Discovery 2 Crank no start, only 6c permanent voltage supply dtc

for me 30 - 87 are perpendicular(contact) and 85 - 86 parallel(coil) if on R4 INTERIOR FUSEBOX you dont have power across 85 - 86 while you crank it that's the reason to not have sparks as that relay feeds the ignition coils and this relay is completely managed by the ECU which if misses the crank signal(no rpm reading) it inhibits the sparks and injectors... a complex electrical trouboeshooing is needed done by somebody know how it works and can follow the diagram to see if the signal doesnt leave the ECU or it does but not reaching the relay and why the rpm is not shown, i can't help more from distance with this fault sorry... the ECU is quite suspect at this point but nanocom or similar is needed to rule it out

in a nutshell, you must get about 250 rpm reading with scanner while cranking otherwise it will never start but i can't tell how to achieve that without being there myself

Good morning and thank you very much for all the guidance Sieraferry, I opened the ecu to have a closer look and it has zero signs of water damage, dry joints etc, next thing I am going to look at is the connectors on the loom, are a couple that get water ingress. And what appears to be the main culprit the fuse box(cabin) with the internal relays. Also if i may ask, there are two orange coloured 4 pin connectors on each side of the head close to the firewall, do these go anywhere?

G'day... i can't help with those connectors but if you have a compatible scanner as we know you get no rpm reading watch all the other general inputs (battery voltage, coolant temp, air temp, manifold pressure, air flow, etc) which should be as for a cold start then watch the battery voltage while cranking...if it drops below 10V the ECU can't do it's job.... the engine can crank well even if the voltage drops to 6V while the ECU needs good power to work.

BTW if you don't get power across the ignition relay(R4) coil you shoud replace the fusebox with known good one to rule it out before chasing other issues

Just to repeat, I really appreciate all your time effort assisting me, and I am not getting power across R4 relay. :)

Quote:

---

Originally Posted by jassoyer

Just to repeat, I really appreciate all your time effort assisting me, and I am not getting power across R4 relay. :)

---

Then better rule out the fusebox before you go further

Hello, sorry for the long delay, took a while to get hold of an interior fusebox and then another... As my problem remains, are there any additional connectors maybe that I should look for to try resolve this, really dont want to send her to the breakers but its starting to really frustrate me now :(

I feel for you...after the fusebox swap do you get voltage on the ignition relay? or the main issue persist as still no spark?

Thank you for responding yet again :) Yes I now how power across relay R4 (Ignition). I can see on the scope I have AC signal when cranking on the crank sensor directly. No sure what to look at next... TAcho and diagnostic still show rpm and no fault codes.... Any more smart directions of attacking the problem are appreciated Sierra? So still the primary issue with no spark.

I'm running out of ideas as i'm not the best when it comes to petrol engine behaviour once the suspected electrics were ruled out...as long as it gets fuel alnd spark it should fire IMO but i know that the V8's can be hard to start if the MAF sensor is dead, can you see it's live input?... start it with spray maybe once started it'll keep running then you can watch all the live inputs or once it's running the ECU might identify some issue and throw a fault code

Problem is that it receives zero spark, have power going o the coils, but get zero rpm on the tacho. Which I believe is the cause of my issue.