Hi there, I've just changed my battery for a brand new one tonight and now my can won't start. Everything works (I put the code in for the radio and that works now) but when I go to start nothing happens, no click or anything. The odometer looks strange too, just has dashes, no numbers but it does when I'm not trying to start it. Any help or advise would be greatly received, especially as I need to get to work tomorrow! I'll try an upload the video of it too.

Hi!

Sounds to me like the new battery is either flat or a duffer or you may possibly have a bad connection on one or other of the terminal connections, or maybe the other end of the same cables.

Try re-connecting the battery first. Then If you have a volt meter try connecting it to the battery and see what the voltage is without turning the key. It should be no less than 12 volts without the engine running. When you try to start it the voltage shouldn't drop much with a good, new, battery. If it drops considerably then it is either flat or a duffer. Try charging it first before taking it back to the supplier. (This shouldn't normally be necessary with a new battery, they are usually fully charged when you buy them, but i would give it a go.)

Hope this helps!

Steve.

I've done all that and nothing, not even a click. There's nearly 13v on the battery. I did disconnect the wiring lume to the fuse box for ease of access, could it be a security thing?

Thanks for the ideas though!!!!

If the speedo show dashes instead of the mileage I think that means communication between the PCM and HEC has been lost, the result of this would be that the car would be immobilized because of the lack of communication between the two ECU's. I have been doing a lot of messing around of late with Ford IDS and reading a lot of things and this springs to mind for some reason, not quite sure why though. So I could be wrong.

So the loom I disconnected could have caused that? Is there a fix?

I've done all that and nothing, not even a click. There's nearly 13v on the battery. I did disconnect the wiring lume to the fuse box for ease of access, could it be a security thing?

Oh yes that has made me think, do you mean the large connector in the fuse box? If so I did that and think I had the exact same issue but I was messing around with it for other reasons, remove and reinsert it maybe even several times making sure the pins are not bent the connector is properly lined up and seated correctly. I spent ages trying to sort mine and after a couple of attempts I got it back in just right.

It was only reading your post saying you had disconnected that made me remember I had the same issue. Think it is the C90 connector in the fuse box.

Read this, this is what I was thinking of from when I did the same. Try cleaning the contact as well if you have some contact cleaner but WD40 won't really help as that only displaces water, needs to be contact cleaner really.

http://www.bba-reman.com/forums/PrintTopic105974.aspx

That the one, the large blue one cheers i'll give that a go!

I've never come across a problem like that on any car, of any manufacture. Most recently I replaced the in car fusebox on a 1.6 petrol C-max. Obviously disconnecting the battery before swapping it. The only thing that was lost afterwards was the radio code. 2 minutes later and that was restored. Everything else stayed the same. No security issues at all.

I'm not saying that is guaranteed to be the same on your model but you would think that Ford would stick with the same across models wouldn't you? Particularly in the same year.

If I have any other ideas I will post.

Good luck!

Steve

Definitely your problem too much of a coincidence to not be, but like I say it took me several attempts to get it back in correctly.

I've never come across a problem like that on any car, of any manufacture. Most recently I replaced the in car fusebox on a 1.6 petrol C-max. Obviously disconnecting the battery before swapping it. The only thing that was lost afterwards was the radio code. 2 minutes later and that was restored. Everything else stayed the same. No security issues at all.

I'm not saying that is guaranteed to be the same on your model but you would think that Ford would stick with the same across models wouldn't you? Particularly in the same year.

If I have any other ideas I will post.

Good luck!

Steve

I only know it because I did the same and spent 2 days panicking I had killed my car, after googling I found that website I linked to and reseating the C90 connector as suggested several times eventually sorted it. I had erased all my keys with IDS and reprogrammed them, I had erased the PCM and reprogrammed that too before I found that and that did indeed fix mine. So I'm about 99% sure it will solve his problem. Especially as he has said he removed that connector.

Problem is all the ECU's have to talk to each other via twisted pair line, if they don't then nothing will work properly. modern cars have some fancy stuff but when they go wrong they go wrong and all hell breaks loose.

My other car the ZTT uses a K line for all the ECU's to talk to each other, my sat nav drive got wet in the boot and all hell broke lose on my car on the motorway. back wiper going non stop, dials going crazy, interior lights coming on and off and bonnet warning coming on and all sorts, unplugged the sat nav drive and all went back to normal. Cars can be a real pain in the !Removed! these days.

Thanks for all your help guys. Disconnected and reconnected the C90 a few times and we're a goo again! Thanks!!! :-)

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All working now, but the battery light stays on until the engine is warm and stays above 2000 rev. Only done a short run this morning but as said before I changed the battery last night for a brand new one. Could this just be due to the faffing about and drained the battery a bit yesterday or could this be something more expensive? :-/

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Just changed my battery.All warning lights on car won't start ,warning engine service required,various other fault warnings.Unplug the large connector to the fuse box-I believe it's the C90 according to a previous post- plugged it back in,car started and all seems to be ok. Thanks to advice on this forum.

Thanks Simcor, Life saver. Just changed the battery on my 2016 Focus ST and then the car would not start. Engine service required (red spanner) and other hill start warnings in amber etc. Everything else worked, windows, heater everything. Battery symbol would not stay on when ignition was on and OBD reader said connection failure.  I had taken the C90 connector out of the fuse box to assist the new battery fitting. So I did take this C90 plug in and out a couple of times but nothing changed, the car still would not start. I would say that the C90 plug felt as though it was in properly, good fitment and secure so I was positive it could not be this as per the thread above and was about to take it to an auto electricians as I thought I must have knackered the ecu or something. Anyway in a last ditched attempt I spent over an hour fitting and refitting the C90 plug ( even though I would say that like above it felt a good fit, all of a sudden I got different error messages which spurred me on more to plug it in and out and re test trying to start the car.  Then no error messages. Left ignition on for 30 seconds. Switched off then on again and everything has now sprung back to life and she starts on the button every time.   I would not have believed it was the C90 plug unless this had happened to me as it had previously clicked into place and seamed okay. Thanks again

Thanks to this forum I avoided what would probably been a very expensive trip to Ford.  I changed my battery and had the exact same problem with the big blue C90 plug but didn’t know it until I found this forum. I was really starting to panic for a while their! 
 

THANKS EVERYONE!!

Hello all,

where is this C90 connector located in a Fiesta MK7 (2012-2017) please?

It is definitely not in the fuse box.

Thank you,

Hi there,

I had exactly the same problem with my Focus MK3 after battery replacement.
I switched off C90 connector to easily pull-out a battery.
After completing my job I was welcomed with 'Engine failure' message.
I was advised to clean the connector with some contact cleaner spray (WD-40 Specialist Contact Cleaner for example, but must be a contact cleaner spray).
I had cleaned it several times and finally I sprayed it a lot and then it worked after connecting back the C90.

You can also try to push it a little so that all pins could fit.
I hope it will help others as well.

Thank you, my ford didnt want to start at all, c90 plug helped!!!