Well this is a strange one, recently picked myself up an XJ6 Executive from a seller who stated the car has an issue with its Transmission Control Module, it idles very rough and may stall occasionally, he said.

I bought it as something I thought could be a wrong diagnosis, thinking, idle control valve, coil, spark plugs, fuel pump, easy fix. . . .

After exausting these avenues I took it to Jaguar Specialists Les Paul, who stated this model does not have a Transmission Control Module, YIKES.
They then did a £60 diagnosis and said were not sure P1020, and some other error code they said kicked up which indicate Lambda sensors and Air Flow meter total cost £1100. Hmmmm. He said the Lambda sensors arent swinging (more on this later) He goes we can try to fix the car starting with the lambda sensors but cant guarantee a fix.

I also had a problem with the car I felt not going into 4th gear, I could be imagining the limp home mode, Les Paul then said impossible, and this car has a 5 speed auto, Hmmm, this I know is wrong, wrong, wrong, so I now lose faith in this guy and buy myself a code reader and get cracking.

I can drive the car fine for 30 minutes then it starts stuttering and the engine warning light comes on and loses power drastically, under braking below 1500rpm it may stall. The more its driven the worse it gets, how weird.

My code reader says P1621 error code, while driving the code reader shows voltage readings from two lambda sensors relatively the same voltage and swings, meaning all seems OK with them right???? Surely if the lambda sensors where out they would give no reading . . . as was claimed by Les Paul, who by the way are crooks it would seem, how sad. I wish the fault was a Lambda sensor fault as I quite liked the diagnosis guy

I looked up P1621 and it says some jazz about long term memory performance of PCM???

Do I just replace the ECM????? I only just today replaced the air flow meter, no change

Any Harry Potter boy wizards out there, but I reckon I really need Gandalf

PS Iam replacing the Lambda sensors on Sunday, BTW anyone know how to get these buggers out?? I have no 17mm lambda sensor socket nor have ever seen one

 

Oh yeah while I was taking live readings and driving along, as the problem got worse, all values on the code reader froze and sometimes it would reset itself while trying to read the misbehaving car

Makes me think ECU??

 

After reading some posts from some very clever people on this forum, I realised that I may have a dodgy coil as when it heats up it arcs and gives a P1621 code.
How do I test a dodgy coil, dont want to buy 6

OR

My crankshaft sensor is dead, how would I test that

 

I bought the memoscan U581

 

crystalvision:
What is an "executive"? Is it an x300? which engine? AFAIK, All X300s with 6 cylinder & auto have a TCU. Is an exec a V12?

 

morning crystalvision
are you in uk? and if so where?
i have spare coils n bits, if you are not too far away i could lend you a small
package of parts to try out and see if any of them cure the problem
as for the P1621 error code, i have always had that code but my car runs perfect
have allways been told its a nothing code and to ignore it.

oh i also have and x300 exec 6 pot

let me know if i can help

cheers

 

It's a Euro spec car equivalent to our Sovereign or so. It's a trim package for the Euro X300 series that's a step up from the base model but not as fancy as the VDP package.

 

Hi NewQuayMarc

That's a very generous offer I'm in North London though and I think you might be in Cornwall

 

Crystalision..

Did you ever sort this issue out.. Or did you sell the Jag on.. Cause thats exactly my problem!

 

Yes man an end to this post would be great I have a problem just like this one .
Cheers