Citroen C2 - dead electrics - No power to locks, interior light, ignition - everything dead

[napping]

OK next checks.
Is Fuse 8 in the under bonnect fusebox live (at both sides) all the time?
Fuse 13 in under bonnet fusebox is it ignition switched live at both sides?
28 way grey connector on under bonnet fusebox do pins 19 & 26 have a good earth?

Fuse 13 under bonnet fusebox is dead with the ignition on or off. Is that significant?
(Fuse 8 is live both sides. Pins 19 & 26 have a good earth.)

[ozvtr]

F8 fuses the supply of power to the starter motor solenoid. That question was from back in the days when we were looking at why the starter wasn't engaging. We know why now.
F13 fuses a supply going back to the BSI. That only proves that R6 in the BSM is not being energized. Again, why does the BSM supply power back to the BSI in that fashion? It could be benign or it could be important, just don't know (sorry).
Without further evidence I can only surmise the BSI is not talking to the other ECUs and they are just sitting there waiting for instructions.
The next logical step would be to see if any of the BSI BUSes are working. To my knowledge the busses should have a DC voltage of about 2.5V. Unfortunately that doesn't prove that there is any information traveling across it. I would disconnect the 40 pin black connector at the BSI and probe pins 27 and 25 (to ground) in the BSI connector. If my theory is correct that BSI bus will be dead.

[Dormouse]

Is it worth supplying a temporary power lead to F13 to see if the BSI comes to life?

[wheeler]

Is it worth supplying a temporary power lead to F13 to see if the BSI comes to life?

I was going to suggest this but if it wakes everything up it doesn’t really prove anything apart from the connection from F13 to the BSI is ok.
Have we checked the resistance of the CAN high lines? Should be 60 ohms.

[Dormouse]

Yes, but it narrows down the location of the issues.

[napping]

Is it worth supplying a temporary power lead to F13 to see if the BSI comes to life?

I was going to suggest this but if it wakes everything up it doesn’t really prove anything apart from the connection from F13 to the BSI is ok.
Have we checked the resistance of the CAN high lines? Should be 60 ohms.

I'm happy to try power to F13, so long as it's not likely to blow anything!
I haven't checked the resistance of the CAN high lines - where do I connect my multimeter to test this?

[Dormouse]

If you power up F13 with a fused lead you should be protected.

Anytime you want to power up any circuit to test it you should use a fused lead.

The fuse should be as low as practible, but never be higher than the rated fuse and, also, not too low to not allow "normal" anticipated start up current flow. If you are not sure what the start up current should be then use the rated fuse value.

Proper professionals use fully insulated, (changeable) fused probes and clamps and don't rely on wet string!

[admiral51]

Just a thought but does it has something to do with the immobiliser ?
Looking at what has been posted it seems that the correct handshake has not been sent and received after the original handshake from key and transponder if that is the correct term.
Key is accepted as okay, handshake good, but then the return handshake from immobiliser is not accepted so no start ?

Just thinking thats all

Colin

[Dormouse]

Possible, but would seem to answer only some of the issues. Diagnosis here is a nightmare. Back to plod on stage by stage I think. OZVTR seems to have the patience and understanding so lets see how it works out without jumping back and forward - step by step is what I would suggest.

[Dormouse]

Is it worth supplying a temporary power lead to F13 to see if the BSI comes to life?

I was going to suggest this but if it wakes everything up it doesn’t really prove anything apart from the connection from F13 to the BSI is ok.
Have we checked the resistance of the CAN high lines? Should be 60 ohms.

I'm happy to try power to F13, so long as it's not likely to blow anything!
I haven't checked the resistance of the CAN high lines - where do I connect my multimeter to test this?

Just had a thought. Only supply test power to F13 while the rest of the system is connected up too. Just powering any odd circuit could back feed an unintended circuit.

[Hell Razor5543]

Something a friend of mine would do when testing electronics was to have a lightbulb in the loop (but you had to work out the appropriate wattage first). If something started to draw too much current the bulb would light up, and also limit the amount of current that could flow.

[napping]

The fuse should be as low as practible, but never be higher than the rated fuse and, also, not too low to not allow "normal" anticipated start up current flow. If you are not sure what the start up current should be then use the rated fuse value.

Ok, I'll use a 10a fused wire and cross my fingers

[ozvtr]

Is it worth supplying a temporary power lead to F13 to see if the BSI comes to life?

I was going to suggest this but if it wakes everything up it doesn’t really prove anything apart from the connection from F13 to the BSI is ok.
Have we checked the resistance of the CAN high lines? Should be 60 ohms.

While I am not saying don't apply power to the BSI, I am with wheeler on this one. I am not sure it gets you any closer to a result. It would be nice to know if the BSM powers up the BSI...but what wakes up the BSM??!! I don't see any sensory inputs to the BSM except the CAN BUS from the BSI. So even if you do manage to wake up the BSI, (that way) where do you go from there? You are back to the CAN BUS.
Yes, if the BSI does power up, that throws a question mark over the BSM. BUT, again, you need to ascertain if the BSI is actually talking to the BSM. If the BSI is talking to the BSM...then the problem is with the BSM. If the BSI is not talking tot the BSM then it's the BSI. But either way you are back to see if the CAN BUS is working.
I don't have much experience with the 'BUS' structure so I don't know how you would test it with a minimum amount of equipment. But the first thing I would do is to test the impedance of the BUS (as wheeler says) and test if there is even any voltage on the BUS (on the BSI side).
This seems like an overly complicated way of controlling power around the car (if this is the case). But then I have found that some engineers do crazy sh!t.
However, having said all of that, I am interested to see what the results of your experiment are.

[ozvtr]

Oh! And if the BSI does not power up...well that doesn't prove anything!
My comments above are only made on the premise that the BSM is supposed to power up the BSI! But we don't know that.

I think you should check the CAN BUSes under all circumstances because, if the buses are not working you will get nothing out of the other ECUs, let alone to the BSM.

Yes, the resolution of your multi meter is not high enough to conclusively prove the BSI is dead. It could still be drawing a couple of milliamps and it not show on the meter, and it did react to the key in the ignition. Yes, power from the BSM could power up the BSI. So I concur the "BSM powers the BSI" is a valid theory BUT, again, It all hinges on the communication between the BSI and BSM being good.

For the "BSM powers up the BSI" theory to work the CAN BUS between the BSM and BSI must be alive all the time (I think) because the "wake up" inputs come into the BSI. If the "BSI powers the BSM" theory is correct then the CAN BUS can shut down when the car is "off" or the BSI is in sleep mode.

My little C3 (I have a Mk1 C2 also) is a pre-facelift (mk1) variant and the circuit diagram does not show a power line going from the BSM to the BSI. There is 1 power line going from the BSI to the BSM. The same as the F13 BSI, (not the F13 BSM) circuit in yours. Other wise I would try removing that power line and see, sorry. My guess is that the F13 BSM circuit is hard feedback to the BSI for some reason. Feedback that doesn't go through the CAN BUS? Don't know.

[Dormouse]

Napping would need precise details on how to test the Canbus along with precision meters. I personally have such equipment but it is a long walk to Napping and, as I have no experience on this model, I would want a precise wiring diagram to refer to. I reckon I would still be scratching my head for a long time.
If a temporary lead to F13 wakes the system you still have to track the fault and that is still not clear. However, it is something Napping can do with basic equipment in a short timescale and get back to the Forum with a yes or no.