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Stephen Rothwell
Stephen Rothwell,
Category: Jaguar
Satisfied Customers: 691
Experience:  Director at Steve Rothwell Limited
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I own a 2006 S Type. The battery went flat when it was up

Customer Question

I own a 2006 S Type. The battery went flat when it was laid up for about five months. Now when the battery is charged the engine fires up for about five or six seconds and then cuts out. My mechanic said it is probably the immobiliser which needs to be reprogrammed. Thanks Pat
JA: Have you tested the battery with a voltmeter? And can you see if it's leaking or not?
Customer: Battery is fully charged
JA: What is the model of your '06 Jaguar?
Customer: 2.7 Diesel Luxury
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: No. All I did was try the two keys to ensure that each of them were able to start the car. My mechanic started it and kept it going by doing something on his computer but as soon as he took his finger off it the engine cut out
JA: Anything else you want the Mechanic to know before I connect you?
Customer: No
Submitted: 7 months ago.
Category: Jaguar
Expert:  Nicola-mod replied 7 months ago.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.
Thank you!
Expert:  Stephen Rothwell replied 7 months ago.


Thank you for your question.

My name is ***** ***** I am a fully qualified vehicle technician with over thirty years in the trade. Hopefully I can help you.

The problem you have sounds as though it is related to a poor earth somewhere in the system. This may be from the battery or somewhere else on the vehicle.

The scenario you have where the engine will run with the diagnostic connector is one that is quite common and one I have come across before. This will not always leave a fault code in the system.

The reason that the engine will run when the diagnostic scanner is connected is because this then gives a route to earth for the required components.

As the vehicle has been laid up it may be corrosion on any of the ECU terminals or engine earth terminals.

The computer the mechanic used should indicate any other problems such as low fuel pressure or crank sensor and so we should be able to eliminate these.

If the problem is not an earth one there should be a fault code of some sort in the ECU memory, and your mechanic should be able to access this using his computer.

I hope this answers your question, but do please ask me for any further details.

If this does answer your question please click accept and rate me, this allows me to continue.

Even after clicking accept I can continue to answer questions on the problem for you.

Many Thanks


Customer: replied 6 months ago.
Hi Steve
I have since established that it is not an electrical fault with the immobiliser or ECU.
Have you any ideas from a mechanical point of niew ?
Customer: replied 6 months ago.
No thanks
Expert:  Stephen Rothwell replied 6 months ago.


The only reason it would run when the diagnostic tester was connected would be due to an electrical circuit being completed that is not otherwise connecting.

Your Jaguar has an in tank fuel pump which feeds the high pressure pump on the engine, I would test that next to see if it is "A" getting a feed and "B" actually pumping. Mechanically problems with a diesel can only be related to fuel supply and so if you are confident that no ECU connection or earth faults are present then the problem must be fuel related.

I hope this helps but do please feel free to ask me any further questions.