Hello to all, I would like to ask for some help but first I will give the details of this vehicle. It is a 1997 Jaguar Sovereign (X300 ROW, w/ immobilizer) with a 3.2L in-line six, left-hand drive, and an automatic transmission. I came up with the details from searching the internet for information basing on the vehicle's VIN (SAJJHAMG4BPxxxxxx) but if I made a mistake, please let me know. The problem started when this vehicle was taken to a paint shop to have it re-painted. The owner of the paint shop informed me that after the paint job and washing of the vehicle, it would not start, not even crank. They checked the battery and the fuses and found them to be OK. They soon discovered that the engine ECU was wet with water and so they dried it up but still it would not crank. Basing on the information that they gave me, I removed the ECU and checked the connectors for water corrosion but there was none.

I opened the ECU and found it to be very clean with no signs of water damage. So I connected a scan tool to check for DTCs but the engine module did not show up. I checked the wiring from the ECU to the DLC and it was OK. There were no signs of wiring damage in the entire vehicle. I am now leaning towards a faulty ECU, but I still needed to do more tests.

I then checked out the wiring diagram from the service manual and did some voltage checks on the ECU (IG ON to P1105 terminal 33; ECM Control Relay O/P from P1104 terminal 18; ECM Control Relay Supply to P1104 terminal 24) and they were also OK. I also checked the Ground connections to P1104 terminals 1, 12, and 36 and they were also OK.

I also found out that the engine does not directly control the starter, it is the Body Processor Unit that does. Upon careful studying of the wiring diagrams, I found out that the BPU needs to see the Check Engine signal for it to allow the starter to crank. So I isolated this terminal and connected a jumper wire from this terminal to body ground. I was able to crank the engine this time but the engine won't run. The engine needs the data stream from the immobilizer module to release the fuel injection system. I scoped the two wires from the coil on the key barrel and I got some kind of an "inconsistent" waveform (as compared to one from an E46 BMW).

Right now I am heavily leaning towards a defective engine ECU so I need to know if just replacing the ECU with a matching Security ECU will be enough. Or will I need to have a matching BPM too.

Please help me out.

 

On another note, is it possible to replace this with an engine ECU that has no immobilizer function? I have attached photos of the actual ECUs in the vehicle

 

razirafi,

I've moved your question from General Tech Help to X300 forum. Members here with the same model will be able to help.

Graham

 

My apologies for not posting in the correct section. Thank you.

 

Well it certainly sounds like your ECM is fried. Might be difficult in the Philippines but if you can get hold of another ECM to test that would be best.

Does your car have 4 O2 sensors or just 2? That would make a difference in what kind of ECM you could use. Also not sure if you would need another SLCM as I believe it provides the immobilizer status?

 

This particular Jag has only 2 O2 sensors and yes it will be difficult to get a hold of another Jaguar ECU here in my province, but I can get one from online sources, I just need to know if I will need another BPM or a BPM + SLCM. I checked again the electrical wiring diagram and found that the immobilizer only sends a locked/unlocked status signal to the BPM, which I think is only for the doors, windows, etc. I don't think that this signal has anything to do with the fuel injection. On the other hand, the signal from the immobilizer to the engine ECU is the one that releases the fuel injection system, allowing the engine to run or not.

My thoughts: If I use an ECU that has no immobilizer function, then I may be able to run the engine because in this case the fuel injection system is already released (from the factory). Problem now will be VIN matching of the major control modules in the vehicle if VIN matching is designed into the system (allowing the vehicle to run or not). Any thoughts on this from the Jaguar specialists?

 

There is no matching between BPM and ECU and SLCM. All units are independent of each other. There are lots of threads where people have swapped out the engine ECU (usually as a result of bad advice from a mechanic), and I personally have swapped a BPM on my car.

It sounds as though you know what you are doing and have done some excellent diagnostics already so at the risk of being patronizing can I just ask if you have checked the inertia switch has not been triggered?

 

@b1mcp: Thank you for that information, and no, I haven't checked the inertia switch. I will have a look into that and I will post back. Thanks again.

 

...been busy with another vehicle the past week. I have checked the inertia switch and it has not been activated. To make sure, I checked the wiring diagram again and saw that power from the battery goes to the inertia switch, which in turn supplies power to the heel board fuse boxes. I have power to both heel board boxes.

Regarding the replacement of the engine ECU, what do I need to match (aside from the basic part numbers) for it to be compatible with the vehicle? The original ECU's part number label reads:

3.2L N/A
LNB 1410 BB/2--

GEMS 6 CONTROL UNIT
Type Code AA/2--

 

I am suffering from the same problem as you are.
What bothers me is that you do not have a label from PECUS, at least on the picture, on which is written the two numbers after 2 (2XX).
It appears that if you find an ECU matching the last digits from the PECUS lable, that car should run without any problems.
Take a look at this article, if you have not done it yet, it may be helpful:
Jaguar XJ6; Jaguar X300; Engine Control Unit; ECU

 

Ah yes, I have already read that one (but thanks for the heads up). I have also referenced this one https://www.jaguarforums.com/forum/x...cu-x300-95451/

