Zytek Software can run on Modern PC

Just an FYI to anyone running a Zytek ECU car and have access to the diagnostic cable.

Zytec Management software will run on modern PC hardware in a Virtual machine.

Out of necessity I have replaced a vintage 486 laptop with a modern Windows 10 64bit PC running Dos 6.22 in Oracle VirtualBox with a generic USB to serial port converter. Successfully tested on a 1993 Australian Spec XJR-S and a unlocked aftermarket Zytek ECU.

Inquiring minds (especially those with a Zytec ECU) want to know where you get the software, and the diagnostic cable? Can they be duplicated for use by mere mortals?


Jaguar wouldn’t let me take the Diagnostic equipment on a cannonball run so I bought my own cable from Zytek. As for the software, it fell off the back of a truck at the dealership as the car was being prepared for its trip.

Did the cable work without the interface? The little blue box in the Diagnostic Kit for XJ220? Or did you find a means of bypassing the interface? I’m having same problem accessing the Zytek ECU. I have an old laptop with serial port, but no interface. Hopefully I will be getting a cable soon. Any info you can give me on accessing the Zytek ECU much appreciated.

The S80 doc for the facelift XJR-S shows the pinout for diagnostic connector on the Zytec unit. It is a 9 way, round connector, not a standard 25 pin D connector that you would see with a RS232 interface. Only 5 pins are connected, So a regular USB -> serial TTY type cable should have the necessary TX/RX and data handshake if that is what the Zytek unit uses. It isn’t clear from the wiring diagram what the functions of the 5 signal connections are. They are just labelled is input or output with an expected voltage, max being 5V.

Is the magic Zytec cable + interface box just expensive smoke and mirrors designed to make money? Or does it convert a regular serial connection to some Zytec specific command set - knowing if it took power from the harness would be a clue as to whether it was just a passive device, possibly just doing some impedance matching. Some reverse engineering would be easily possible with scope, but dissection would be the know the way for sure.

I have hacked into a few modems and routers by searching for a serial control device on the PCB and looking for what would be a standard UART port. Connecting up a serial lead, after some trial and error on the TX/RX pinout, very often gives me a workable connection. But these are devices given away by ISPs for nothing. Would I try the same hacking on a Zytec ECU that would be a 4 figure sum to replace… :thinking:

The Blue Zytek Box converts rs232 to round connector (in my case i have converted the car to a 5 pin Zytek plug).

The Box does receive power from the ECU. I opened the box many years ago, the board is fully encased in Epoxy. At the very least there is a red LED inside. Without another known working replacement in Australia I will not risk dissecting my interface cable.

’ no consumer serviceable parts inside… warranty void if tamper strip broken’ XJR-S and Xj220 interface boxes are different.

@JAG999: Were you able to get access to the ecu without the interface box? That is the sticking point for xj220 owners. There are literally no interfaces or diagnostic kits (laptop, interface, 2 cables) to be had for love or money. I know the software can run on Dosbox or similar, on a modern pc with emulation.
If you were somehow able to bypass the interface and get your pc to talk to the Zytec unit directly that is a major step ahead. Please let us know.

Also- what is the model or part number of your Zytek ecu? I have a feeling TWR used the same ecu for all the cars and just changed the map on the floppy disk. In that case an interface for the XJ-R should work on an XJ220. My car is in the shop so I can’t get the model # of a Zytek unit in the xj220. Does anyone have one handy that they can look at? Thanks

Whatever the magic interface box is doing, I don’t think it would be difficult to reverse engineer, if you had the components hooked up together, and a scope/data logger tracing the input and output feeds.

I don’t think the XJ220 and XJR-S Zytek units are much alike. A comparison of the two ECUs in the Jaguar parts manuals show two different things. For a start, the XJ220 unit has two separate vacuum feeds for R and L banks, the XJR-S has only one. Since the XJ220 V6 block is based on the rally bred, Metro 6R4 engine, that may be a more fruitful line of enquiry.

Note: The guys who run the XJR-15 Le Mans cars at historic venues, like the Goodwood Festival of Speed, have ditched the Zytek system - more trouble than it is worth.

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One day when these cars are regarded as jewellery rather than just an old race car… there will be someone with deep pockets who will be willing to pay a fortune for those Zytek systems… to return the car to original spec… Look at what has happened to the other Jaguar machines…

Cosmo is correct, the ecus used on the XJ220 and XJS-R are different units. However, the interface may be the same. Waiting to hear back from a colleague. These Zytek units are robust and were (and still are) being used by various race teams all over the world. The only thing I would wish for is a knock sensor. And Godfrey is probably right, people who want originality will return their cars to this system. It’s not that it’s a bad system, it’s that no one has the kit to reprogram it, or clear fault codes if they pop up, except one shop down south, and from what I hear, once dad retired (the 220 guru), they are not producing the quality they used to. Still, if everything is done correctly during the rebuild, there should be no codes or malfunctions. Then the only time you would need the interface box would be to load a new map for better gas mileage:) or, more likely, higher torque and bhp. The default map is for the usual 547 bhp, except on the S cars where it’s 680.

