Hello and happy new year!

I have a 1995 XJR ( Swedish, European) and since I bought it two years ago I have had an intermittent no-crank issue, After two years of reading forum articles and countless days in the garage I now think I have at least narrowed it down a bit.

There is no check engine light so the car is definitely immobilized. The "P" is red so it has nothing to do with the gear shifter. There is a new battery and it is fully charged, No fuses are blown.

I recently bought a secondhand "Reader / Exciter" module because I read an article where that did the trick, but made no difference for me. However, I started noticing that the position of the steering wheel had a corresponding effect on whether the car became immobilized or not. This led me to remove the panels around the steering column and have a look at the wiring underneath. I noticed that I could start the engine when I pulled the wiring harness down/ to the right like in the picture I've attached. Now I felt closer to victory, I removed the protective tape around the harness and took a look at the wires, though there was some damage two the wires the only one that was truly bad was the "Wiper fast mode" Cable. After measuring the Resistance of The two red wires from the Ring on the ignition barrel that receives the transponder signal from the key they seemed to be fine, as did the connector between them.

To top it off the "pulling cables" trick does not work anymore and the car is constantly immobilized. So I feel like I am back to square one.

I have looked up a Wiring diagram but I feel out of my depth. Is there any way to find out if the "Immobilier Ring" is sending the "ok" Signal to the Reader/Exciter so I can move further in the system? I have attached a screenshot of the diagram.

Thankful for any help.
Best regards. August


Wiring Diagram http://jagrepair.com/images/AutoRepa.../jagxj1995.pdf

 

Near the area of the reader /exciter ( chip in key transponder ) you have the ignition switch 5 wire bundle with a connector

The ignition switch provides a ground path to car frame ground as a command / enable to the BPM for starter solenoid closing

I found my # 5 pin in the ignition switch connector was corroded

The # 5 pin must also have a good car frame ground that could have been disturbed

# 5 wire will be a black ground

The connector plugs into the car side half on a bracket of the dash and car side half can be unclipped straight up to bring the work out to you

 

try to add keys

if you can’t….fix the wiring properly and then change the transciever coil

 

Hi and thanks for the reply!
I have now checked the ignition switch and the ground going to and from the pin in the connector you showed and that all seems fine and working. Anything else you could think of? Since the check engine light is not illuminating my thinking is that the key transponder signal somehow is not coming through, do you think it could be the Transceiver ring itself or some bigger issue like the BPM?

Since i could make the check engine light come of and on pre-start when i fiddled with the wiring under the steering collum multiples times in a row my feeling is that it has to be a some local issue around that wiring. But everything i've looked at so far seems good?

 

With your supercharged engine you have the different GM tranmission that does not have a rotary position switch like the more common examples on this forum

Pic and editing coming

There are items that must be powered to provide a enable to the BPM so it can provide a command ground to the starter solenoid relay

There are some more things going on in the ignition switch circuit and the 5 wire group that controls the King relays

Editing

I should have your supercharged example on a flash drive

 

Flash drive port acting up

see page 47 only for your example , the other examples are on either side of this page which is not of concern

jagxj1996.pdf (jagrepair.com)

note the note next to the SLCU which must be powered

We are going to be covering the bases to have power on all areas of the car by the ignition switch

this may have something to do with the ignition 5 wire group and the switch or just coincidently something accruing with the king relays as a intermittent issue cropping up

With the key in the run position >>>>>>>>>>>>>>>>>>

All 4 king relays in the corner of the fuse boxes with the exception of the left engine bay fuse box ( runs the car horn ) must click in your fingers going from a closed state back to the open relaxed state

 

If you look to the left side of the BPM these are the enables that must be satisfied in order for the BPM to provide a ground to the starter solenoid relay

So the BPM , Engine ECU , and SLCU must be powered

 

The instrument cluster is powered by a couple of fuses in the left heelboard fuse box

This covers somewhat the no CEL light

 

Thanks for the replies, highly apprecieated. All of the 4 mentioned relays in the fuse boxes do click when turning key to last step. All fuses in the left kickboard are ok (and the rest of the fuses). Still no crank or CEL.

