Ok, so my 07 XJR threw a P0171 the other day... here's what I've tried so far, and what I'm thinking of trying, but want some expert opinions before going much further...

Car threw P0171 after getting on the highway, so I took it home, came back to it that evening and got it back on the highway to see if P0174 would throw too... nope, just P0171... also, I'm not getting any "Performance Restricted" messages on the dash and seemingly the car drives pretty normal... Before the code popped, I had noticed it taking an extra turn or two to cold start, but nothing that worried me too much as we start getting into the colder months (though by no means cold here in Arizona).

I'm confused as to what would only throw P0171 and not 174, but also wouldn't throw the Performance Restricted messaging...

I've cleaned out the air filter, cleaned the MAF using MAF cleaner, and put a bottle of seafoam in her to have a go at injector cleaning... I've only driven about 25 miles since the code was thrown, so not sure if that would be enough time to reset it or not.

Other things I'm thinking of doing:
1) Check fuel pressure - But I don't have a gauge for this (also, can anyone post a picture of where the schraeder valve is on this car, can't seem to find it, including searching the workshop manual and this forum?)

2) Buy an OBDII reader to check out LTFT numbers... Not sure what this might tell me other than if it's fixed (since I don't know what it takes to clear the check engine light/code without one of these)

3) Smoke test it... though I don't have a smoker and so would have to take it to a dealer for this

Other thoughts? Advice on how to narrow this down?

Thanks in advance

 

Without the OBD tool you're semi-blind.

 

I suppose that's true. Guess I can order one off amazon.

 

Hi KarmaPolice,

At the link below you can download the full DTC Summaries manual which gives possible causes for each fault code:

https://www.google.com/url?sa=t&rct=...03388427,d.cWw

There are some possible causes that are more likely to trigger either P0171 or P0174 but not both, such as an exhaust leak before the catalyst for one bank but not the other, or a fuel injector restriction. But it is also possible for an upstream problem like an air leak to trigger only P0171 or P0174, for example, an O2 sensor for one bank might be more sensitive to a slightly lean condition than the corresponding O2 sensor for the other bank.

Here's the page that shows P0171:



Please keep us informed.

Cheers,

Don

 

Usually if PO171 and PO174 are the codes, its a vaccum Leak. If you have PO171 alone its running lean on bank 1. If you ruled out the leaks and MAF Sensor, then look into your O2 sensor Bank 1. But I would start with changing the O rings for all the hoses on the intake manifold.

On mine after changing everything It turned out to be a faulty MAF even though it was brand new it gave incorrect readings.

Note: the Crankcase vent valve naturally makes a hissing noise which is completely normal but can confused you if you think its a leak coming from that area. I also changed this to a brand new unit but wasn't the problem

Its a tricky one good luck

 

My P01701 was a leak at flange on exhaust down pipe right before O2 sensor pulling in extra air giving a false lean on that bank.

I went through all the topside troubleshooting, always skeptical that vacuum leaks on items common to both banks could only show up with a lean code on just one bank. However, I read on here that top side problems may affect banks differently, or not exceed limit for throwing code on both banks.

One helpful test for me once I had OBD was to feed some propane into air intake and I saw immediate negative STFT on both banks (taking away gas, due to extra propane fuel). That showed me 02 sensors were responding properly. It was good cross check since it's unlikely both bank's O2 sensors would go bad at same time. BTW, I leave the Torque Pro app running and displayed almost all the time. It's a great way to really learn what engine is doing, from fuel trims to true coolant temperature (as opposed to idiot gauge), etc. It's a great "early warning" system before you get to throwing codes. An Elm27 for $10 on Amazon and $5 for Torque Pro App gets you decent OBD functionality. Good luck....and enjoy

 

Usually air leak/leaks,smoke test and see what happenes..Air mass meters do fail if you have no leaks monitor your short and long term fuel trim.

on the older cars 04-05 xjr i have had a p0171 be a throttle for some reason it would flag a lean code and it ended up being a throttle,i personally had 2 cars and this issue.This was something the factory hotline tipped me off with many years ago.

