V50 Electrics : immobiliser fault wont start

[waverdale]

Hi
I’ve got a Volvo v50 2.0d 2006 and it wont start it says immobiliser fault and there is no starter motor at ignition point 3. I think it could be the washer water in the CEM fault that they seem to get even though my VIN is outside the recall.
I have tried a new ignition switch which I presume is plug and play no coding required which made no difference.
I have checked all the fuses under the bonnet and in the CEM, rather stupidly I pulled 3 x 15 amp fuses out at once and one had blown so it was either number 43,45 or 48 which in the manual are 43 phone audio ,45 electrical socket and 48 washer. There is spilt drink residue in the cigarette lighter but the fact it could have been the washer fuse is leading me down the CEM fluid path.
The fault code I am getting is U0140 lost communication with body control module.
The remote fob opens the doors etc and when inserted in the ignition unlocks the steering and all lights up as it should but when you try to start there is no starter turning and it says immobiliser fault.
I took the CEM out and it looked ok when I checked the fuses so I put it back in and there is no difference so all plugs were seated correctly. Now I have it out again and all the pins look ok no signs of corrosion, ive removed the bottom cover (not fuse side) and all looks ok so next I think I will take a photo of the fuses and remove them all and see if there is anything obvious under the top cover.
If it was washer fluid being sucked through the wire would you expect to see a green corroded pin or could it be under the whitCEMcover on the board.
Only other thing was when I tested it the first time the battery was a bit low and was getting more faults on the dash and the engine management relay near the headlight was clicking however now its charged up I just have the immobiliser issue.with the new fuse in the windscreen washers work.
Does anyone know of any other bits I could check before it heads off to the dealers just they have quoted half a hour labour £50 and will probably just give me the code i already have
thanks

[waverdale]

update i have taken the plastic covers off the CEM and theres no sign of any water ingrerss and nothing out of place on either side of the boards
not sure where to try next
also forgot to mention on my code reader it shows no current faults but 1 pending fault U0140 and when i go to clear codes it says cant communicate with car .

[waverdale]

sorry i am now replying to my own questions i must learn how to use this forum.
does anyone know what the 2 relays do in the CEM i have checked all the fuses but dont know if these relays have anything to do with the immobiliser fault that i have.i havent checked the numbers on them but if there the same i could try swapping them with the ones in the fuse box near the battery ?
thanks

[windyridge]

Hi, did you get this problem sorted, I have got the same problem and would like to ask , what was the problem ?

[waverdale]

hi
i have been told by the dealers that if the key goes in and releases the stearing lock and the CEM looks ok then it has probably just lost the code for the immobiliser and will need the software reinstalled, total cost is £35 for the software and a third of a hour labour so should be under £100.but remember i had tried replacing the new stearing lock first.
will be taking it in the next few days and will report back the result
thanks

[waverdale]

hello to myself, and thanks to myself for all of my handy advice!
in other words lots of people read the post but nobody comments.
anyway got it sorted and in the hope it may help others heres what happened.
bought the car as a non runner it would not start and displayed imobiliser fault see manual.
i checked all fuses and fully charged the battery.
re seated the plugs under the glovebox
i then fitted a new ignition switch £145 but made no difference.
took out the CEM from under the glovebox and checked both sides of the circuit board with no signs of water damage or corrosion.
towed it to the dealers who were absolutly fantastic, they had said over the phone if the key goes in and releases the steering then it probably needs the software re programming.
sure enough a third of a hour labor later it was up and running total charge was £85 and i got a refund on the ignition switch
£500 for the V50 plus £85 to fix = bargain

[LizardOfBodom]

Makes me wonder what causes the CEM to "loose immobiliser code" in the first place. I heard some stories of dreaded "immobiliser fault see manual" but lots were due to water ingress, hence lack of my input on that topic, but if CEM was ok and presummably still original to the car - why lost code?...
(just wondering out loud in general)

[waverdale]

i would presume it was a power spike possibly from jump starting. i dont know the recent history as i just bought it as a non runner however the negative battery terminal wasnt tight i had to wedge a screw in the terminal.i suppose its similar to a usb memory stick that can lose its data if you unplug it .
the car is running fine now apart from its got a few lights on the dash which the tech thought could be the box under the drivers seat so i will strip it when i get more time

[Clan]

Originally Posted by waverdale

i would presume it was a power spike possibly from jump starting. i dont know the recent history as i just bought it as a non runner however the negative battery terminal wasnt tight i had to wedge a screw in the terminal.i suppose its similar to a usb memory stick that can lose its data if you unplug it .
the car is running fine now apart from its got a few lights on the dash which the tech thought could be the box under the drivers seat so i will strip it when i get more time

It is a known fault that if you leave the battery flat on the 2.0 D engine for a longer period the ECM ( not CEM ) looses it's memory and needs the software reloading ...

[waverdale]

i cant fault the volvo tech in newcastle he had done a few of these so as you say a common fault. they even sent a text message once it was fixed containing a video explaining what he had done and what the other faults could be. from what you say it sounds similar to a bios battery on a motherboard that loses the data if it goes flat, is it volatile memory that can be erased as opposed to non volatile memory that cant be erased. could there be a small battery somewhere in the system or a capacitor that wont retain its charge once the main car battery is disconnected for a longer period of time.if so this could well happen again.