Berlingo No Crank.. giving me a kicking !

[scopehead]

Berlingo No Crank
Berlingo 3 1.6HDI
VIN VF7**************[VIN obfuscated, can be read by forum staff]
2016 Diesel

Hi all

I do this (diag/car electrics/electronics) for a living, but this one has me stumped, hoping someone (DIY or pro!) can think of something I haven't.

One morning, no crank. No recent work or installations.
Only useful code set is in the BSI - 0528 - Absence of command of the starter - ie the BSI expects to see a voltage drop when the starter cranks and it does not - this says to me that the BSI thinks everything is just fine.
No sign of immo issues. Tested both key and transponder ring. In addition in the ECU I can see it's status is unlocked and BSI says Emission of encrypted data = Yes and Engine ECU locked = No

Confirmed car will crank (but not start) with power on pin 2 of the 5 pin on the BSM going to the starter, also same with grounding the wire from ECU to BSM (start relay ground command (pin 16/grey) with a testlight - cranks but no start - even with key in crank position. So BSM is OK (did swap in/out a good one earlier in the diag).
Confirmed clean CAN comms (with a 'scope) coming from ECU and from BSI - jumpered CAN lines round the ABS just in case.

Looking at the wire that is grounded by the ECU (16/grey) to signal start to the BSM I can see with ign off it is ground, ign on it elevates to 9.5v, crank does nothing. Having checked all P+G I cloned and swapped an ECU in ... no change.

At the BSI I confirmed that 4+6 on the 10 pin white are pulled high with Ign and crank respectively, confirmed that pin 9/grey on the BSM is pulled high on crank.

When talking to BSI live data with a scan tool it boots me out when key is put in crank position, it did this on 2 scan tools and the Citroen software with a genuine interface. - Have seen this before though so not reading too much into it.

Have done a myriad of other checks but at the moment it seems that the BSI is not telling the ECU to start the car or the message is not getting there , what am I missing ? Would seem an odd mode of failure for a BSI.

[PaulC5]

Have you checked the crank shaft sensor ?

[scopehead]

Thanks for the idea but it's a no crank, so the crank sensor would not come into it.

[RichardW]

Interesting that it won't start if you crank it. Is the ECU on line and talking sense? What does the live data say when it is cranking?

[scopehead]

That's a good point, everything is online and all live data is nominal with KOEO, but I have to say I have not looked at live data when I artificially crank it as I was focused on the no crank and assumed if I fixed that then it would start.
Definitely worth a look as it might give a pointer. I do know I can read live data from the ECU whilst in crank position, only the BSI kicks me out.

[scopehead]

So following on from the above I grounded the wire from ECU to BSM (pin 16/grey) with a testlight and as mentioned this means it now cranks on the key but does not start. - Which proves out the whole of the other side of the start procedure.
I looked at a few bits of live ECU data, and most things are there, noted no MAF data and no start signal, but it does have rail pressure and crank signal.

No injector control of course else it would have started.
So it does not look like the ECU is losing anything and the BSI is expecting a start.
Interestingly it has a calculated injector flow but no injector firing, just about 3.5-5v on the injector wires.

I have already come to the conclusion that the ECU has (load tested) powers, grounds and communications, there appears to be no other external issues - so must be the ECU - but I swapped it out once already! - Used ECU with identical issue ? not very likely but not zero chance either.

Any thoughts welcome...