 

the relay's clicking confirms they have the correct command to close but may have burnt power contacts inside

swap the right engine bay fuse box relay with the left to get power to the engine ECU

This same left engine bay fuse box relay can be swapped with the left helboard fuse box for the no CEL light

We're making sure you have power around your car controlled by the 5 wire group ignition switch

When you place your finger on the starter solenoid relay does it click by feel and not by hearing ?

there is a large ECU control relay that will click nearby

this splits the starter circuit in half verifying you have the enables on the left of the BPM in the print

 

The starter solenoid relay power contacts are powered by fuse # 3 / 25X amps left engine bay fuse box which is hot at all times

The control half of the starter solenoid relay is fuse # 12 / 10 amp right engine bay fuse box which is powered by closing the right engine bay fuse box relay ( ignition positive relay )

 

Hi again!
I have now tried switching the left engine bay fuse box relay to the right engine bay and the left backseat relay. No difference there. The Black "starter relay" behind the left headlight does not click when trying to start. I have tried swapping relays there and even sent power through it, the starter engages but engine does not turnover, i guess because fuel is not injected because of the immobiliser system.

 

By not turning over you get no rotation , or do get rotation with no light off firing of the cylinders ?

Gotta ask to be sure

With the large left # 4 starter relay jumpered between the power contact 3 and 5 do you have the key in the run position to have the other relays closed

By the large left # 4 relay not closing naturally with key over to the far start position you are not getting the ground provided by the BPM once it gets all it agreements / enables

Just got up so spooling up awake

Did you jumper the between socket 3 and 5 the large right # 5 ECU controlled relay as this powers the injectors as well as the 2nd power source back into the ECU

On you GM transmission you do not have a rotary position switch in between the starter relay and the BPM

There was a diagram that shows your Key chip transponder wire input into the BPM as a enable but if I recall it is a digital code that can't be tricked so you have to look by elimination the other enables

like in your case the linier position switch which is fragile and gets moisture intrusion is in your sytem as an enable that can be opened and cleaned and tested , This is located to the right of the shift lever box as a large rectangle

Have a good pic from Oliver Marks , if you remove it it can be a pain that Oliver has a thread on

Notice the not in park switch that you see the short pigtail connector

1995 XJR NSS/Linear switch adjustment and not in park switch clean - Jaguar Forums - Jaguar Enthusiasts Forum

in the end what you can test is the ignition switch providing a enable ground through pin 1 to 5 on the ignition switch connector , this will be a spring loaded momentary contact that will waver on you meter so not the most confidence boosting

and the linier position switch without removing on connector pin 1 and 4 as you have the shift lever in the park position , this will be Red / Blue wire to Black

You can see the decoder module / key chip transponder / exciter on page 45 of the normally asperated engine version which is different than yours being it does have a rotory position switch but does not use the linier position switch

jagxj1996.pdf (jagrepair.com)

The I tringle input to the BPM is a descete so we have something there we can test

The BPM is putting out a full B + volts feeling for and seeking a ground path if the encoder is providing an agreement / enable

Gotta run to the hospital for lab and another Doc visit day so won't be back for 5 hours

Ask questions

 

So, today i tested to power the starter by putting a cable between the 3 and 5 slot like you said while my dad turned the key. I hear a sound like something is spinning but the starter does not engage. Which is weird because when I tested this a few months ago i could get the starter going by bridging the relay.

About the Injector Relay. Im not sure how it works, does the ECM turn it on and off and if so Is it safe to give it constant power to test it?

About the linear switch. I have not yet taken a look at the inside however i am getting red light P, N and so on when moving the stick, and I do hear a loud click when going between and wiggling the stick. Can it still be the culprit?

 

You seem to be going off down some rabbit holes that risk introducing new issues.

Let’s go back to the start. You said you had no check engine light. So unless something has changed, that is the issue you need to sort out. Swapping relays, and jumping terminals on relays etc. isn’t going to help.

I’d suggest firstly doing some targeted tests of wiring (given what you said about damaged loom).

Use the Wiring manuals and diagrams.

1. Access the engine ECU connectors. (Right hand footwell, beside A post). With ignition on test the ECU pin PI104-20. This should be Ground when active. If you see Ground on this pin then the car is NOT immobilized. If you see B+ here the car IS immobilised.

