I was thinking I should read this thread again from the beginning, to see if I’ve missed any clues. But alas, I’m already 57 and am not sure I could finish such a task, considering the life expectancy for a man my age.

One quick thought: Have you checked all fuses, not just the ones previously mentioned? Might not hurt to spend 20 minutes or and just check ‘em all.

A blown fuse could be the secret behind so many faults at once. Not 100% sure how bus faults are logged, but it’s possible a simple loss of power to one module can cause the others to report this as an ominous loss of communication.

Won’t cost anything to try but a little bit of your time. Rather than just a visual inspection, rig up a test lamp set-up to check each fuse. It’s rare, but sometimes when a fuse blows, it is not always obvious when looking.

 

I found a few replacement fuses with a free testing unity that probs the top pins and lights a small LED. Everything is fine.

I am doing research now and found a few more PATS 24 cases in Jaguar and even stumbled on a fault 2-4 (same thing). They all lead to the immobilizer and PCM harness or general damage.

I'm guessing the VVT solenoid burnt a pin and or there's something I can repair once inside. I'm even more confident of that now and willing to buy the tools to remove it and take a look. One gentleman very easily applied some flux and used a heat gun to remove the memory and swap it into a new ECM unit and so I watched another related video and feel like it's another possibility. If using my spare to swap out fried pins or parts doesn't do the trick I can always pull the IC chips.

"Original ECU had some issues so second hand unit was acquired however had different part numbers - however the main circuit board was identical so swapped over main Micro controller and 2 memory ICs - This was the procedure that followed"


This new information may at least give us closure on the steps taken and in addition, provide an idea of where we are to go from here.

PATS 24
https://www.jaguarforums.com/forum/s...d-67311/page4/

 

Also, via the "general approach to circuit testing" guide, we should be at the solenoid (consumer) doing a split-half test to determine if it's on the power side or ground side. In this case it is controlled by the ground side directly by the computer. I wonder if a resistance test would diagnose a failed connection here as it did with the last test to the CANbus link.

 

Are you talking about a little doohickey that tests the fuses while installed? I'm not sure I'd trust such a device. I'd want to pull each fuse to be 100% sure I wasn't somehow getting a false reading through the rest of the circuit.

I should have mentioned this earlier, but by physically pulling each fuse, you can inspect the prongs for discoloration caused by overheating. We've had a few cases in the forum of loose sockets for fuses and relays. When this happens, you get arcing and high resistance, without necessarily blowing the fuse. I get it, inspecting each fuse seems like overkill, but this situation is off in uncharted waters. It wouldn't hurt to check the relays for discolored prongs, too.

Also, did you check at the primary junction box? I had owned my car for several years before even knowing about this panel. It's inside the cabin, just outboard of the US front passenger's feet.

 

When you feel the tranquilizer dart make contact, just relax. Don't pull it out. And drop the soldering iron. It's for your own good:




I realize we can't stop you from looking inside the ECM. But swapping internal components? Several of these modules have VIN-specific security info loaded with the software. Start swapping memory chips and odds are very high you'll be making a very nice paperweight that can't be reprogrammed.

 

"I realize we can't stop you from looking inside the ECM. But swapping internal components? Several of these modules have VIN-specific security info loaded with the software. Start swapping memory chips and odds are very high you'll be making a very nice paperweight that can't be reprogrammed."

ECU IC Swap Over Microcontroller/ memory

Where does the VIN live if not in memory? The brain of the computer doesn't store information and is just a processor...

I really think probably just nuked a pin considering it's a grounding post that suddenly turned hot when I send a charge through it. If there's another resistor in there I can more easily swap it out and in the rare and final case I do an ECU IC Swap and if that fails I pay someone to use the (still good) parts and put it together again. There's not water ingress or anything like that and it is isolated at the bottom of the ECU for a reason (straight grounding connector to solenoid).

