEL doesn’t come back on.

i vaguely remember that it might have to do with the charcoal canister, but a search here didn‘t find that. I do wonder a bit, because I recently filled the tank with a Gerry can, which obviously doesn’t have automatic shutoff. I listened for the telltale tone of the fuel coming up the neck and stopped it before it overflowed the neck, at least.

Does anyone have a suggestion as to where to start looking for a problem? Or should I just wait and see if the CEL comes back on on the trip back down to Portland from Seattle?

Check your actual fuel trims using the gap tool. Run short term fuel trim and long term fuel trim and engine rpm. graph live values at idle, then hold it at about 1500 for maybe 20 seconds, then hold it at 2500 for maybe 20 seconds. take a look at the results and see if its running lean (positive fuel trim) or rich (negative) at idle, and notice what happens as rpms increase. should give some clues about what’s going on.

I don’t know if this is going to work, to share the PDF this way. But here is what I have. Throttle wouldn’t let me maintain 1500, so it ended up being about 1850 for the mid range.

I appreciate the help!

Those fuel trims are still basically within normal range (as I understand it) - maybe on the edge of being a little too lean, but nothing that should trigger a CEL.

The engine code seems to relate to a plausability failure. There are several subtypes listed in the manual, but they all relate to exhaust leak or oxygen sensor failure (or oxygen sensor circuit failure). p0170 corresponds to bank 1.

There have been a couple of reports on this forum of the manifold bolts shearing off, which can lead to an exhaust leak. I suspect it might have to do with motor mounts going bad, but not sure.

But, the simpler solution might be the o2 sensors, so maybe go for that first.

At any rate, I think you should be fine to drive it home. Obviously, if you get a flashing CEL or start misfiring, smoking heavy, etc., that would change things.

Thank you. I had already driven back to Portland by the time I posted that, and should have said so. But there is still some urgency because I have a trip to Moab that I leave for this Friday.

What you wrote mirrors what I was finding. It further looked like it might be the MAF sensor or, if it is the O2 sensors, likely the one closest to the engine on the driver’s side? Which, naturally, is going to be very hard to reach.

On the highway back from Seattle, I did record a log of the Lambda, attached here. There IS a strange spike early in the attached data on Bank 1, but other than that things look pretty normal to me. It’s almost like there is a hiccup in fuel delivery at that point that was quickly corrected.

Could be a MAF, but this code is bank specific and MAF malfunctions generally affect both banks (air from each “side” is combined when it enters the engine). So, if I were replacing things, I’d go for the o2 sensor first. I would suspect the lamda (pre-catalyst) o2 sensor which is closest to the engine, although the book says it can be post-cat as well. Bank 1 is passenger side.

I forgot that someone had helpfully posted that 1 was passenger side. Thank you!

Could be the spark plug, fuel injector bad on Bank 1 or Air leak. Simple way to do first is smoke test for a leak and go from there.

I ordered new Bosch sensors from Rock Auto, and managed to get the old one out last night on the passenger side. Geez...that is not a job for a guy with hands my size. And I don't really see how to do it on the driver side without removing the driveshaft. I'd rather replace in pairs, but I don't know if I'm going to be able to.

Do people reset anything other than clearing a code after replacing a sensor like this? I've never needed to with any other car, but it's a Land Rover, so...

Well, the same code has tripped repeatedly on my way here to Moab. No apparent problems, and it seems fine for awhile then trips. The O2 sensor #1 on bank 1 must not have been the problem. Nuts…

Hopefully not going to raise issues to run trails down here.