Engine immobiliser fault - Citroen C5 2003 Hdi

Mycroft H

Hey there!

So I was changing the bulbs in the C5 yesterday and I disconnected the battery without thinking the keys were in the ignition. Totally forgetting there's a knack to disconnect the battery in the C5 without confusing the BSI (Body Control Unit)

So yea I've broken/confused the hell out the ECU and it's not recognising my keys (none of the three)

I've tried resetting the BSI using the recommended way on the citroen forums on the web but to no success.

I think it's definitely immobiliser related; it's cranking fine and I can hear the lift pump working when I turn the ignition.

So, what's next. Local Citroen fella with a lexia box says I'd have to buy new keys and pair them, you can't reprogram the old ones.

It's also stuck with the window down as it's gone into economy mode cos it's not been started. Thankfully it's not rained today

Any other tricks or do I've to get this towed to a dealer?

Mycroft H

The AA fella came and could do no more than I. It's not OBDII compliant, so neither of our fault readers would talk to it. It's going to a garage with a lexia box in the morning.

Ded_Zebra

166s can develop a similar problem. You can bring them back to life by unplugging the immobiliser "box" and plunging it back in again. The main dealers will tell you they will need new keys/reprogramming. Might be worth a try?

I assume you also tried disconnecting the battery again and waiting and trying again?

Mycroft H

Yea, I've been through the rigmarole of connecting the battery, turning the ignition, pushing buttons etc. Immobilizer box? The coil around the ignition.

Ded_Zebra

Mycroft H wrote: »

Yea, I've been through the rigmarole of connecting the battery, turning the ignition, pushing buttons etc. Immobilizer box? The coil around the ignition.

On the 166 there is a separate little computer for the immobiliser. It's up under the dashboard and it's a blue plastic box. If you unplug it and plug it in again it fixes the issue.

Obviously the C5 is going to be configured slightly differently! But if you can find the box that has the same function it may fix it too. Just a thought really. An optimistic long shot if you will

davycha

Are you sure you did not blow a fuse while disconnecting battery/ changing bulbs? ,
This happened me on a 406. It took me quite a while to figure out that I had inadvertently popped a fuse which was part of the immobiliser circuit . worth a check before reprogramming keys, etc.

shietpilot

Seems like a fairly crappy design if the immobiliser is losing memory from a battery disconnection

Mycroft H

They're fussy about how the battery is disconnected from what I can see. Bit like switching a computer off by pulling the plug insead of shutting it down

biko

Mycroft H wrote: »

I've tried resetting the BSI using the recommended way on the citroen forums on the web but to no success.

Like below?

Put the drivers window down and lift the bonnet (leave the key in the ignition)
Ensure all equipment (stereo etc) is switched off
Ensure all doors are closed and reach through the window to remove the key from the ignition
Wait 3 minutes
Disconnect the battery and then wait 15 seconds
Reconnect the battery and wait 10 seconds (Do not open any doors)
Switch on the ignition (but don't start the engine) and check that all tests pass
Hold the lock button on the key down for 10 seconds
Remove the key, open the drivers door, close it and check the central locking works (I had to hold the lock button down for another 10 seconds at this point)
Start the engine and complete the systems check

Mycroft H

biko wrote: »

Like below?

Yes, tried that and variations of that too.

Just off the phone with the Dealer. ECU had to be reprogrammed for the car along with the key code. Dealer said he'd seen the issue before and accodring to Citroen it can be caused by a power surge and requires the ECU to be reprogrammed by lexia.