I'll do many more hours or research and research questions but I wouldn't assume the VIN specific information can't be kept with a refurbished original, or even the IC swap method in the rare case the board or pins can't be easily fixed with a quick replacement part. All some boards need is a reflow using the flux and head gun and they chirp back up... I wouldn't send this to someone to fix before having a good look at it and at least trying to do an easy repair myself.

I'm not casting out the other steps involving the multimeter and testing fuses, just because I disagree on the assumptions above and we have a little way to go before we can pull the ECM but we're getting close.

Is there a resistance between the VVT solenoid and ECM that changes if that pin is lost? Would it change anything with ground switching? The code 24 suggests fuses are not at play and it is a communication issue between the PCM and dash console and so if it's not either of the two potential units that can go bad there and we have 600 ohms... it leaves only one piece left in the loop? If the computer had full functionality we would get some other error IMO. It's not even responsive enough to tell us it's broken and nobody is home.

I don't see why they couldn't just throw an inline wiring fuse in here but I guess when it's ground switched it relies on very small differences in the charge to determine timing and nothing can really go between... I assume it's one of those things were "when you do this it blows the ECM" but they try to stick it at the bottom and away from other major components so that it can be easily isolated and the ECM restored to proper working order. Unless there's a ECM to ground connector that can burn out therefore disengaging the ECM unit. I'll continue to look for alternative stories, naturally.

I checked the junction box and pulled the ones that were most pertinent or anything related to ignition, EMS etc.

"A fuse usually won't blow if you have a short to ground on the control wire of ground switched circuit, for example the control wire of an injector or ground switched relay this because the curent has to pass through the load ressistance before it shorts to ground." -Scanner Danner book questions and discussions

Load resistance is the PCM which rests between the ground switching cable and ground and if anything is damaged that resistance should be changed... I'm just not sure to what degree of measurement. Maybe it will be broken vs a grounding connection...

 

"A fuse will blow if it experiences current flow greater than its rating. So, if a short occurs causing excessive current to be experienced by fuse it will blow.

Let us assume a simple switched load circuit (ground side switched/pull down circuit),
power source -1> fuse -2> load -3> switch -4> ground

Some scenarios:

If somewhere in 1 there is a short to ground, you got big problems since there is no protection for the battery and wires. This will have full battery current to flow to ground, really, really bad.... The wires would melt and maybe cause a fire due to the amount of heat caused by this condition. This is why fuses are usually very close to the battery/power source.

If somewhere in 2 there is a short to ground, you will blow the fuse. Why? There is no load between power source and ground. Therefore max battery current will flow to ground causing the fuse to blow, but in a safe manner. No fires. Just that the fuse would keep blowing when replaced.

If somewhere in 3 there is a short, the load will stay on, regardless of switch state(on/off). And the fuse would not blow. What?? Why? Because there is a load between voltage source and ground. Think of it this way. Is there a difference between this ground/short and the switch providing ground? Nope.

If somewhere in 4 there is a short, you might not notice anything unless the ground isn't very good. The switch would control the load, and the circuit behavior would probably be good.

I have simply explained this so with simple explanations some details are left out. But the moral of the story is that you need exceeding current flow of the fuse to cause it to blow. So, it depends where the short to ground is, before or after the load.

In addition, some of your confusion is caused by the type of circuit you are dealing with, ground side switched or power side switch. Again, these circuit only differ on the location of the switch/control (before or after the load).

And yes, when debugging a circuit, I always verify common components that fail before assuming the world has ended, resulting in me having to take the car apart. LOL. So, I check fuses, relays, switches, loads, .... first.

I hope this helped."

I am guessing we are ground switched and at point 3 and it is doing code 24 now and even after replacement of solenoid. The load is the solenoid and the switch is the PCM..

"A short, whether to ground or to power, is an electrical contact outside of the designed circuit. A short to ground is where a circuit has made contact to ground outside of it's designed path. I.e. a control wire rubbing on an exhaust manifold bolt. This is not an open circuit failure. There is still current flow in this circuit, but it is not going through the normal path to ground, or through whatever control device is there to control it."


