[VeeJay]

I have 207 1.4 Hdi 2007 which I had installed a new clutch on and while putting back the ECU with the wiring harness connected, I hit the battery plus and I mistake this might be why the engine wont crank. Fault code said no communication with ecu So I did get a used ECU and tried to connect but still same fault code.

Tried jump starting the starter and it did crank but not start, tried this with both the old ECU and the new used one. I know the used one must be programmed to match the key or at least the Immobilizer must be removed somehow.

All fuses are ok. The ECU get 12v in.

When The old ECU gets connected there is a buzzing from the fuse box under the hood. This wont happen with the used one.

This is very frustrating. Have anyone experienced something similar?

 

[RedSector]

Not that this helps now, but in the future, always connect the earth (negative terminal) of the battery last to avoid any mistakes. When you're removing the two, earth (negative) off first, for the same reason.

 

[windy1603]

Can you get communications with new ECU even just locked message

Sent from my SM-G996B using Tapatalk

 

[VeeJay]

Can you get communications with new ECU even just locked message

Sent from my SM-G996B using Tapatalk

No communication at all

 

[VeeJay]

Not that this helps now, but in the future, always connect the earth (negative terminal) of the battery last to avoid any mistakes. When you're removing the two, earth (negative) off first, for the same reason.

I know, it was a stressful operation. Had to hurry

 

[jonathanh]

Sounds like the ECU is not powering up. You need to trace the power feeds to the ECU to check they all work. Likely to be some fault on power side. Possibly even a burnt out loom!

 

[VeeJay]

Sounds like the ECU is not powering up. You need to trace the power feeds to the ECU to check they all work. Likely to be some fault on power side. Possibly even a burnt out loom!

Me and a colleague did measure 12v into what we assumed was the plus to the ECU (the contact closest to windshield, big pin) I will measure continuity in all wires coming from the fuse box into the ECU tomorrow. Its just difficult without a wiring diagram for the ECU. Is there a signal wire from fuse box to ecu? Maybe there is power to it, but no signal coming back? I don't know

 

[jonathanh]

There can be multiple live feeds. You do need specific wiring diagram to check it out I am afraid. Someone here may be able to help with that

 

[Jolbe]

Well...after many days wandering in the dark...it would be good idea someone measured/explained whether exu casing is even connected to ground. If not...all this debate is in vain. Touching positive terminal with case connected to Nothing...has zero effect on Everything.

 

[VeeJay]

Well...after many days wandering in the dark...it would be good idea someone measured/explained whether exu casing is even connected to ground. If not...all this debate is in vain. Touching positive terminal with case connected to Nothing...has zero effect on Everything.

Yeah if someone would know, i'd be glad. But to me it seems like this is the grounding for the ECU. I have opened it up but didnt see any traces of damage at all. No burnt spots or corroded. Makes me think that it might have gone on through the wiring or even took out a relay in the fuse box, but I don't know how this is wired so its hard to tell. Today I will try to measure all the cables into the ecu

 

[RedSector]

Well...after many days wandering in the dark...it would be good idea someone measured/explained whether exu casing is even connected to ground. If not...all this debate is in vain. Touching positive terminal with case connected to Nothing...has zero effect on Everything.

Of course, it is earthed. No sure why you think it isn't or possibly isn't ?

 

[Jolbe]

?? You just measure connectivity between ecu case and ground.... If none...you didnt burn the ecu

 

[Jolbe]

Of course, it is earthed. No sure why you think it isn't or possibly isn't ?

Dont know. Why should the case be earhed?

 

[RedSector]

Well, does your ECU work after adding positive power to it ?

 

[VeeJay]

?? You just measure connectivity between ecu case and ground.... If none...you didnt burn the ecu

Thanks. I will try, I think the short circuit went somewhere else other than inside the ecu. Will check later today

 

[VeeJay]

Well, does your ECU work after adding positive power to it ?

Will try, just need to know which cable is for main power for it

 

[Jolbe]

Why? You have to connect all the original connectors to it.

 

[VeeJay]

Why? You have to connect all the original connectors to it.

Yeah, but what if these cables are not working or there is something before the ECU which sends power to it? Im measuring voltage today and based on what I can read there is voltage in everything, but when I connect the old ECU, there is a buzzing sound from the fuse box which quite if I disconnects either the first or second contact on the ecu. This sound isnt there with the used one I bought.

Still no communication with ECU, and I have got fault codes on brake fluid level and oil level sensors.

 

[VeeJay]

Update. When I connect the old ECU with the buzzing from the fuse box, I get additional fault code engine fuse box power latch relay. So to me it points towards relay in fuse box.

This fault does not show up with the used ECU that I got

 

[Jolbe]

What does it even mean you cant connect? Did you go to Repair in Diagbox?