Should be interesting to hear what the dealer thinks. None of us mortals have access to dealer-level diagnostics. We can still do plenty of troubleshooting, often at a deeper level because our time is "free", more or less. Many times the troubleshooting guide will lead you to two choices but we don't have the diagnostic capability to know for sure which path to select. However, we can still make an educated guess based on probability, pattern failures, wind direction, forum comments, etc. It's not just blind guesswork. We also have the option to install used or rebuilt parts, while the dealership is generally limited to only new parts. In many instances, we also have the option to replace just a subpart on a larger assembly, while the factory policy may be to replace the entire main assembly at much greater expense. Fingers crossed they isolate the problem and it doesn't break the bank.

You latest reply didn't mention the TPS. Is the new eBay sensor still installed or did you swap back to the original?

 

Well the dealer has weighed in and here is what they had to say:

There was still an error code, P1121, and the engine was in restricted performance mode. The OBD reader I got was not clearing all the codes. They cleared everything and drove it for 15 miles and started it twice and they think it's ok now.

The very interesting take away from this is that the car has HIDDEN obd codes that are not visible with a regular reader and does not set the CEL and can only be read by the dealer. Also, the car can enter restricted performance mode (limp mode) which is different than the regular limp mode and doesn't show any error messages on the dashboard.

I will take pick it back up tomorrow but I don't think it's really fixed. I don't believe that them clearing the code is any different than me clearing it by taking off the battery cable. I expect if I started it a couple of times in the parking lot, where it is cold unlike the inside of the repair center, it will die again. We'll see tomorrow.

I asked them about the mass air flow sensor being a possibility but they didn't think that the P1121 error code had anything to do with the mass airflow sensor DESPITE the Jaguar issued troubleshooting manual specifically describing p1121 as: TP Sensor signals inconsistent with MAF
Sensor signals.

I had a cold today so I didn't go pick it up today.

 

I'm not fully buying the dealer's explanation. A major impetus behind OBDII legislation was to create a standard access platform for any emissions related faults. In other words, an OBDII tool is supposed to be able to read emissions fault data on a '96+ Ford, Chevrolet, Fiat, Lamborghini, etc.

Manufacturers can go beyond that and create codes and other data that can only be read by a proprietary tool, but if it's emissions related, it has to be accessible to a standard OBDII tool. Lots of other systems (like climate control, adaptive suspension, etc.) need proprietary readers, but they have no effect on emissions. Nearly everything on an engine is emissions related and thus can't be proprietary (oil life monitoring is one exception that comes to mind), so I have my doubts about what they told you.

Let us know what happens in the morning.

 

There are no hidden codes. But there are some bad OBD tools that decide not to report codes they don't like/understand. So far I see no evidence that your tool is doing that.

You can read the exact Jaguar meaning of P1121 for your specific car model in the free to download workshop manual / codes PDF. It lists all known causes, too. It relates to an inconsistency between TP sensor (which is deduced from 2 actual sensors) and the MAF / wiring harness fault.

 

Note also that disconnecting the battery does not erase the codes.

 

What you say is true in regards to the law. However, companies break the law all the time. Look at Volkswagen with their emissions cheats.

Anyway, I picked up the car today. It started just fine while it was in the shop. I then took it outside, opened the hood, and waited for 8 minutes. I then started the car again and the problem is right back. Everything happened exactly as I expected. I took it back into the shop again. I told them to look at the mass air flow sensor in the cold.

I'm buying a new mass air flow sensor now. I'm not going to try the cleaner because symptoms point to a filament in the process of burning out.

 

Yes there are because the dealership has proven they can read codes that I can't. And the code is even the same code that I got before (p1121) so it's not a code that my code reader can't understand. There is some sort of pre-pending secret code in the computers that is not available to regular OBD readers.

 

So, um, has anybody ever mentioned you argue like a woman? It's an amazing skill, don't get me wrong. I am in awe of a woman's ability in such endeavors. Just wondering where you got it. You see, it's like how my wife and I could be making plans to see a movie and I mention how I don't really care for some actor. Before I know it, the conversation heads down a rabbit trail that ends with me in trouble over something my brother did five years ago at a family shindig. And she can even remember what I was wearing at the time.

