Greetings all,
I am afraid this is another "no start" thread. I have all the common symptoms with my 1998 xjr:

• engine fault
• trans fault
• abs/asc fault
• incorrect part fitted
• and so on

The symptoms are that not only will the car not start, but it appears to be dead even at pos 2 on the ignition. Fuel pumps don't prime, throttle motor not energised, AC unit & fans do not come on, J-gate stuck in park & not illuminated, no click from brake switch & also the dash does not light up with the system check lamps. The only thing that lights up are the two indicator arrows & the blue main beam lamp.
This problem used to be intermittent i.e. if I leave the key in the ignition on pos 2 for a few minutes, suddenly it would spring to life (electronically speaking) and be able to start. But now it seems to be permanently dead!

The things I have checked so far are:

• Battery - substituted for known good battery - no change
• All the main power dist relays substituted for known good relay - no change
• Fuses checked, but only by visual inspection
• Main power dist studs all checked - 12 v at each one
• J GATE illumination module removed and visually checked - no obvious signs of burnout or bad connection
• Inertia switch not tripped
• Ignition barrel transponder coil replaced with new.
• Spare key - also does not work

What I have not done yet is go through the car doing multimeter tests. Before I invest time on this, I was hoping I could eliminate the key itself as the problem. So the test I thought valid would be to open the car window, shut car and lock it with the fob, then reach through window to activate the alarm, try to cancel alarm by putitng key in igntion anf turning to pos2. Can anyone tell me if this is a valid test? If not does anyone know a way I can eliminate the key & the KTM as a possbility?

Thanks in advance.

 

I think the KTM only comes into play when you're going to start the car? I'm not 100% sure on that though.

Is there a difference in anything between key pos 1 and pos 2? Then it's probably not the ignition switch.

Do you have the workshop manual and electrical guide for your year? Multimeter tests will save you a lot of time if you approach things logically, breaking down by subsystem. Get familiar with the power distribution schematics, and the ignition switched ground (sections 1 and 2), start at top most level first. Check battery connections, and the high power fuse. Check that the fuse boxes that are direct to 12v are indeed at 12v. Switch key to pos 1, make sure the correct fuse box(es) is now at 12v. Switch key to pos 2, same thing. If you see an entire fuse box that's not powered on, there's your culprit. If there's no fault there, move on to checking voltage levels at each fuse.

Another very simple check, before getting to that, check that both connections at the gauge cluster are fully seated. Disconnect and reconnect them to be sure. These can cause a lot of problems if they're not secure, and they don't always sit in tight. Make sure to disconnect battery for at least 1 min before doing this, to be safe.

 

Sounds like the ECM fusebox in the engine compartment is DEAD.
Try replacing the relay in the fusebox or 'jump' the relay 30/87 connection to se if the ECM comes to life?

 

Take a look on the fuse box under the hood

 

Thanks for the help with this.

At position 1 nothing lights up, but this at least cancels the alarm. At position 2 some lights come on the dash and the message screen states startup checks - although the CEL, brake check lamp etc do not come on. All auxiliary stuff works eg. Windows, horn lights, seats etc. AC does not come on.

I have checked volts at the ems relay pins: 12 v on pin 2 0v pin 1, 12 v on pin 3. Ign pos relay is 12 v pin 1, 0v pin 2, 12 v pin 3. In the control module relay box, all relays read 0v pin 1 & 2 & 12 v pin 3. (all with key in pos 2 btw).
Also canbuss checks are good, i have 60 ohms between pin 6 & 14. Voltage check was dodgy though, with the ign on I measured only 1.3v between pin 14 to ground & 2.3v pin 6 to ground.

 

I should make a correction here: the ign + relay has 12 v on pin 2, 0v on pin 1.

I am not making any progress with this. I still cant rule out the key itself , but the instrument cluster is suspicious - why do the "battery check", "brake check" and "CE" lamps not illuminate during the start-up checks? Or is this just a symptom of immobilisation due to the key not being recognised? If the IC is fried, would that not show up by performing a resistance test on the CAN bus?

 

Ok I found the problem.

The symptoms I described are classic symptoms for the inertia switch being tripped (as stated in a trouble shooting PDF found on this forum). Although I checked the inertia switch several times, I never thought to disconnect it. Live data from the BPM was showing the inertia switch to be at "1" i.e. off in Jag logic, so I decided to disconnect it, to see what effect that had. So it transpires that the cables had been broken or fried, such that the inertia switch was not connected to the loom anymore. I simply twisted the broken leads together in the loom and the car fired up like nothing had ever happened! (I have now repaired this properly, such that the switch still does its job)

Moral of the story: be careful who you select to perform welding jobs on your car! Just prior to these troubles I had some serious welding/fabrication done in the floor pan area (both sides) - you can see where the heat has melted the inertia switch connector, so this was almost certainly what caused the damage.