I'm having an intermittent problem with my jag.

Symptoms:
Car won't start.
Car will crank.
Check engine light flashes.

May be related to:
Car quit at speed
Check engine light flashes

I thought I would get some relief by hooking up a code reader to it. The code reader pulled down a P0430 and P0420 and frame data indicating this happened while the vehicle was running at some point and everything looks normal (temp, speed, RPM, fuel). I suspect these DTCs are unrelated as they correspond to catalytic converter issues.

So I know the code reader works to some degree. It won't indicate what fault the computer is complaining about.

My first guess in the dark is maybe a faulty fuel pump.

I'll start picking the problem apart since the frequency of failure is increasing (and annoying).

When the check engine light is not flashing the car starts and runs normally so I suspect a failed sensor.

Any ideas?

Submitted by sodium@captain… on Wed, 09/17/2008 - 17:44

New Information

I've found a relay in the circuit that is malfunctioning. I'm not sure the relay is malfunctioning but this is definitely related. When the check engine light is strobing (it's not supposed to do that is it? separate matter really but it's supposed to be ON for certain error conditions or OFF but not strobing, right?) a relay in the trunk is firing on/off too.

The relay is located in a weird location too.

In the trunk (boot? boot.) above the battery is the ECU and above the ECU is the hydraulics for the convertable roof and a block of 5 or 6 relays. On the right is a metal panel and behind that panel are 4 relays. One is dangling from the wiring harness and the other 3 are mounted on the metal panel out of sight. The middle of the 3 relays is a 30 amp bosch relay that is the one involved.

I'm not sure what circuit this relay is part of and I'm pouring through my manuals trying to figure this out. If you know what this relay block does please let me know as I've little confidence I can easily locate this in the jaguar manuals.

Submitted by bonnettoboot@e… on Tue, 09/16/2008 - 18:51

If anyone knows of shops where they do free OBD scanning we should make a list accessable on the site as this is a very important part of todays fault finding. As for the "sudden" cut out, are you saying it happened when you were drivinng at speed? It sound awfully like a crank sensor problem but first make sure you have fuel supply to the injectors.