I have a fiat stilo 1.4(2004) plate.

It had an intermittent issue with the "car security manager loose connection" and the car wouldn't start sometimes, But when shaking the fuse box/power distribution unit just behind the battery the car would start.

It then got progressively worse up to the point where as if the power distribution unit even gets nudged slightly (like when you set off) the car cuts out completely.

I did have the AA come out and take a look at it and the fault code they read was "power distribution unit fault", which leaves me in a bit of a predicament because you can't just buy a spare one as it is programmed to the ecu.

Which means I would have to buy a second hand ecu + power distribution unit off the same car, would there be anything else I would need that is uniquely programmed to the ecu apart from getting the key re-programmed ?

the power distribution unit in question (ignore the red circles, it's the best picture i could find of it)

power distribution unit

  • It sounds like a loose connection has gotten worse over time. Is it within your skills to remove the unit, check all the connections and replace it?
    – JPhi1618
    Feb 16 '16 at 16:58
  • I thought that at first as well, I removed the unit, Took every connector apart, cleaned with contact cleaner, rebuilt the unit, checked all of the connections again incase one was loose, checked all of the earths, and the exact same problem, car started up, tapped the distribution unit slightly and it cut out Feb 16 '16 at 17:07
  • 1
    Interesting. At least you've done some work to try and fix it... Hopefully someone knows more about it than I do. I didn't even know that unit had circuitry that could go bad - I figured it was just a big, dumb junction box.
    – JPhi1618
    Feb 16 '16 at 17:10
  • Same, always thought it was just a box for holding the relays and covering a few wires. Feb 16 '16 at 17:25
  • Could you put up pictures of the cover or what each relay does? And the back side of the box as well? Given that you can shake the box and get your car to start you should concentrate on the connections. Make sure that all pins are making contact in the connector. What about the relays? I'd assume one of those would be a relay for the security system or the ecu. Have you tried swapping them?
    – Ben
    Feb 16 '16 at 22:48

As requested by @ducatiKiller,

At first I though the issue was with a loose wire or faulty connection in the fuse relay box (turns out there's no cpu or fuse board of any sort in there) it's just metal plates stacked ontop of eachother.

After much poking and prodding(and contact cleaner), it turned out that the case that held the two sides of the fuse box together had become slightly disfigured(i have a habit of hitting speed bumps at 30+mph), after much electrical tape and super glue the box is now fully closed and secured to the car again.

overall it cost £300+ for several diagnostics and many cans of contact cleaner when just inspecting the box and closing it properly would of fixed the issue.

Might also be worth mentioning that when the relays where struggling to make contact it was causing the car to misfire and throw all sorts of unspecific fault codes so that might be something for anyone else to check if they have similar issues

  • I'm amazed the shop missed missed this, given the comments you originally gave and the code in the computer.
    – Ben
    Mar 21 '16 at 21:12
  • I don't get it, what was causing the fuse box to lose connection? Is the box grounded to the chassis, how did securing it in place fix it? Mar 22 '16 at 8:58
  • @IhavenoideawhatI'mdoing the box is basically two two halves that slow together, one half holds the fuses and relays in place, the other half consists of metal plates that bridge together to create some sort of circuit. when the two halves aren't pressed together fully it doesn't create a flush connection for the relays to pass the current to the metal plates, securing it in place stopped the box from opening slightly which was causing the issue in the first place Mar 22 '16 at 10:38
  • Interesting, so the box is a part of the circuit. Mar 22 '16 at 10:52
  • @IhavenoideawhatI'mdoing apparently so, the relays on the box are used by the headlights, tail-lights, car security, power steering and ignition. Mar 22 '16 at 13:07

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