So this morning, out of the blue, my check engine light came on. Cars was and has been running fine. So I pulled over and hooked up my OBD analyser. Yes, I keep it in the boot, just in case. Believe me, on an X308 you best carry an OBD scanner. I once managed to make it home with the the scanner hooked up and me hitting the clear DTC error every time the engine went in restricted mode.

This time it was a bit simpler. I found P0171; System to lean, bank 1.

I was in a bit of a hurry, engine was running fine, so I just cleared the code and drove on. I ended up driving another 140 miles and never got the CEL again. When I got home I run some more diagnostics and checked the fuel trims. With the engine properly warmed up, idling away the short time fuel trims were hovering around 0%. long ones around 4-5%. I think (?) that is pretty normal??

I did have one pending code P1111. I know about P1000 and P1111. I was just wondering when does it show show P1111? I know you will always have one or the other and it takes quite a bit of time to go from P1111 to P1000. I have some information (probably from this very forum) on what cycles, times, distances etc the car needs to run to go to P1000 status.

I thought, once you have P1000, stopping and staring the engine would not make it go back to P1111. Or will it. Because when I got home, I had driven about 55 miles from starting the engine.

Does the P1000 go back to P1111 every time the engine gets started? I thought only when there is a problem or when you disconnect the battery.

So although I have drive a good number of miles without the P0171 re-appearing, I am now worried that there is something else going on due to the P1111? Or is just there because I have not driven it far/long enough?

Thanks

Jeroen

 

I thought I understood about P1000 / P1111. But then I got them mixed up. P1111 means everything is fine!! I had them muddled up. So for now I think my P0171 was just random, unless somebody has some comments on those fuel trims or perhaps what else to check?

I have had a quick look at the breather connection and I will open up the air filter tomorrow. But I doubt it is a problem with those somehow.

Jeroen

 

Your fuel trims are excellent.

 

Don’t let it trick you. I had the same problem. same fuel trims. I did the same thing as you and it went away for a little bit and then came back so I checked it again got the same results and I went through the sequence for several months and it kept coming back.

did a couple of smoke Tests and found some leaks fixed them. But sure enough after couple weeks it came back. I can’t tell you if it’s fixed but it’s been gone for a couple of weeks. in my heart based on my experiences, I fear it will return, but my fingers are crossed.

 

Clean out the MAF sensor to begin with.

 

Usual stuff: clean the MAF sensor; check the air tube for leakage; clean the the throttle plate and bore; run a can of SeaFoam or Gamout's best through a tank of gas; replace the plugs if old. A guess: your injectors are dirty and are spitting instead of spraying; SeaFoam will fix that.

I had this problem on a SC Range Rover Sport: about every four months I would get this code or its brother, 172: reset and run some cleaner always fixed it.

OBD reader is in the glove box!!

 

Fixed it?? Sounds like the same thing I experienced with the only difference being I didnt run a can of cleaner after resetting the DTCs.

as I said, I wouldn’t get the fault code immediately after clearing the faults. I will get the check engine light and the fault code randomly. Sometimes several weeks to several months after clearing the code. The length of time in between faults varied and i could never figure out why it triggered at the specific time it triggered.

But reading the jaguar dtc tech docs i found that in order to throw that f asult code, you need to have a narrow but specific set of operating conditions before it even test for the faults. And those conditions might not all exist simultaneously for the test to run. and if it did run the test might not run on the next drive cycle so the back to back drive cycle fault reporting wouldnt be met so no DTC. Or if the entry conditions didnt remain for the required length of time ( due to my driving style for ex) it wouldnt count.

And coupled the requirement that the fault has to happen in 2 Separate drive cycles back to back theres more opportunity to delay flagging the fault. If I did manage to run the test and qctually did get a fault in one of those drive cycles, but then not on the subsequent drive, the counter starts anew and not throw a code.

so I’m not thinking that you fixed it by putting that bottle in your tank. I think you have the same results without the injector cleaner ie several weeks between faults

 

Thanks everybody for the comments and suggestions. I agree that usually once a DTC has shown up once, it is likely to return at some point in the near future. My Jaguar is at the paint shop till tomorrow for a small repair on the bumper. I will pick it up tomorrow evening and have a go at all the obvious causes. We are leaving for a short trip to the UK later this week. I will be doing about 700 miles in 4 days, so lets see what happens then. But as always I’ll be carrying my OBD scanner with me.

Jeroen

 

Some possible causes of a P0171 engine code are

• Vacuum leak
• Weak fuel pump
• Damaged or Broken fuel pressure regulator
• Clogged or Blocked fuel filter
• Faulty powertrain control module
• Clogged or Defective injectors
• Faulty oxygen sensors
• Clogged catalytic converter
• Problems with the mass airflow sensor

 

No. It means all the supported OBD monitors have set OK.

If any are not set you have P1000 and also many codes cannot be flagged.

Unlikely. Much more likely you have a fault.

Also, be aware what P0171/P0174 actually mean: more O2 in the exhaust gas than expected. That can be any of the causes Jaguar list in their codes doc.

 

As we are setting off tonight on a short three day, 1000 km, trip I decided to at least check a few basic things on my Jaguar.

Checked and cleaned the air inlet filter. I have a K&N filter installed, it was dirty but I have seen worse. I noticed that the contacts on the mass air flow meter were quite corroded!! So I cleaned them thoroughly.




A question about the Mass Air Flow meter. See below image. Where is the actual air measured. Is it inside that circular thingy? The little wires seem more like a temperature sensor than anything else. Or is this the actual sensor, but then again what is that circular thingy? Or to be very concrete, where do I spray my specially bought MAF cleaner?



Thanks

Jeroen

 

It's a heated wire, cooled by the air going in. The PCM measures the current/voltage.

There's also an air temp sensor.

PCM works out mass per time using both.

 

Yes, it is a sophisticated part but not as sensitive as
one might expect. Keeping the current good by cleaning
the contacts is a very good MO.