I have been trying too figure out this issue with my Jaguar.

I have a 2004 Jaguar xj8 and one day it would not start I scanned for codes and I have b1618 transponder module no communication. I take apart the ignition and test the wires and I have no power. So I look at a wiring diagram and it receives power from fuse 26. Which is not blown but has no power.

Cabin fuse 26 gets power from system relay 2. Upon further inspection all fuses powered by this relay has no power and all functions like my vanity mirror lights do not work and my windshield washer pump.

system relay 2 is ground controlled by the rear electronic module from pin 4 cr4 connector the red and white wire I checked and I have no ground I even replaced the module and nothing changed I can see the module is commanding the relay too energize but that pin never grounds. Am I missing something?

 

What are all of the codes your reader sees?

 

As of now the issue is figuring out why system relay 2 never gets its ground. I have also tried too manually ground the relay too no avail nothing happens. According too the wiring diagram and testing with a multimeter the wire that grounds system relay 2 goes from the rear electronic module. I replaced the rear electronic module and that did not fix the issue according to a couple other people on this forums it seems as though that relay is known too fail and a couple others have reported they’ve had too replace there passenger fuse box. I ordered one from eBay for $30 it should arrive on the 4 of the December here’s praying that fixes it and I can change my name too WorkingXJ8.

the cart has no other known codes. I bought this car a month ago from some guy it needed 4 new air struts and a steering rack. The car ran perfectly fine when I went and looked at it and a whole week later when I came back with a tow truck and the $800 cash me and him agreed upon the car is a little rough but only has 99320 miles on it. I do the air struts and the rack go too start the car too get the power steering rack bled and it doesn’t start. Won’t even crank. I scan the car and it has a code that the transceiver module for the ignition chip is not communicating. I bought one replaced it and that didn’t fix it. Should have diagnosed it instead of throwing parts at it. So I hook up my multi meter and I see there is no power going too the power wire for the transceiver module according to Jaguar, this module receives power from fuse 24 not fuse 26 like I stated before in the cabin fuse box. I pull the fuse and it’s perfectly fine I hook up my multimeter and I am getting no power fuse 24. The wiring diagram shows there is a relay that contains two relays soldered on the pcb board of the fuse box. System relay 2 is not energized everything that operates on that relay does not function in my car. From my washer pump, vanity mirrors my left blinkers and my transponder transceiver module all operate on this circuit. The car was not like this when I picked it up which baffles me because I’ve only had the car start once since it started doing this so the issue must be intermittent and afterwards when it does start it acts like everything is normal no lights engine runs fine and it starts immediately. Doesn’t cut out and everything stays working even if I shut it off and try too start it again it isn’t until I walk away and come back after a while that it will act up

 

I also know someone has been in my passenger footwell before most likely looking at this fuse box I know that because there was this flashlight under my carpet

 

You cannot diagnose items individually on this vehicle! All systems are interconnected. A PATS fault will stop that relay from operating for many reasons. Did you try a second key?

 

I have no second key. The key works fine the transceiver ring never gets power. But that doesn’t make sense cause that relay also controls other unrelated functions like the vanity mirrors and the washer pump. They wouldn’t design it where the relay that supply’s power too the transceiver ring never energizes if the key doesn’t match. The anti theft being wonky is not a cause for the relay too not be functioning it’s an effect. If I run a wire directly from power too the transceiver module bypassing the relay completely the car will start everytime. That relay never energizes even if it’s manually grounded.

The transceiver ring has been replaced no change. The rear electronic module has been replaced no change. Now I am changing the fuse box. I feel as it’s the relay cause even if the relay is manually grounded nothing happens. If that doesn’t fix it I am gonna Frankenstein it and just run direct power too all of those functions that relay supplies. System relay 1 and system relay 2 are supposed too cycle anytime the car is woken up or goes too sleep. System relay 2 never does.