I am thinking about this one: for a matched pair of engine ECU and SLCM, the SLCM sends coded data to the engine ECU to release the fuel injection system. What I do not know is if this coded data is specific to the matched pair or is it a "generic" data that any engine ECU can read and thus release the fuel injection system. I have found this (JAGUAR X300 3.2 XJ6 GEMS 6 ECU CONTROL UNIT SAGEM-LUCAS LNB1410BB | eBay) and it matches perfectly aside from the Date Code

 

I think the latter the year is, the better it will be.
I have seen that some sellers offer the ECU, reader and the key together, so may be they have something in common.
If you have bit for the ECU, hope it will work for you, may be I'll try with different suffix

 

To the OP. Have you checked the inertia switch in the passanger footwell? If they bumped the car hard for some reason the switch may have tripped and disabled the starting sytem.

 

@Urchins: Yes, I have seen some listings that included the barrel and key, the reader module, and the engine ECU. Since there is no PECUS label, I think I may go for the one with the 211 suffix, as this vehicle has an auto tranny. On a side note, I am not new to this sort of thing as I have done ECU swaps on other makes of vehicles using ECUs purchased online, the latest of which is a MRSZ5 module for an E90 BMW. After installing the module, lots of errors showed up in ISID, with the most significant one being "coding does not match". I merely recoded it with ISID and all was OK. The thing that is holding me back on this Jag is my lack of information on what I need to look out for. I know that I have been shared a lot of information already but I still feel that I need more, especially regarding the immo function (coded binary stream between a matched pair? or does the SLCM simply supply a ground signal to the engine ECU's fuel injection inhibit pin to release the fuel injection system?).


@ls99: Yes, I have checked the inertia switch and I have power going into the heel board fuses. Please let me know if I have not done something that needs to be done or checked.

 

I think you are over estimating the sophistication of the X300 electronics. Don't forget this model is 20 years old now.

I have Jaguar IDS system and have used it to re-program X Type ECUs amongst other things in the past. As far as I know there are no options for re-programming or re-loading the ECU for the X300, or for matching the ECU and any other component.

The ECU should just be plug and play as long as you get the right part. As an example of a thread where an ECU was replaced without any other coding see here

https://www.jaguarforums.com/forum/x...-rough-107302/

Hope this gives you confidence to go ahead

 

@b1mcp: yes, you may be right, and I may also have been too critical on the complexity of this 20-year old car's electronics systems (because I am a newbie to Jags). Anyway, I do recall that you informed me that there is no matching between the different ECUs and that they are independent of each other so OK, I will read up some more, try to look for the best match that I can source, and do what I need to do.

Thank you for the confidence boost.

 

I am not sure of exactly what is or isnt lighting on the dash. However.... if the shift interlock is stuck the car will light up (at least i think it will) but will not crank. If a body shop is not familiar with the shift gate they may have stumbled into or out of park in a weird manner. If you havent tried it yet. I would use the key to actuate the plunger if needed and shift the car through the gate and back to park firmly and try to start the car. My apologies if I missed somewhere where this doesnt fit your symptoms or you have tested this. It would be nice for you if havent. It certainly faked me out last week.

 

@swaschka: well, practically all lights on the instrument cluster comes on during the POST, and then some go out after a few seconds. when I switch to Start, the SRS light comes on, and off when I release the key. I have also tried shifting into all positions on the shift gate and the corresponding lights come on. If I don't step on the brake pedal it won't release from Park. I think the shifter is OK. but there is no harm in trying out what you are suggesting, thanks.

 

If when you step on the brake the shift releases then the interlock feature is working in that capacity. The question would be how does the car know to immobilize based on the shift position. And can you trick or check that similar to how you did the chk eng light value. It would probably be a switch of some kind to replace which would be cheaper than an ecu. But this testing is beyond my rule of "Its something stupid" At the dealership (many years ago) if you missed something stupid you lived with it like a badge for a very long time.

Last week i went to the grocery store. I was just bragging that the car had a lot of issues when I bought it but they've all been fairly simple issues. I put the key in switch to on, let the car do all its stuff, twist to start, nothing. Did that a few times. Felt that quick pit of the gut realization that it is a british vehicle. And for what ever reason checked the shifter. Hopefully the "its something stupid rule". It was in park. Moved it back and forth, tried to start, nothing. Moved it back and forth again and gave it a few nicely firm jabs into park tried it and it started. So I dont know. I just find that often times we have conditioned ourselves so much to accept the worst that we overlook really stupid stuff. We are conditioned to be ok with an ecu failure. And it certainly happens. But so unlikely that you take a working vehicle to get painted and the ecu dies. I dont know anything about the x300 ecu yet. But water intrusion would take a fairly reckless soaking for most to fail. Sorry just hoping for you. And if you subscribe to this theory already.... dont mind me carry on. Oh and my wife's ML plagued us with many bouts of this a year or two ago. Several trips by me to retrieve the truck for her went by before i realized it was a multifunction plastic brake switch. Sorry just remembered that.

 

yes, I think I know what you mean...sometimes it is the really simple (and stupid) things that we tend to overlook which is causing problems. I will check into this very carefully. Thank you.