Citroen C5 Engine Immobilzer Fault

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bonnybrigg
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Citroen C5 Engine Immobilzer Fault

Post by bonnybrigg »

I recently had this code come up which caused the car to turn over when the key was turned in the ignition but not start up.

There appear to be many threads all over the web about this but very few with any fixes. Below is the short story of my fault and how I fixed it. I appreciate it may not have the same cause as others, but at least its the story of a fixed fault.

I had been driving my Citroen C5 2.2 HDI estate all day including short trips around Banff where I keep my boat. I was constantly putting the windows down using the remote for my dog in the car.

Eventually after I had parked it on the pier, I left it for about an hour and when I went to restart it, the engine turned but the LCD display on the dash came up with 'Engine Immobilizer fault' and it failed to fire.

I eventually had it towed to my mates garage. I had checked all the fuses in the glove box and under the bonnet but none were faulty. I could not find a shop which sold the correct battery for my key fob, that day either so couldn't verify if that was the fault until the next day. I had just re fitted a new Sony Stereo to the dash, I thought this may have caused the fault, it had because I had not ensured that one of the terminals which connect power to the unit was completely covered with the insulating rubber sheaths and must have shorted out on the casing causing a fuse to blow in the dashboard fuse box. Whilst I was taking the stereo out to check it, it must have cause the fuse to blow after the engine immobilizer fault had occurred,after I had checked the fuses, confusing the matter.

I also put a new car battery in the car as the old one was a smaller size than the recommended one and had been struggling when very cold last winter so I assumed it was on the way out.

The symptoms at this stage were the engine immobilisor fault showing on the dash, the rear windscreen wiper activating when the ignition was on, lights and other accessories inside the car not working including the windows. When we ran a diagnostic check , it could not gain access to the BSI ECU nor the engine ECU.

Eventually after removing the BSI module from the fuse box under the dash, to the side of the glove box, my mate noticed one of the fuses (which the stereo caused to blow) had gone. I replaced it, put the BSI and fuse box back together, ran a BSI reset (do a Google search for this and you will get the procedure easily), reset the fob (again a Google search will give you procedure), and the car started.

We eventually worked out that initially the key fob battery had gone flat with constant use causing the Engine Immobilizer fault (which may have been aggravated by a dodgy battery). Then after I checked all the fuses, I had removed the stereo which caused the fuse to blow in the fuse box. This also caused the engine immobilizer fault to show, so in effect both the blown fuse and the flat battery in the key fob appeared to have caused the fault, which confused matters.

The boot does not unlock now, however, we can now get access to the BSI module through my mates scanner and should be able to reset it to sort this problem out shortly.

I hope this is useful.
Last edited by bonnybrigg on 24 Sep 2014, 08:54, edited 1 time in total.
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Re: Citroen C5 Engine Immobilzer Fault

Post by wheeler »

bonnybrigg wrote: We eventually worked out that initially the key fob battery had gone flat with constant use causing the Engine Immobilizer fault.
The battery in the remote has nothing to do with the immobiliser, it's only for the remote central locking, if you remove the battery from the key the engine will still start. The plain spare key that comes with the car doesn't even have a battery.
bonnybrigg
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Re: Citroen C5 Engine Immobilzer Fault

Post by bonnybrigg »

Perhaps it helped the BSI reset. If you read the many other incomplete threads elsewhere, the fault causes the BSI to become upset and does not allow communication with it nor the engine ECU through the engine diagnostics. After I changed the fuse and carried out a BSI reset, the dash LCD still showed the Engine Immobilizer Fault. I then did the key fob reset by turning the ignition on and holding the unlock button for 15 seconds etc. which got rid of the immobilizer fault and allowed the engine to start- go figure!
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Re: Citroen C5 Engine Immobilzer Fault

Post by bonnybrigg »

I've now found that the rear boot will not open and the rear wiper will not operate correctly. Also the button on the dash next to teh radio, which should lock all the doors from inside, does not work either. Put it on my maters diagnostics and the BSI ECU seems to think everything is okay. I've checked all the wiring for the boot and it appears okay. Back onto the forum to see if I can find a fix!!
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Re: Citroen C5 Engine Immobilzer Fault

Post by Hell Razor5543 »

I now would definitely have the battery checked, and go through the BSi reset routine. The C5 (and other modern Citroens) are finicky where it comes to the electrical systems, and can throw up glitches. While it does not always work, doing the BSi reset can often clear down these glitches;

BSI Reset / Battery Disconnect / Reconnect Procedure

Think of it a bit like shutting down a PC. When you tell the PC to turn off it clears down all the various running routines, flushes out the temporary files, and other tasks. However, if you just pull the power it (obviously) does not shut down cleanly, temporary files get left behind, and it is possible files get corrupted.
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Re: Citroen C5 Engine Immobilzer Fault

Post by Stickyfinger »

I will put my $$$'s on the battery as well.
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Re: Citroen C5 Engine Immobilzer Fault

Post by CharlieFive »

Thanks for the procedure on this, my C5 was throwing the immobiliser fault on the side of the road.

This saved me a lot of hassle! 😁

P.S I've only ever used my back up key and not the fob.
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