Which is why you go to Don Law…as he has the equipment and the skill to use it… according to my sources there were only 24 sets of the Xj220 Zytek fault finding diagnostic kits manufactured back in 1992 (?) which were sold to the anointed few dealers THEN for 30000GBP each… take it or leave it… if you want to be a Xj220 service dealer… then pony up… all were sent to either UK or EU representative main dealers.( yes I have the list ) I know of only two in private hands… mine and one other… and sorry folks it’s not for sale… or rent! If you are willing to take the risk of damaging a VERY expensive engine… then go play… I for one am not willing to do that to save a few bucks…

Not happy with a certain parts seller in the UK

I’m dearly sorry to hear of your misfortunes… I have had nothing but good service and good relations with Don for many years… Not knowing what may be the basis for the decisions you indicate he is choosing… I’m in no position to comment… The fraternity is too small for there to be ill will amongst us… so please don’t consider my suggestions anything more that what I would wish for you in what I felt would be your best interest… I wish you well in your desire to get the car up and running … and hope we will meet at some point… if there is anything I can help with please don’t hesitate to give me a call… I’ll do my best.

I appreciate your reply, and I do believe you were giving me the best advice you knew about. Until recently I too thought Don Law was THE place to go.

However, his recent actions have alienated a number of people. Let’s face it, our problems with xj220s are ridiculously small compared to the problems around the planet. What my daughter calls “rich white man’s problems”, and I’ve already devoted too much time to what is, in the final analysis, a problem that 99% of the world’s population would love to have. I understand how fortunate I am to be in this position, and am not asking anyone to shed any tears for me. I can always buy another car.

You are correct. It is a small fraternity, and there should be no ill will. There should be help and cooperation between all of us. But I’m not the one who decided to be a bully and extortionist, and this type of behavior sticks in my craw. It is fundamentally unethical. It takes business away from local small business owners (who are not super-wealthy to start with), and it is just wrong.

In my letter to Don Law I have explained the reasoning I used above, and urged him to change his decision and look at other shops as clients for his parts and supplies, not competitors. We will see what happens this week.

I do thank you for the help and advice.

A) Shouldn’t this be on the XJ220 forum?

B) Should this be on the forum at all?

Whuf! Long time since posting.

The diag stuff would be relevant to XJRS owners. Over on the FBook XJRS/TWR owners page we’ve got a running daig going of some XJRS problems and speculation about the boxes/replicating the Zytek interface very much as suggested above.


The RX/TX pins on the XJRS ECM are fairly easy to identify in pub S80 I think. They can ONLY be JSC4-9 and JSC4-6 on the round plug (Pin 10 and pin 29 on the ECM) because all the other wires look like grounds or signal grounds - except for the +12V supply split off to the ECM. The red wire needs to be tested as the diagram makes that one a bit confusing.

Pin 10 on the ECM is IDed as Output Diagnostic Connector 0.670V TX?
And pin 29 is IDed as Input Diagnostic Connector 5V RX?

Admittedly there is something confusing about the diagram as pin 30 is described as 5V Input the same way as pin 29, but if you trace that (red wire to JSC4-3,& 5) the diagram suggest it’s connected to signal ground shield wires - which doesn’t make sense to me.

Either way you’ve got a good idea of what’s TX and RX there.

The next thing that’s needed is some kind person with the interface cable to take an Ohm meter and test the pin-continuity on both sides of the cable so that there’s a diagram for re-making that cable pinout as it connects IN to the interface box.

Duplicating the box is the troublesome bit because they’re unobtainium and stupid expensive. OBDI interface designs of contemporary manufacturers were pretty dead simple though. A few resistors and transistors to invert a signal maybe, or combine RX/TX lines. Maybe a RS232 chip, or a 555 timer. Basic stuff. One can make a mid 90’s GM OBD1 cable with a resistor, diode, and FDTI USB cable.

Maybe if an owner had a buddy at an airport one might be able to examine it via X Ray 3d backscatter teck, or use a CT scanner on it.

The pins could probably be Ohmed w/ little risk to see if there’s a resistor involved…

A modern mid priced oscilloscope could record the RX/TX conversation out of one during a diag session and that would go VERY far in knowing backwards engineering the thing (baud rate / line levels / need to invert signal / if there’s anything that translates a signal in the box (unlikely I think.) Compare inputs and outputs and that should do it. The thing that the box MIGHT do is differentiate between ECMs and communicated differently depending on what it’s plugged into.

Harsher still, and risky, would be to de-pot the thing by putting it in near boiling water and going at any epoxy mechanically (which would usually become rubbery and break away)… but I doubt many box owners are going to allow that to happen.

It would also be nice if both the XJRS and XJ220 floppies could be duplicated via WinImage as *.img files so that access to that SW wasn’t so $$$. Those that still have copies are reasonably interested in getting top dollar for their stuff though. I know of one person who claims to have a floppy (XJ220 & XJRS) set with diag box & cables gathering dust, and I’ll post about that probably on the XJRS & XJ220 facebook pages if the Coventry Foundation isn’t able to obtain them, and if he hasn’t already disposed of them to a new owner.

~Paul Kobres

Paul- these pics look very familiar. If it’s the gent in Ireland then the cables, interface and disks are already gone via a convoluted arrangement with someone else in the UK. But I should be getting a copy of the software for the XJ220, XJR-S, and XJR-15 on a USB stick in the next few weeks. I’m being charged 300 British Pounds ($377) for each USB drive with software, and I will sell the software to anyone who needs it on a USB drive at the same price. No more worrying about corrupt disks.

Now if anyone knows where I can obtain the map for the XJ220S (680bhp) and/or XJ220 “super user” software (not the dealer diagnostic software on the above disks) I’m open to a deal.

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Hi Doc! just so that you are aware… even if you get the system reverse engineered… which from what I am seeing MAY be possible… you might be overlooking one thing… when you receive the information from the diagnostic program… it will come in codes… if you don’t have the corresponding Xj220 technical service manual to decipher the codes… you aren’t going to be able to get anywhere… just FYI.

Can confirm the Interface box for XJ220 and XJRS are the same. Just different software on the PC. There was only one diag kit doing the rounds in Australia.

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