I've a problem with a Ford Focus MK2 and looking for advice as I don't want to run into mad costs, here's a quick introduction on what happened:

  • Battery went flat - as radio and lights were turn on for too long without engine turned on.
  • Car was jump started - it gained electric power back again, however it didn't start.

  • On ignition the lights on dashboard light up and it says 'Engine systems fault' and there's no error codes on OBD reader. Immobilizer is also rapidly flashing in red, then it starts giving a PATS code.

Just as a note on ignition something in the engine makes noise - but it doesn't sound like any mechanical component.

Are there any next steps I can take to solve the problem myself?

Looking forward hearing from you.

Thank you! Adam

  • So it did start when you jump started it, but now it won't start again without a jump? Or just the lights came on when you tried to start it, but it has never started?
    – JPhi1618
    Commented Apr 25, 2016 at 19:14
  • It didn't start when we jump started it and the car won't start at all, it just says 'engine systems fault' on ignition and dashboard lights. Commented Apr 25, 2016 at 19:15
  • What is the PATS (Passive Anti Theft System) code that is displayed?
    – JPhi1618
    Commented Apr 25, 2016 at 19:25
  • Thanks @JPhi1618 - I'll have to read it out and update post - as don't know yet. Commented Apr 25, 2016 at 19:28
  • Do you have two keys for this car? Have you tried both keys? The Perimeter AntiTheft System checks the keys (via Radio Frequency Identification -RFID) with a small antenna located at the ignition switch. If it sees a good key, it allows the engine to start. Without that code it will never start ever. Do both keys fail? the two keys have different id's. The car learns the ID of the keys. Don't know why the jump start would clear out the code from the engine computer. Perhaps a weird voltage spike reset something? If you have one good key, there is a procedure to relearn the other key.
    – zipzit
    Commented Apr 25, 2016 at 21:45

1 Answer 1


I don't own a car with an immobilizer in it, but as I understand how they work, there is a code that must be entered, somewhere, to get the car to start if the battery was disconnected or gone flat. They even sell a device that holds up the radio and the immobilizer while the car is being worked on. It's basically a power source that plugs into the cigarette lighter and puts voltage into the system and allows just enough current to hold things up but not create a problem if shorted.

Your vehicle manual should have a section about the immobilizer and what to do if it is preventing your car from starting. I hope you have the code for the car, as otherwise a trip to the dealer may be required.

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