Hello all I need a pin out and polarity diagram for the Denso COP unit on my S-Type. Coil Number 2W93-12A366-AB I am trying to build a tester for this but I can not seem to find a reference for the pin out and trigger voltage or polarity of trigger.
Any help would be great.

Can't help with the coil specifics, but vehicle wiring diagrams can be found at the top of this page:

JagRepair.com - Jaguar Repair Information Resource


Can't see all the details (on my phone), but IIRC the coils are supplied with constant battery power and a switched ground.

thank you very much for the reply. I will give that a look. The thing that’s got me confused that there is four wires. And according to most “pinout “there should be a 12 V constant power, a ground, and some kind of trigger… With either a second ground on wire 4 or a feedback loop going back to the ECU.

OK, so from what I can discern from the manual you provided. PIN one red white is power 12volt . PIN 2 appears to be some kind of input to the ECU. PIN.3 black appears to be ground. And PIN 4 if I’m reading this correctly is the trigger input from the ECU. I’m tying to design a DIY coil tester that I’ve seen posted on YouTube etc. to hopefully try to track down why this thing started missing so bad.

The coil units are a known failure point in the ignition system; it's best to replace them as a set.

What are the LTFTs and STFTs?

Have the spark plugs been replaced?

Keep the old ones in case the new aren't what they should be.

spark plugs were replaced about 2000 miles ago along with aftermarket coil packs, sadly because I can’t afford original ones. Which is exactly why I want to build a coil checker and see if something is screwed up. I don’t own a scan tool. So I can’t tell you anything about fuel trims.

You can buy an elm327 that's good enough for fuel trims for $5 or so.

COP checkers can be bought and I suspect work adequately.

Ah, some more details coming to light.

On the forum, we've had members learn the hard way about aftermarket coils. They just don't hold up, and often fail quickly. Some are bad right out of the box. You don't necessarily have to purchase official Jaguar parts in their jewel-encrusted little boxes. I've had excellent results with QUALITY name brand parts such as Denso, NGK, Motorcraft, etc. I forget all the details, but I think Denso was the OEM supplier for the coils. I'm sure somebody will jump in if I am less correct than usual. But definitely stay away from aftermarket brands like Fling Dung or Wok Hoam. Some of the worst seem to be the no name specials on eBay. I'd even suggest avoiding the house brand from discount chains if shopping locally.

Normally I'm all for testing suspect parts whenever possible. The coil tester idea sounds pretty slick. Heck, I've built all sorts of single use test equipment, littering the back drawers of my tool chest. But with el cheapo aftermarket coil packs installed, I'd simply replace 'em. I'm cheap as can be, but that's one place not to skimp.

If you're really intent on testing the coils, you can still use the engine itself as the test bed. No scanner? You're working blind on 1996+ vehicle. You don't even need the fanciest version. I've got a simple OBD II doohickey that talks to my phone via Bluetooth. Maybe $50? I've had it for several years. With a half decent scanner, you can retrieve fault codes pointing to specific cylinders. Make note of the location and swap the suspect coils with another location that's not faulting. If the fault code changes to the new cylinder, you know the coil was bad. For what you might spend building a coil tester, you can obtain the same pass/fail info using a simple scanner.

Attached a workshop page of the diagram with some names, if you are in need of something more specific I can try to find it. Not sure the best way to bench test them, I would suggest a Picoscope with the inductive pickup on a running engine, you can graph them all against each other, but this is not common or cheap tooling.

This is basically the triggering circuit used to pulse the coil. I didn’t exactly have the correct resistors so I’m gonna guess It’s as close as I could make it.
Well, I built a device and it seems to be working OK. I had it on a bread board and it was hit and miss but after I actually built the circuit on a board, it seems to work quite nicely.

Well, I was able to use the tool and I definitely found two for sure bad coils and one that had this weird spark… So I replaced all of those. The engine runs better. It doesn’t seem like it’s loping so bad still has an intermittent miss someplace, but it’s nowhere near as bad as it was before I can actually drive it. I also sprayed some mass airflow sensor cleaner down inside the mass airflow sensor. Somebody told me that could possibly cause rough idle. I have a sneaky suspicion. I have a failing O2 sensor, although I’m not exactly sure how they’re supposed to read. I connected it to a scan that my friend owns and one of the sensors doesn’t really do much.

What DTCs did your friend's scan tool bring up?

That’s pretty much the gist of it. Photos might be kind of crappy they were taken as a screenshot from my phone.

You have 25% STFT, and 19% LT, which means your PCM is adding 40% more fuel to compensate for data received from the O2 sensors. You also have a fairly low MAF value (rough average of 1g/s/L at idle on most cars), and O2 response codes, pending air metering codes. This reads like a vacuum leak at idle. Smoke test the intake or use some other method to find where the added air is coming in. Can be anywhere after the MAF.

I am going to ask him again to rescan it after I fixed the faulty coils, etc. Someone else mentioned at one time that these 4.2 L engines are notorious for intake. Vacuum leaks as it’s basically a three-piece intake… And of course, plastic. But we sprayed carburetor cleaner everywhere And couldn’t get the RPMs to change consistently. I will post back as soon as I get the new scan results. I will clear the existing codes. Take it for a drive and have him scan it again. Thank you very much for replying to my thread. I feel I’m on quite a large learning curve lol the only other newest vehicle I have is a 92 Chevy pick up. And that has a carburetor on it lol

I wouldn't use RPM change. Watch STFTs as you spray.

100%, this is the best way to do it. Watch the trims live, any added fuel should be very noticeable on the trims as it gets pulled in.

Here's a good primer on using fuel trims to check for vacuum leaks:

JagRepair.com - Jaguar Repair Information Resource


You have to think differently when troubleshooting a computer controlled vehicle. The computer will try to maintain a steady idle speed. On older vehicles, spraying extra fuel across a vacuum leak would change the idle speed. With a computer, only the short term fuel trim will change and the speed stays constant.

One caveat: I prefer ordinary starting fluid for such a test. It's cheap and very effective. Some guys will use brake cleaner but some modern eco-friendly formulations are not very flammable, if at all. You could hit the vacuum leak but since it's not readily combustible, the fuel trim won't respond.

Before getting too deep in chasing vacuum leaks, I'd get those misfire codes sorted out. If misfires are still occurring, the poor computer may be making other changes to compensate. Always make sure the known problems (misfires in this case) are corrected before digging elsewhere.