has anyone had something similar to this happen after replacing battery on ford focus (specifically 2017)?

i took my old battery out, also disconnecting the sensor attached to negative cable and the large block fuse with the blue bracket.

however, once i installed the new battery and re inserted everything back into place, my engine no longed even attempts to start. I'm getting hill start light, service engine now light and a tire malfunction light. I then trid to plug my obd in to see if i could diagnose the problem but it would not connect.

I have also tried the fog light, hazard light battery reset method and the battery light doesn't even come on.

Then attempted to jump start in-case low battery voltage was the limiter and still nothing

completely lost on what to check for now

any help would be much appreciated

Hi,

Sounds like one or more fuses blew from the surge when you reconnected the battery. It's not common but does happen occasionally.

If you've got a multimeter then first test the battery voltage to confirm that's good. Then test each fuse in order until you find a blown one.

On 1/22/2026 at 7:43 PM, TomsFocus said:

Hi,

Sounds like one or more fuses blew from the surge when you reconnected the battery. It's not common but does happen occasionally.

If you've got a multimeter then first test the battery voltage to confirm that's good. Then test each fuse in order until you find a blown one.

i tested every engine and passenger side fuse for continuity and they were all fine, i also took out the air box and checked the midi fuses and they all tested fine too

On 1/22/2026 at 7:43 PM, TomsFocus said:

Hi,

Sounds like one or more fuses blew from the surge when you reconnected the battery. It's not common but does happen occasionally.

If you've got a multimeter then first test the battery voltage to confirm that's good. Then test each fuse in order until you find a blown one.

could it be a problem with the immobiliser?

1 hour ago, ConlanM17 said:

could it be a problem with the immobiliser?

I don't think so. You should see a 'key not found' message if it was an immobiliser fault.

Has the battery been tested? Some are faulty from brand new.

I'm surprised it's not a fuse but at least we can rule those out now.

If the battery is definitely good then I think I'd disconnect both terminals and reseat them again. I would also leave it disconnected for 30 minutes, then leave it for 5 minutes once reconnected so that the modules can all reboot in order. Hopefully this is just a glitch now.

20 minutes ago, TomsFocus said:

I don't think so. You should see a 'key not found' message if it was an immobiliser fault.

Has the battery been tested? Some are faulty from brand new.

I'm surprised it's not a fuse but at least we can rule those out now.

If the battery is definitely good then I think I'd disconnect both terminals and reseat them again. I would also leave it disconnected for 30 minutes, then leave it for 5 minutes once reconnected so that the modules can all reboot in order. Hopefully this is just a glitch now.

i've not tested the battery, but i did try a jumpstart which resulted in the same no crank no start

i will try disconnecting and reseating though, thanks

no luck in this either, still not work

On 1/26/2026 at 5:57 PM, TomsFocus said:

I don't think so. You should see a 'key not found' message if it was an immobiliser fault.

Has the battery been tested? Some are faulty from brand new.

I'm surprised it's not a fuse but at least we can rule those out now.

If the battery is definitely good then I think I'd disconnect both terminals and reseat them again. I would also leave it disconnected for 30 minutes, then leave it for 5 minutes once reconnected so that the modules can all reboot in order. Hopefully this is just a glitch now.

no luck here either still not working

1 hour ago, ConlanM17 said:

no luck in this either, still not work

Ok. One final test is to connect a jump lead directly from the battery negative onto a thick part of the engine or gearbox. That rules out a poor earth connection.

If it still doesn't start after than then I think we've exhausted all options for remote diagnosis and would need to get an auto-electrician out.

On 1/29/2026 at 7:40 PM, TomsFocus said:

Ok. One final test is to connect a jump lead directly from the battery negative onto a thick part of the engine or gearbox. That rules out a poor earth connection.

If it still doesn't start after than then I think we've exhausted all options for remote diagnosis and would need to get an auto-electrician out.

One more thing that I tried is testing the starter relay and it clicks fine under test

then I connected a wire directly into the connection point and the engine cranks but still doesn’t turn over when trying to start at the same time

does that narrow it down?, more and more thinking it’s an immobiliser issue

13 hours ago, ConlanM17 said:

the engine cranks but still doesn’t turn over when trying to start at the same time

Sorry, I don't understand this. Crank and turn-over mean the same thing.

Immobiliser faults trigger dash lights and warning messages. I'm really not convinced it's that.