Hello Everyone:
My fault code P0101 is back. I had the MAF sensors and air filters replaced. Everything was fine. Then code comes back on when the car sits for awhile. Maybe a week or two. Then the engine light comes on. I know everything is new but can't determine why the code keep making the engine light come on and off again. I have read on this website that someone reset the engine light a couple of time and that fixed the problem. How do you reset the engine light code for P0101?

Thanks


Joe

 

Joe,

The reappearance of a DTC is normally because the cause has not been eliminated.

P0101 has no extended codes which helps by not requiring Jaguar level diagnostics to troubleshoot. Here's the description of Possible Causes and Actions from the Jaguar lookup:




Mainly air leakage or blockage or harness fault.

Any scantool should allow you to clear codes. Unfortunately this will clear everything and not just P0101 but the advantage is it also clears 'learned adaptions' which sets fuel trims back to factory default. Note that this is one the the recommended actions in the table and there is a good chance (provided no other cause is present) this will clear the code and keep it cleared.

Graham

 

How many miles on the car @JDog ? And what “performance mods” have you made?
Its not uncommon to think that the throwing of a code is a sensor issue…. but often the sensor is doing its job and there is another root cause at hand.

 

Buy a Elm ODM2 scanner (~$15 online) and you can check codes. More importantly you can check fuel trims to see if you have an air/vacuum leak - which i'm pretty sure is the root cause of your P0101 code.

 

Hello everyone:
Thanks for all your replies. Here is the story. I purchased the car unseen online over a year ago. Pristine, low miles(40K), one owner(engioneer), and talked in depth to the Jaguar service manager about all the services of the car. He reassured me it was pristine too. The car came in and I drove it for while maybe six to eight months, the P0101 code came up. I took it to my first jag mechanic. They really took advantage of me but I call that my tuition. Everyone has to pay before they learn. They replaced both MAF sensors and both air filters. With 40K miles, all you really had to do is clean the MAF sensors. I drove the car awhile and the code came on again. I was about to take it back in and the code went off. I drove the car for maybe a couple of months, everything was OK and parked it in my jag garage. It sat for maybe 3 weeks. Got into it for a drive and the code was on again. I have now reset the code from my Elm ODM2 scanner. Will see how long that lasts.
Guy: The has 43K miles on it with no mods.
gkubrak: How do check fuel trims for air/ vacuum leaks? I am pretty sure this is the problem too.

Second Question: I live in Houston and the temp here gets pretty hot. It is going to be in the 90s all this week. How much should the temp change when setting in Houston traffic? I notice that it goes from 198 cruising on the road to 208 setting in traffic. When should I start to worry about the temp? Is there anything else I can do to keep the temp lower? Change thermostats?

thanks everyone

Joe

 

Your temps sound ok. There’s a fellow on this forum that sells lower temp thermostats if you want to go that route.

 

Normal op temp is 208 -220 so you're good there.

 

@JDog , thanks. At 40K I think that would probably rule out a dirty throttle body.
And the air ductwork should be tight. The filters matched. The MAFs matched as well. The electronics connector clean and firmly connected. At 9 years of age in the Houston climate zone I’d be wondering about vacuum lines, connections, gaskets, etc.
Are you certain this the only code being thrown? I don’t use the Elm. Does it show all Jag codes?

Being that the service was done at a Jag shop… aren’t parts and labour covered for a year? and

 

You can check fuel trims using an elm. If the software you have doesn't do trims, change software.

 

Hello:
Thanks everyone for their input.
Sean W: Thanks for your input. I did not know the temp ranges that are normal. I was worried about 212 in stop and go. Now, no worries.
Guy: No, the car has not been in Houston for 9 yrs but for 1 year. I bought it in Kansas City and shipped to Houston. When I changed the SC coupler, I had all vacuum lines and connections checked and changed at that time. That is the only code shown on the scanner. I had the work done at a shop that works on jags not a jag dealer.
JagV8: I purchased a cheap scanner just to read and reset codes. I will purchase a better scanner to check fuel trims. I assume with a good scanner, checking fuel trims is standard.
Correct? Any suggestion on which scanner to buy? I have reset the code and all is well. Hopefully that is all I need to do.

Joe

 

Elm scanner is fine. I use the Piston app on my iphone and it shows fuel trims.

Check while the engine is warm. During idle, positive 10-20% readings would point to a vacuum leak. Under load, they would point to an air leak. Readings under 10% are fine if they are equal bank to bank.

Take it from someone who has deal with this code extensively. Deleting it won't fix the problem. And continuing to drive it may damage your CATS.

A smoke test pointed out leaking vacuum fittings and breather system leaks. A few years later, it came back and I found that just reinstalling the intakes and tightening everything solved the issue.

The rubber connector between the throttle body and T-piece is a known failure point.

 

This here, a smoke test is a surefire way to know and eliminate this as part of the possible cause. You can DIY with a $100 smoke machine and a compressor and I think there was someone on here that built one with a bike pump. Or any competent garage can do it. Sometimes paying someone for this is worth it because vacuum leaks can be annoying to trace.

 

Yes that was me haha.

 

There are multiple places for a vacuum leak on these after all these years. Unlike most men, rubber gets stiff as it gets old. You need to check trims to find left? right? both? Mine had a bad oring on an injector. There's a nasty little grey vacuum hose connected to the TB that's brittle as hell. Seriously, as said above, the only way to stop guessing is to smoke test it under strong pressure (more than a glove on the throttle body). If you do this, you'll find all of them, and there are likely a half dozen smaller ones that add up to a bigger one.

Good news: fixing all of them is easy on the NA, even the injectors -- can't speak for the R. But with a good smoke test, you'll know. Good luck.

(And seriously, the glove-on-the-TB results in missing some of the leaks.)