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Did my security module just buy the farm? J-gate is illuminated apparently. The caretaker of my XJR6 while I'm on the road trucking went to start it today and got nothing. The fob lights up green trying to unlock it but the car won't unlock. He had to manually use the key to get in it. Car will not even attempt to start or crank but when the key goes in the ignition the seat and wheel adjust to my driving position so there's that. Also the trunk will not unlock by pushing the button he had to open it with the key. 13.6v on the battery he also tried jumping it. Where is the fuse and relay for the security module?
The fuse for the security module ( SLCM ) is # 3 or 4 in the trunk fuse box and the fuse is hot at all times being directly wired to the battery cable
The key going into the ignition switch makes pin 4 to 5 to car frame ground to trigger the SLCM to ......... Your seat comes alive so somehow the SLCM is also alive
Do not over tighten the positive battery terminal post , breaks the special nut underneath
Never reinstall the battery in backwards < positive post forward in direction of positive direction travel
The important split in half point of the starter circuit is if the starter solenoid relay clicks by putting your finger on it as other relays in the area will click at the same time so you can't use sound
You can swap this relay with the A/ C or headlight
Your starter solenoid relay fuses are # 12 / 10 amp right engine bay fuse box and # 3 / 25 amp left engine bay fuse box
# 12 relies on the ignition positive relay in the corner of the right engine bay fuse box to close , you can swap this one with the left as the left in reality only controls the horn
The # 3 is hot at all times in that left engine bay fuse box
You would have to put your finger on the ignition positive relay to click saying it has the correct close command from the ignition switch ( ignition switch provides a ground )
With the ignition key rotated ro the run position before starting you can remove and reinstall the ignition positive relay and feel it click closed for a single person operation
Last edited by Parker 7; Dec 31, 2021 at 08:48 PM.
I'll forward this to him as I'm 1500 miles away but I think the answer to our problem is in this thread I'll have him go through it, we both have a strong electronics background.
You can tap on the mentioned relays and they will sometimes work
By the relay clicking does not mean the relay is necessarily good , it is getting the correct command , but the power contacts inside can be burnt reducing the current flow to run your device
If the car is a North American model, it does not have a chip in the key using the SLCM
The ignition switch connector is easy to get to and test with the small curved cover under the steering column
The 5 pin is the car frame ground
The 4 pin is the linier key in and out contact which you have been getting being the seat and column moves on key insertion
The 3 pin to 5 is the command to close the ignition positive relay and you really need this to power the engine ECU for starter enable
The 1 pin to 5 is a momentary contact to command the body processor Moule to provide a ground to close the stater solenoid relay on the furthest rotation of the key only
The pic below is of the switch side half of the switch connector about 6 or 9 inches from the switch
This momentary contact Between pin 3 and 5 will waver on your meter so it's not the most confidence building observation
The solenoid is in the square box with the starter in the pic above
You will see this ignition switch on page 39
I will be using a 96 wiring guide as it is better then the 95 as it was put out as an incomplete document as the first models rolled out
The ignition positive relay can be seen on page 37 , there are 2 ignition positive relays on the car but we will focus on this one only in the right engine bay fuse box
More then one pin at a time will have continuity with 5 at the same time and this can be seen in the key rotation table on the top of page 39
The is a 2nd power to the ECU which is controlled by the ECU and brings power back into the ECU , This is the big ECU controlled relay # Right 5 and again it can be felt for clicking and swapped
Fuse # 11 / 20 amp engine bay fuse box ( hot at all times ) and # 6 / 5 amp right engine bay fuse box ( hot at all times )
Your ECU 1st power comes from the ignition positive relay in the right engine bay fuse box and again fuse # 12
You can double click on the image to enlarge and right click to drag around to your area of interest
When I turn the key, the key locks into place as if the vehicle were running. A bunch of lights on the dash shut off but nothing. J-gate is illuminated. Radio and center console ramp all comes on. Fob will not lock or unlock and the left one lights a green light and the right one lights a red light. Fob batteries are showing 3v combined for total 6.02v on my Fluke.
Swapped starter relays, those were fine. The Check Engine Light stays on when turned to crank, the SRS Airbag light shuts off and the rest of the lights shut off
All of the stuff regarding the ignition switch, that still doesn't explain why the fob will not lock and unlock the car. What I think has happened here is the command was given to lock the car and the SLCM hasn't received the unlock command and that is why it is immobilized
This guy had the same problem albeit with a V12 but the symptoms are all the same and his ended up being a Body Processor Module. Mine is doing all the same stuff, wipers don't work and I can't shift it out of park, immobilizer won't work, looks pretty cut and dry to me. I know the V12 and XJR share a lot of DNA so it's definitely worth a shot.
I bought another module and I still had no start. So I dropped it off at a repair shop and we both came to the conclusion that the BPM actually was bad and that I had bought a bad one on eBay. A member here contacted me through PM and sold me a tested module for a very good deal and I had it shipped to the repair shop, they plugged it in today and the car started immediately. Wasn't all for nought, they did find some other wiring issues and did some preventative wiring maintenance and fixed some other small things so the car lives again and it in fact was the Body Processor Module.
Also for the record, the LNA2500AA and LNA2500BB are compatible with each other, the replacement module was a BB out of an XJ6.
I will post this in the other BPM thread for the Google Search Engine to catch anyone else searching this problem.
Key fob doesn't unlock XJR6, no start
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