No dash lights and won't start help!

[vovocals]

I bought a Mazda3 2021 from an auction in the USA. I have an issue with the car.

The dash light doesn't come on just the security indicator light is blinking
the key can unlock the car and there are lights in other areas of the car like the radio the ac the roof. The car won't even crank. We bypassed the bcm just to see if the dash light will come on and it did with all the lights on the dash on
the ignition isn't showing on the dash.

We have done everything possible but left with no clue. We are suspecting the bcm but not sure also to note is that the bcm is hot. We have looked at the entire wiring of the car and can find no fault.

Please help!

 

[vallis]

You mentioned in the other post "shattered engine fuse", what do you mean by that, a burned fused? If so, which one? There is more than one engine fuse. Did you check other fuses?

If the scanner can't communicate, then there is a problem with the wiring, the modules or the fuses, to start with.

Was the BCM damaged from the accident? You can disconnect it and try to scan again. If it is bringing the network down, you should be able to communicate with other modules, and you would know it's the culprit.

Also, post pictures of the damaged areas.

 

[vovocals]

Attached is the vechicle however now fixed
Attached is the shattered fuse box replacement
attached is the bcm, the bcm was not damaged from the accident

basically all the lights in the car is on apart from the dash light only blinking the security indicator light. just to check if the dash is faulty the mechanice bypassed it from the bcm and all the light with the error code came on but as you know the car wouldn't start that way

 

[vovocals]

it's been a very long day
So apparently there is a bad wiring issue on the car after the impact
We were able to 1st trace it to a faulty bcm sending current back to the fuse back with a non @ current,
We fixed that an the dash came on. we were able to connect our scanner
but can't connect to the ECU
We will look more into the wiring again and hopefuly find all the fault
the bcm is very hot

 

[MzdCX_5]

Man, that BCM is corroded, looks like it was underwater or got rained on. It's a very common failure. It sits very low on the driver's foot well. You need to use MDARS, any other scanner won't do. Lucky for you, it is a US car. For a small fee, you can connect to the US server: Mazda Service perform a forced ignition ON and do some reprogramming.
PCM does engine management only.
BCM is the main computer module. It does everything else in this car. If it got water on, nothing will work. A replacement costs $2500 to 3000 dollars in the US. Good luck.

 

[vallis]

it's been a very long day
So apparently there is a bad wiring issue on the car after the impact
We were able to 1st trace it to a faulty bcm sending current back to the fuse back with a non @ current,
We fixed that an the dash came on. we were able to connect our scanner
but can't connect to the ECU
We will look more into the wiring again and hopefuly find all the fault
the bcm is very hot

Disconnect the BCM and rescan, can you connect to the ECU?

 

[vallis]

Man, that BCM is corroded, looks like it was underwater or got rained on. It's a very common failure. It sits very low on the driver's foot well. You need to use MDARS, any other scanner won't do. Lucky for you, it is a US car. For a small fee, you can connect to the US server: Mazda Service perform a forced ignition ON and do some reprogramming.
PCM does engine management only.
BCM is the main computer module. It does everything else in this car. If it got water on, nothing will work. A replacement costs $2500 to 3000 dollars in the US. Good luck.

Where is the picture that shows the corrosion? There are several modules that perform main functions. We can't just say that the BCM is the main computer.

And no, it's fairly cheap to replace and program. FORScan is a great option to use for programming. A $20-$30 adapter with FORScan can do the job even on a used BCM; many are listed on eBay for around $100.

OP needs to verify if it is actually the BCM that's faulty. It could be a short somewhere.

 

[MzdCX_5]

Mazda completely changed the electronics on M3 since 2019. All other cars in Mazda lineup follow the same design.
Lots of modules were eliminated from previous generation. FBCM, RBCM, RCM SSU are all in the new BCM. Included Immobilizer and theft deterrent.
From those pictures I could see plenty of corrosion on the module bracket, for sure got water intrusion.
People try in the past to replace it with a used Ebay BCM module and failed. They can't erase the donor's VIN number. They end up paying dealership big bucks.
Forscan doesn't support gen7 period. It just works as a basic DTC reader. This car needs MDARS for trouble shooting and programming.

 

[vovocals]

Hi thanks for your response. it's appreciated
We don't think the bcm is corroded most likely the location where the bcm is housed might have let to the corrosion of the aluminum however we have opened the bcm box and everything looks good inside
Secondly we noticed the @tting of the vehicle was bad as there were some loosed wires. we began atting all the wires that needed it. now we can scan the bcm, the ac works. the push start was acting up so we ran a direct wire from the push start to the battery and the car now clicks
We still don't have lights at the ECU end so we want to try and work on that area today to see what's wrong. Right now the AC and all other lights including the dash lights now work but the push start still acting up

one picture shows how scattered the fusebox came and the second shows us rearranging it and putting it all together