S40 T5 won't start - Ignition switch?

[Clan]

Originally Posted by LizardOfBodom

Ok, so to summarise it up , let me know if thats correct:
SCU can go bad both ways:
- mechanically, where for example contats degrade and no longer recognise key position
- electronically, where components goes haywire and for example antennae no longer sends/receive signal or such signal is no longer passed from SCU to CEM.

In the 1st scenario, like FunkyMelon, you can hardwire the car as everything works OK bar the actual "START" position
In the 2nd scenario, you would not be able to even disengage SCL nor start the car as CEM would still be in "immobilised" mode.

Dose that seem right?

Yes that is correct , however I have never heard of the immobiliser receiver failing in the last 14 years since the car was launched .

[FunkyMelon]

There is a 3rd scenario which I have read about online a few times where apart of the CEM (or maybe it's the SCL) needs reprogramming as it's forgotten the code.

So all the other modules get the code OK and are in sync but because one has forgotten it/can't receive it, car won't start.

Car is useless and won't start/needs to be towed but the software is about £35 and you're on your way again....

[LizardOfBodom]

Originally Posted by Clan

Yes that is correct , however I have never heard of the immobiliser receiver failing in the last 14 years since the car was launched .

I have read few threads on US forum where people got "key error" already on POS1 with SCL not even disengaging, radio/fan not turning on etc. SCU was a fault aswell, but in those cases I think it was more down to antennae signal? I dont remember if they tried to hardwire it to start or not but something tells me it wouldnt.

[LizardOfBodom]

Originally Posted by FunkyMelon

There is a 3rd scenario which I have read about online a few times where apart of the CEM (or maybe it's the SCL) needs reprogramming as it's forgotten the code.

So all the other modules get the code OK and are in sync but because one has forgotten it/can't receive it, car won't start.

Car is useless and won't start/needs to be towed but the software is about £35 and you're on your way again....

But in that case it wouldnt start by hardwiring, would it?
I think in your case car is already "pass" the RFID inspection so there should be no more checkups prior to start?
If SCU is just a relay, it should work like this:
RFID code 123 in key is recieved by SCU and passed over to CEM. CEM compares 123 to 123 and decides "ok, thats the right key, I will disengage impobiliser and allow car to start when I recieve POS3 signal". In that case you can hardwire car by starter itself bypassing the SCU.
If CEM "forgets" the code, it will compare 123 to 000 and decide "nope, wrong code, immobiliser stays on" and in that case you shouldnt be able to start the car by hardwiring starter relay as its basically like trying to steal it without key.

Dunno, it all seem too complicated for its own good, but thats how I understand it :}

[Clan]

Originally Posted by FunkyMelon

There is a 3rd scenario which I have read about online a few times where apart of the CEM (or maybe it's the SCL) needs reprogramming as it's forgotten the code.

So all the other modules get the code OK and are in sync but because one has forgotten it/can't receive it, car won't start.

Car is useless and won't start/needs to be towed but the software is about £35 and you're on your way again....

that is only applicable to the 2.0 Diesel ecu ,, and only if you have left it with a flat battery for a number of days …

[FunkyMelon]

Originally Posted by LizardOfBodom

But in that case it wouldnt start by hardwiring, would it?
I think in your case car is already "pass" the RFID inspection so there should be no more checkups prior to start?
If SCU is just a relay, it should work like this:
RFID code 123 in key is recieved by SCU and passed over to CEM. CEM compares 123 to 123 and decides "ok, thats the right key, I will disengage impobiliser and allow car to start when I recieve POS3 signal". In that case you can hardwire car by starter itself bypassing the SCU.
If CEM "forgets" the code, it will compare 123 to 000 and decide "nope, wrong code, immobiliser stays on" and in that case you shouldnt be able to start the car by hardwiring starter relay as its basically like trying to steal it without key.

Dunno, it all seem too complicated for its own good, but thats how I understand it :}

Yeah I put that in the last line of my previous comment, it wouldn't work.

Basically, all modules in the car that are programmed with codes need to exchange and confirm they're happy with the code. If one isn't happy/doesn't talk back, it won't start.

The case I mentioned in my previous post leaves you stranded, the SCL doesn't have a code as it's lost it, cars dead as a dodo till that module is reprogrammed again.

Fortunately in my case, all the modules were happy with the code, it's just the signal for the starter coming from the SCU to the CEM was missing, hence why shorting the pins got it going, just mimicked the signal it would have got if Pos III was working

It's all far too complicated, great for dealers though - ££££££!

[wobblyprop]

Similar situation, 2009 V50 Automatic, had to get AA out twice in last 3 weeks, Starter does not crank via Key, been in garage, no fault found, AA just clip a lead onto battery then separate the starter connector cable block (feed from ignition not the main power feed) touch wire onto male pin in block and engine starts (with key in II Position and gearbox in Park) another sympton when this fault occurs is the Gear Indicator Light stays on when key removed, been in garage for 2nd time cant find the fault, now made myself a 3ft lead with battery clip on one end and just separate the lead to starter and hot wire it, takes a few minutes

[Vegastvt23]

Hi guys

My car has got some intermittent starting issues. Sometimes it starts well, sometimes it starts with a very low idle like it wants to cut off. Sometimes it cranks ,doesn’t start but if I press gas pedal it starts. I have these error codes
DIM-DF13 -CAN bus H signal too high intermittent fault
CEM-6C43-start control module SCU faulty signal(intermittent fault)
DE01-Communication with BCM control module signal missing.(intermittent fault)

Anyone experienced similar problems or have an idea what could be the problem

[Clan]

Originally Posted by Vegastvt23

Hi guys

My car has got some intermittent starting issues. Sometimes it starts well, sometimes it starts with a very low idle like it wants to cut off. Sometimes it cranks ,doesn’t start but if I press gas pedal it starts. I have these error codes
DIM-DF13 -CAN bus H signal too high intermittent fault
CEM-6C43-start control module SCU faulty signal(intermittent fault)
DE01-Communication with BCM control module signal missing.(intermittent fault)

Anyone experienced similar problems or have an idea what could be the problem

you need to renew the 3 pairs of network female wire terminals in the CEM plugs .. volvo do repair terminals with 6 inches of wire attached to make it easier .
or at least take the plugs in and out to clean the weak contacts ...

[FunkyMelon]

Originally Posted by Vegastvt23

Hi guys

My car has got some intermittent starting issues. Sometimes it starts well, sometimes it starts with a very low idle like it wants to cut off. Sometimes it cranks ,doesn’t start but if I press gas pedal it starts. I have these error codes
DIM-DF13 -CAN bus H signal too high intermittent fault
CEM-6C43-start control module SCU faulty signal(intermittent fault)
DE01-Communication with BCM control module signal missing.(intermittent fault)

Anyone experienced similar problems or have an idea what could be the problem

Unlikely you'll need new connectors...

Disconnect the battery, remove the CEM and clean all of the pins on the CEM and the connectors with contact cleaner and an old toothbrush.

Plug it all back in and you should be good to go.