 

teck4jag

I gave you a "Thanks" above for I have the same problem--throwing a P0171 only.

Could you go a little more into the throttle story a bit more--what to check etc.....


Cheers

 

Chuck,

See posts #4 and #6 for the possible causes of P0171 listed in the DTC Summaries manual and the one that caused Quantico's P0171.

Cheers,

Don

 

quantico--

I assume it was a typo, but did you mean an ELM327 in your recommendation, not an ELM27. Also, there are so many of these to include the TorquePro App, which is the best and easiest to use?

Thanks

 

Hi Chuck,

Since Quantico has not yet responded, I'll offer my experience. I'm using one of the more commonly-available ELM327 devices like this one, available from numerous eBay sellers at various prices:

ELM327 V2 1 HH OBD 2 OBDII Car Auto Bluetooth Diagnostic Interface Scanner Tool | eBay

It works well with the Torque Pro app running on my Android phone, and it's so cheap that if it fails I'll just buy another.

Cheers,

Don

 

This is one I have and works perfectly with Torque Pro and

 

Don--
Thanks for the heads up on the DTC Summaries, however I see that the recommended summaries are for an 04. I know more then likely most are the same for my 05, but before I print out the 153 pages, is there a 05 update or can I go with these?

Chuck

 

Hi Chuck,

I'm not aware of a '05-specific DTC Summaries manual available for free download, and that 153-page version is the most complete one I've found, with not only the P codes but the B, C and U codes as well. As far as I know, there are no substantial differences between the '04 and '05 Engine Management Systems, so the '04 manual should apply to your '05. I'm attaching a DTC Summaries Manual that contains only the Powertrain (P) and Chassis (C) codes, but indicates that it applies to the new XJ 4.2L models from the 2003 (U.K.) model year onwards.

If you have any doubts, you could compare the EMS schematics for the '04 and '05 models in the Electrical Guides:

2004 Electrical Guide:

http://www.jagrepair.com/images/Elec...al%20Guide.pdf

2005 Electrical Guide from VIN G34528:

http://www.jagrepair.com/images/Elec...al%20Guide.pdf

Cheers,

Don

 

I think the next main change was 2006 (for V6 and another for V8).

There's a bigger one than the one Don's just posted - I think it was just updated in 2008 by adding another 40 pages.

Looks like it's not too big so...

(I think this ought to be added to the forum - larger files area?)

 

JagV8,

Thanks! I hadn't seen that expanded manual. As you suggested, I'll ask Graham to add it to the downloads and will provide a link in the 'HOW TO' quick links.

Both the 112-page and 152-page manuals you and I just referenced contain only the P and C codes, they also include codes unique to the X-Type, and they lack the clear "Possible Causes" column of the 153-page XJ DTC Summaries manual, so the actual X350 information is more limited and more technical. Probably very helpful for those with the ability to monitor detailed live data, but perhaps less helpful for everyone else.

I realized the link to the 153-page manual in my previous post was broken, so I've fixed it there and will add it again here. I'll ask Graham to upload this one also, so we'll have easy access to all three manuals:

https://www.google.com/url?sa=t&rct=...03388427,d.cWw

Cheers,

Don

 

Yes, the original one you posted has that extra info - it looks like the individual codes PDFs from JTIS have been joined into one.

I also have
Denso V6 2006MY (113pp) May 2005 - says S-Type & XJ
Denso V8 2006MY (119pp) May 2005 - ditto
Denso (I suppose V8 only as they're all V8) (130pp) April 2009 - New XK 2007MY on

in case they're not in the large file area

 

Good evening-

May be have been already checked, but may want to make sure that there is a good seal where the plastic part of the air intake meets the metal part of the intake (snout).

I had a similar situation once where the plastic tube was 'folded under' partially and was allowing air after MAF. (On the bottom/side where it was out of sight).

Thanks
Mag

 

Mag,

Did the air leak you describe cause only a P0171 code, or did you also have the P0174 code? Just curious, since an intake air leak so commonly triggers codes for both banks.

Cheers,

Don

 

If I recall correctly, it was the one code only.

Thanks-
Mag