2. If you have Ground in test 1 above, then move to the BPM. Do a test on pin FC2-7. This should be Ground also. It’s a direct connection to the ECU pin in test 1. So, if you have Ground at ECU but not at BPM, there is a broken cable between the 2 that needs to be fixed. Do a resistance (not continuity) check between the 2 pins to confirm.

3. If you don’t have Ground at the ECU/BPM, you can try this test. Use a jumper wire to provide a ground to the BPM pin FC2-7. If you do this, turning the key to start should enable cranking. It’s just a test that will prove the other parametes for start are OK.

4. Have you checked fuses and connectors for the Security/Locking module ? (it’s in boot near fuel filler). Remember the key transponder signal goes to the security module and it is that module that provides signal to Engine ECU to set immobilsation.

 

So, today i tested to power the starter by putting a cable between the 3 and 5 slot like you said while my dad turned the key. I hear a sound like something is spinning but the starter does not engage. Which is weird because when I tested this a few months ago i could get the starter going by bridging the relay.

This points to a on the edge starter solenoid attached to the starter motor , full battery charge ? Starter cables tight ?

About the Injector Relay. Im not sure how it works, does the ECM turn it on and off and if so Is it safe to give it constant power to test it?

Yes you can jumper it

The ECU controlled relay is controlled by the ECU and brings power back into the ECU as well as injector powering and 5 or 6 engine sensors and valves

About the linear switch. I have not yet taken a look at the inside however i am getting red light P, N and so on when moving the stick, and I do hear a loud click when going between and wiggling the stick. Can it still be the culprit?

There is some confusion on my part the source of the red park light and it's use in the starter enable , maybe inside a box only so not shown in a wiring guide

So you have 2 switches to show the shift lever park position , the not in park switch and the linier position switch, which is present on all X300 versions , V - 12 , inline 6 and supercharged inline 6

There is the old school of thinking on other cars you must have the red park light for starter enable but how exactly it works on the X300 has not been nailed down in my head

The difference between the not in park switch and the linier position switch is the not in park switch when the shift lever is move laterally will make it causing clicks on the key barrel ( key lock slenoid )

The linier switch is when you move the shift lever fwd and aft past the different P , N, ! , 2 , 3, and D gates

 

Editing , computer keeps messing up on 1st pic , giving it a break , but you see my point

This will be for the supercharged engine / different transmission

 

Hello! Sorry for late reply. I have been waiting for a new used "ingnition key barrel transponder module ring" from England for a while. It has now arrived and as i presumed it made no difference. I am now moving on with your tips. I measured the ohm between the ECU pin and ground, it read 1ohm no change. That should tell me it is indeed immobilized?

I will move on to step three next time i'm in the garage. Any additional tips?

Best regards, August.

 

No I think it shows the opposite, the car is NOT immobilised.

Although 1 ohm is a bit higher than I would expect, the resistance reading will be dependent on the path the current is taking between your test leads.

I think I would try and measure voltage between the pin and a good earth. If you see just a mili volts then I suggest the pin is grounded and therefore in theory the car is not immobilised. So carry on to test 2 and see what you get.

'm suspecting a broken cable is your issue. If that is the case then doing test 3 the car may start?

Good luck.

 

Although the triangle symbol for the Light Green / Black wire does not have a D in it for a digital signal I would suspect the signal is in fact a digital

If you have higher then designed resistance in the wire it would " corrupt " the bits of ones and xeros to being more zeros

Depends on how well the receiver ( BPM ) discerns the signal.

You would have to read your resistance with a 9 volt battery powered meter\\

I have a hearing aid battery powered meter that can give false readings on resistance down a line

Your FC7 connector is one of the large 48 pin connectors in front of the BPM and as the foam inside the climate control air duct joints fails and condensation accurse under the dash it may explain why you measured 1 ohm

I was suprised to see rust going on under the dash on certain brackets

We don't have the key chip transponder ring in the states

But my opinion is they would want it to provide a digital enable to the BPM of a specific code as an enable least it be cheated so the word mobilized and not immobilized would be the term

If you want to get the starter rotating and get some joy it comes down to closing the starter solenoid relay

Editing / Researching