Got a 2009 Diesel 1.6 causing me headache.

 

Started this summer with codes on clutch, brake and IC and a lot of random Canbus codes.

As the problems got worse this fall, with random warnings when pushing the brake pedal like “engine fault” etc, I decided to send the IC for re-solder. 
got it back with the words “no faults found”.

Problems escalated and the IC sometimes could flicker by itself with car turned off.

Now car is completely dead, worked 1 day outside, cold minus degrees, and left it in a warm garage 1 night and day after nothing works. Only central locking, interior light, outside lights and radio starts if u start them by hand like pushing radio on / off.

When I push the Start button there’s no reaction from anything, tried both keys. 
battery in car and in fobs are new.

If I open the door the screen in the Instrument cluster shows time / date etc, but nothing else.

No faults found with fuses. Checked ECU loom and contacts, clean and fine.

No signs of damage in BCM or RKE modules. 

Cant read all fault codes because ignition is off, there’s no other ways to start the ignition, where’s this car has no extra key holder hidden by the steering wheel, only a small slot for the metal key, no ways to turn anything on.

The only re-occurring fault code from the 4 modules I can connect to without ignition is RKE module and it shows “low system voltage” but the fuse in BCM is fine and the orange cable to RKE shows 12v+.
 

Fault codes in modules before this happened:

 

c1750, u1900, u2023, u193b, u0073, u0504 etc

 

Also forgot. Immobilizer light in IC blinks every 4-5seconds, does not matter if car is locked / unlocked.

 

So I’m guessing step 1 is IC change, but can’t read the old one because it seems dead, if I put in an other IC will I be able to put ignition on? 
Guess I can’t program the new IC if ignition won’t come on.

 

is there a difference between IS’s?
If I’ve got 8V4T10849GJ, can I buy say 8V4T10849LE and program it to the car?

Edit: Between IC’s I ment.

I’m guetting 120ohms between pin 6 & 14 on the obd connector, if I disconnect the big connector in fuse box under the hood and still guetting 120ohms. If I disconnect IC the ohms drop to 0.

Fun fact, while measuring ohm on pin 6 and 14 I removed the big contacts at the A pillars and ohm dropped to 60, now ignition works.

Still stuck with U1900 on IC and 1 code on ECU (PCM), brake switch correlation P0504.

This is beyond the scope of an enthusiastic amateur like yourself. You need a professional Auto Electrician with the access to full schematics and the appropriate test equipment. You have already covered most of what you can do.

Changing the Instrument Cluster will make the situation worse. The PATS system will not allow the vehicle to start if you change the IC.

The two main likely problems are a failed BCM and / or a faulty IC.

Do you have FORScan ?

10 hours ago, unofix said:

This is beyond the scope of an enthusiastic amateur like yourself. You need a professional Auto Electrician with the access to full schematics and the appropriate test equipment. You have already covered most of what you can do.

Changing the Instrument Cluster will make the situation worse. The PATS system will not allow the vehicle to start if you change the IC.

The two main likely problems are a failed BCM and / or a faulty IC.

Do you have FORScan ?

Don’t have Forscan yet but I will get it. Ive been using Autel MK906 so far for fault codes and live view.
I’ve got access to schematics so no problem.

As I don’t really have time to fault search long sittings, I had about 2hrs today and managed to get the car working.

I’m not sure the culprit here is the BCM, sometimes brake lights don’t light up, also get “Engine malfunction” warning.

Next step is to follow the schematics from ground - brake switch and further on, measuring the pin on IC to brake switch is ok, but next step is to follow that line all the way to the brake lights.

I know correlation fault is because PCM is getting mixed signal from the brake switch compared to the IC, so fault is either in IC or most likely harness.

Because the fault codes only activate after brake pedal has been touched.