Hello Everyone,

Recently I've been getting a pesky P0101 code, but only in a very specific driving condition. I'll be coasting downhill on the huge mountain highways of PA...... barely applying the throttle, hence the low absolute throttle position %. Very happy with my fuel trims and the engine is running perfectly, smooth as silk.

Is there anything, other than the MAF sensor, that I should be looking at? I installed a Delphi MAF senor 17K miles ago when I was getting a P0101, but that time the fuel trims were higher and increase as the engine went under load ( a sign of a bad MAF sensor). Could it have gone bad already? I was thinking of purchasing a Denso unit. I was going to check the resistance of the signal wire on the MAF harness, but got lazy.

I'm hoping there are people more skilled at interpreting the freeze frame data than myself or experienced the same problem. Misery loves company.

Thanks so much.

 

Definitely MAF. Try and clean the sensor w/ MAF cleaner or electric contact cleaner. Let fully dry before powering it back up

 

Thank You! This past Saturday I did clean the MAF with MAF cleaner, but it still pulled the DTC on Saturday night and then again on Sunday. Bummer, I guess I'll be ordering a new Denso unit.

 

real deal denso is 60 bucks. anything else is not worth the time

 

I'll be no help but I will be watching this thread in hopes you find the solution. I have had this same problem for years, I can reliably trip the code doing exactly what you described or just by having the cruise control on in the hills of PA, a drive I make regularly. My indie Jaguar guy gave up trying to resolve it, I do believe it is MAF related as it seems to happen slightly less frequently after a good MAF clean but I've never found a way to fix it permanently.

 

Earlier this year i started getting lean running codes, checked for vac leaks replaced a few of the small lines that were brittle, cleaned maf sensor , all was ok for a few weeks then code came back, had car looked at by jaguar technician he fitted a known good sensor, a few weeks later code returned, I have read a lot of only using Denso maf sensors, I searched the usual places and bought a Denso sensor $170 canadian, I took delivery and was surprised to see the part was stamped Denso , no part number on it and on the box it said made in Vietnam, anyhow it has been working fine since i fitted it, nearly 4 months, touch wood, oh I also fitted a new air filter,

 

Well the new Denso has been ordered and I'm really hoping it will solve the issue. I also going to install a new air filter, as well, since its been 17K miles since the last change.

BRGSuperV8, yeessss it only happens to me on those huge mountain hills on rt78. The car runs perfectly otherwise. I already downloaded the pinpoint tests from ALLData for the P0101 and the wiring diagrams. I usually run all the tests first before firing the parts cannon at the car, BUT I'm hoping my laziness to test doesn't cost me lol.

I'll definitely post the results!

 

I found a Denso OEM MAF for my XJR in Spain for $25 shipped

 

Great deal!! I order mine for $100, but still waiting for it to arrive. I will post results once it's installed and driven for a while.

 

Update: I've installed the new Denso and unfortunately pulled the P0101 code twice in 2 months. The good part is that I drive a LOT and for the most part the car drives perfectly and excellent fuel trims. I'm going to leave as is for now. I don't even reset the code, it actually goes away after 3-4 start ups after pulling the code.

 

P0101 can also often be caused by a vacuum leak. If you haven't already, I would do a smoke test or visual inspection of all the lines to see if you have any leaks, as you have seemed to have eliminated the MAF as a potential culprit.

 

Thanks Jacuar! I did smoke the engine and found a cracked line that was leaking. Maybe there are other lines that I missed. i may need to smoke again.

 

Cheers, I hope you isolate the problem!

 

Thanks! I just need to motivate myself to smoke the car again. The evil side of the brain tells me to take the XJ for a nice ride rather than fix her. The drive wins out most of the time. lol

 

Karl,
I have a parts car in Ontario if you need anything.
Rob