Very interesting. Sorry it failed again, but glad to hear it happened there. What did the shop have to say?

 

It's hard to argue facts against someone who just thinks otherwise. You're plain wrong but I give up with you.

 

Well you certainly have made your repair much more expensive than needed. Have you finally learned anything? Like following the codes?

There are no hidden codes. There ARE code readers with different capabilities. I run Scan XL with the enhanced Ford package and can get nearly all codes the dealer can. But I am still limited because my tools are not as good as the dealer stuff.

You number one problem is you and your refusal to learn how the car actually works!
.
.
.

 

Well how did you make out?

 

Veering slightly off topic here, but VW's cheat was for their own benefit. It let them seemingly meet very restrictive standards at a lower cost than their competitors, and thus increase their profits. In other words, the cars weren't getting the CEL (indicating high emissions) when they should have.

You're suggesting Jaguar has set themselves tougher standards than required, with double secret probation codes only they know about? This imaginary cheating would benefit them how? Might be time to step back from the edge and think that one through.

I'm not following your logic at all. However, I am trying to apply everything I've learned from dealing with my beloved wife's oh-so-feminine logic. So far all I've come up with is I should apologize and buy you jewelry...

 

Everything that occurred with me and this dealer is a fact. Everything you've said is just an opinion.

 

At what point in this thread did I ever refuse to learn how the car works? Never. It was my mistake that I some how had the incorrect idea of what the P1121 code meant but no one corrected me until kr98664 mentioned it.

 

Nobody has ever said that but you are mistaken about the nature of my abilities. I've been on the internet since 94 and on message boards before that. I'm a champ at arguing.

With regards to VW, I never meant to imply that VW's cheating was anything like what Jaguar is doing here because obviously they are not. VW's cheating was for material gain. Jaguar's secret codes are just to prevent to the CEL from lighting all the time and buggy programming which allows a car to be in limp mode without a CEL light or an error message. That's all. I've found that other cars I've worked on keep information to themselves too. A F250 I've been working on had a severe misfire but still would set no codes even though it was misfiring 90% of the time. Simple bad spark plug with that one but because I falsely believed that there was no misfire because there was no misfire code, I was checking all the wrong stuff.

 

Not so. There are no hidden codes etc just as I posted. You may believe there are but that does not make it so.

Why you would be so determined to stick to something wrong in the face of multiple people with far more knowledge of these cars is beyond me.

Whatever occurred between you and the dealer is nothing of relevance to this.

Still, if you're happy believing in these supposed hidden codes, you go for it. Good luck.

 

I had a secret code in Mercedes (check engine light was on), which my scanner ($1500 new) couldn't erase and local repair shop owner's scanner (new $5000) couldn't erase. I knew 100%, that fault was not there anymore.
I went to foreman mechanic at GM dealership and he could erase the code. I don't remember which scanner he used, it was not GM scanner. I paid him $30.


Yesterday I finally diagnosed exactly the same problem, RPM drop when pushed gas pedal. My scanner showed fuel pressure drop. I checked voltage going to fuel pump, it was increasing as it should, so it was definitely fuel pump problem (or dirty fuel filter or screen)

 

Great, but that was a Merc. Irrelevant.

 

Finally, something on which we can all agree!

All arguing aside, where are you with the car's problem? What did the dealer say after it acted up again? What is the plan of attack? (I mean to fix the problem, not against the many forum members trying to help...)

 

Just an FYI

OBDII scan tool only read the PID’s (Parameter IDentification) that has been given to them when the tool is made any PID’s not recognized by the tool is not seen and therefore not shown. As for the codes your OBDII tool sees are most of the time correct but the definition of the code it provides is not correct for every car. This is why it is important to tell everyone to give us the codes and not what you think they mean because for each code might have 2 definitions/meanings based on the vehicles manufacture. So to say the codes are secret is not necessarily correct to say they are proprietary to the ownership of the car manufacture is and for that reason it may not identified by your code reader. With that being said many of us have tools that can and will read all the codes but it comes with a price.

I should also note that Jaguar is not the only car to have this issue with the PID’s!!