This post will need a full summary for future readers. But I enjoy going through some of it and the process. Some day I'll get to enjoy the Jag with 30% more horsepower from VVT timing to the computer that will unleash all of the little enhancements to oil, exhaust and air/fuel for the supercharged V8.

 

I called a very helpful local mechanic and politely asked for advice to get the car moving again and he said there were youtube videos and ways to test the wires and that could be why it was unplugged. A short to ground or something in that connection would mean it would heat up and cause issues. I should check resistance for each wire etc. using a wiring diagram. I have yet to find these videos but think they must exist. If we have a guru that knows about wiring and resistance feel free to chip in for a shot at the fix.

 

[QUOTE=DrJagerCola;2170527. If we have a guru that knows about wiring and resistance feel free to chip in for a shot at the fix.[/QUOTE]

I'm going to go out on a limb and suggest that kr98664 could be your man.

 

Absolutely!!

 

I stopped there because the rest is mostly garbage. You seem to be assuming things that just are not so. You're going to carry on spending a huge amount of time and brain power it seems to me, but getting nowhere apart from more and more confused and more dead ends.

 

Various of the critical items live in several modules and the car goes to anti-theft lock-out if you mess with them wrongly.

You definitely need IDS/SDD and knowledge at that point.

 

When I said

Note: you can generally short out any of the sensors to ground or battery + and just get a code. The PCM survives fine.

It is meant to be the same as

Note: you can generally short out to ground or battery + any of the sensors and just get a code. The PCM survives fine.

 

Okay, you're clearly dead set on your answer but don't see where upstream past the first 10A fuse damage could be inflicted. The very first relay is the EMS and it's fine. There's nowhere left.

While I agree that the VIN is matched to the modules, none of the modules live in the ECM per se. They live in the trunk for ABS or under the hood and have their own memories of the VIN and so fixing the PCM would not change their minds.

Why don't you see the logic in breaking it down into 1 Battery.... 5 ECM and explain what happens at each stage? Sending battery power to the PCM grounding wire on the non switched side offers no resistance or fuse to it's source. Where's the logic in denying some sort of damage?

 

I'm done.

 

Thanks for your help and have a Merry Christmas!

Unfortunately, this is my post and so I can't just walk away when someone annoys me and so I'm happy we're past it and I gained a lot of valuable insight about the battery and still believe you know something about the vehicle and the way the PCM is built and works. I'm not sure you were able to share that but it sounds like you didn't want to.

I hope others will continue to investigate and trouble shoot fact and reason with me and I'll continue to assume some want a resolution to PATS 24 and in general the possibility of a battery, fuse or ECM fault. Once you take emotion out of it, that's where we share a common goal.

Unless someone has a better argument against the way the electrical system generally works with a closed ground switching system plugged into the ECM, we're going back to testing the resistance and voltage at the solenoid and working toward the PCM as a possible culprit. No offense, it's just a precarious position to be in but that's where we're at.

 

As I read your many many posts you are absolutely determined to do things in your own way, so I am out of trying to guide you to consider what I see as the relevant and quicker way.

 

What have I ever done to you?

 

Well..We've lost JagV8. We might be about to lose Karl.

This thread is entirely to long to expect one of the Jaguar Master Tech's to even read. I've tried to keep up but it gets off the track several times.

If we know that the battery is not the issue...We need to start with determining what possibly IS the issue.

When you stick your key in the ignition..does the light on the dash automatically flash the "24" code? The IC and the PCM share in how the PATS system works. We can tell you've done a ton of reading and research.

http://www.jagrepair.com/images/TSB/...t%20System.pdf

This Link which I'm sure you've read shows that the security system for the vehicle is indeed stored in the PCM. Whether or not..If you feel you need to replace of repair the entire PCM or simply a component on the board..we mere mortals might not have access to the engineering information to determine which integrated circuit actually contains the PATS check information.

I guess if you feel froggy..Pull the PCM out and check for burn marks on the board.

 

This particular instance of non-start does needs a summary and outline.

I'm new to forums and I'm not sure if it's possible but for those that find the thread by keyword I can sum it up on the first page for them.