BCM fault?

[minnie2026]

I have trawled and trawled the internet with no definative answers.
I have had my seat leon 2008 mk2 for 7 years and have come across several electrical gremlins in that time.
The car was originally purchased with a battery drain - which was found to be the fuse for the 'telephone'
Since then we have had several issues with door lock modules giving up
Headlight faults even though the headlights work when switched on - but they do flicker on start up along with the reverse light and reg lights.
There has been an ignition fault on vcds for some time codes 00576/00884/00883/01744/00885 - dispite these codes the car runs fine for the majority.
Most recently we are having a slugish start issue that we cannot get to the bottom of - originally torsion was out which has now been corrected to 0.74° - if the exhaust cam is adjusted minutely the car will star very quickly but we loose ALL performance and finding the balance between starting and performance doesnt seem possible. Injectors have been replaced along with seals but no significant differance. Maybe in tank lift pump at fault also?!

The straw on the camels back has been the reverse light giving up but not identifying on the dash untill after a full day of trying to trace the wires and fault. We have lead this back to the BCM as the light board works and all wiring has a good level of continuity however we have 0.1v directly from the BCM.

Due to this accumulation of faults im now considering whether there could be a weakness within the BCM but whats the best way to know for sure?
Also if it is the BCM is it as straight forward as having someone mimic/code the second unit with my cars data?

Thank you for an help!

 

[R3k1355]

You've replaced the battery right?

That gives all sorts of weird electrical problems when it's on it's last legs.

 

[mty12345]

Faulty coolant temp sensor can cause starting issues. You can check on live data that the value is roughly the same as ambient temp when the engine is cold

 

[minnie2026]

You've replaced the battery right?

That gives all sorts of weird electrical problems when it's on it's last legs.

Battery is brand new made no difference

 

[minnie2026]

Faulty coolant temp sensor can cause starting issues. You can check on live data that the value is roughly the same as ambient temp when the engine is cold

Ill give that a try in the morning

 

[minnie2026]

Gone out this morning to check temp sensor reading as advised... coolant temp was 13° ambient was 16° bitch of a bitch to start to double checked DTC reading while at the car... miraculously ALL faults were clear except for the known problems being reverse light, front left side light and hvac. Nothing on the steering column which is a first for a number of years.

We are going to look at replacing the coolant tekp sensor and going from there will update with findings

 

[R3k1355]

Is worth going and reading a few different sensors as it's easy to spot faults when the car is off.

MAP sensor, intake air temp and DPF pressure sensors are easy to spot being at fault with the car off.

 

[minnie2026]

awesome il give them a check over.

Replaced the coolant temp sensor and started after a full night soak... made a big difference to starting but still not perfect took around 4 seconds as apposed to 10 seconds
But now idles very badly untill theres some sort of heat in the system.

 

[R3k1355]

Might be worth unplugging the battery and leaving it overnight, reset all adaptations and see how the car starts in it's factory setting?

 

[mty12345]

Have a look at this https://wiki.ross-tech.com/wiki/index.php/00885

Check out special notes at the bottom. I would try replacing the electrical portion of your ignition switch. Ross-tech are the company that make VCDS, so they know these systems better than anyone.

As for the Temp sensor, 3 degrees off is fine, it only has to be in the same ballpark. Where did the sensor come from? If it was amazon or ebay, i'd probably reinstall the original as could cause issues itself.

Edit: Also see here https://wiki.ross-tech.com/wiki/index.php/00576 Probably where your battery drain was coming from

You should just be able to replace the electrical portion on the rear of the barrel, you don't need to replace the barrel itself

 

[minnie2026]

The steering faults completely went which was odd but they have now come back so im considering the switch already.
As for the temp sensor its original and appears to work fine on a multimeter and reads close to ambient after cold soak.

Found what appears to be a small leak on the tandem pump so have a feeling we have a backdraw issue because of this not sure though as the start problem predates the tandem pump leak.
We are currently in the process of going over EVERYTHING mechanically before we get the ecu read to double check we havent had a map/ecu fart.