ECU Questions

[very452001]

Hi,

 

If there is a fault with the ECU then does the ECU have its own warning light on the dashboard and what that light looks like if it does come on due to ECU being faulty?

 

Where is the ECU relay for my car and if I do need one then where's the best place to get one? Where is the main feed to that ECU relay?

 

If the worst case scenario does come down to faulty ECU then where's the best place to get one cheap and how much am I Looking at and are they easy to install?

[Breezy_Pete]

What problem are you trying to fix? Why have you decided it is ECU related?

ECU doesn't have its own warning light. ECU relay is in position 1 of the 'e-box' under the bonnet. Main ECU power feed from that relay is via fuse 13, I think, for your engine.

ECUs very rarely fail; the problem nearly always turns out to be elsewhere.

[very452001]

4 hours ago, Wino said:

What problem are you trying to fix? Why have you decided it is ECU related?

ECU doesn't have its own warning light. ECU relay is in position 1 of the 'e-box' under the bonnet. Main ECU power feed from that relay is via fuse 13, I think, for your engine.

ECUs very rarely fail; the problem nearly always turns out to be elsewhere.

 

Ok how do I make sure and rule that it isnt the ECU is faulty or giving warning signs that it is dying out?

 

Where is this e-box, do you mean the main fusebox next to the battery?

 

Ok theres both a relay and fuse via fuse 13 needed for ecu and wheres the wire feed for fuse 13?

 

Yes its for this similar problem:

 

https://forums.seatcupra.net/index.php?threads/1-9tdi-wont-start-when-traction-control-light-is-on.387418/

 

Or could be a faulty battery however for me to consider this can anyone confirm that a faulty battery can cause a engine to cut out while driving?

 

 

 

 

[Breezy_Pete]

1 minute ago, very452001 said:

Where is this e-box, do you mean the main fusebox next to the battery?

Yes

2 minutes ago, very452001 said:

Ok theres both a relay and fuse via fuse 13 needed for ecu

The relay is fed by a huge strip-fuse on its input side, fuse 13 is on the output side of the relay (along with several other fuses for other things) and feeds 12V to the ECU when the relay is energised.

 

Has the car been scanned with VCDS? If so, what fault codes are showing?

 

That thread you linked is about a non-start situation, but you're asking about cutting out while driving?

[very452001]

1 hour ago, Wino said:

Yes

The relay is fed by a huge strip-fuse on its input side, fuse 13 is on the output side of the relay (along with several other fuses for other things) and feeds 12V to the ECU when the relay is energised.

 

Has the car been scanned with VCDS? If so, what fault codes are showing?

 

That thread you linked is about a non-start situation, but you're asking about cutting out while driving?

 

Hi yes it is intermittent both cut out and non-start. Now the intermittent non-start I use to have feels like a permanent non-start now where the car doesn't start at all now due to that traction control light being on the dashboard similarly to the problem in the link I posted above. Is there like a safety feature to my car where if the traction controls fails it wont allow the car wont start at all with this safety override? If so why can't cars still be driven without traction control?

 

How do I reset the traction control light on the dashboard as I tried holding the traction control button but doesn't go away. Is there a way to reset the traction control?

 

One another thing I notice is I have a OBD error scanning diagnostic tool where if there is no traction control light on it connects and scans finding no codes and if the traction control light remains on it fails to connect that is linking error. 

 

Is there like a diagram or pic showing which strip-fuse is it and where is fuse 13?

[Breezy_Pete]

56 minutes ago, very452001 said:

Is there like a safety feature to my car where if the traction controls fails it wont allow the car wont start

I doubt it.

 

56 minutes ago, very452001 said:

How do I reset the traction control light on the dashboard as I tried holding the traction control button but doesn't go away. Is there a way to reset the traction control?

Don't know.

 

58 minutes ago, very452001 said:

Is there like a diagram or pic showing which strip-fuse is it and where is fuse 13?

I can look this evening, don't have access to the info at the moment.  Usually, the fuses are numbered in the plastic of the fuseholder.  

 

[KenONeill]

1 hour ago, very452001 said:

How do I reset the traction control light on the dashboard

Which one? Is it the one in the switch which lights up when you select ASR off, or the ASR failed light in the instrument cluster?

 

In the first case, it should go out when you switch the ASR back on. In the second case, you diagnose and repair the fault.

[langers2k]

Traction control should have no influence over whether the engine runs or not. I expect the light is trying to tell you something else...

 

For example, it's not unusual for people to remove the fuse(s) to the ABS module and completely disable ABS/ESC/traction control for track use.

 

1 hour ago, very452001 said:

One another thing I notice is I have a OBD error scanning diagnostic tool where if there is no traction control light on it connects and scans finding no codes and if the traction control light remains on it fails to connect that is linking error. 

 

What are you using to scan for codes? If you're unable to connect to modules I'd expect intermittent communication errors on most modules.

[very452001]

2 hours ago, KenONeill said:

Which one? Is it the one in the switch which lights up when you select ASR off, or the ASR failed light in the instrument cluster?

 

In the first case, it should go out when you switch the ASR back on. In the second case, you diagnose and repair the fault.

 

Both the ASR switch button light and traction control light on dashboard are on not allowing me to start the car. 

[very452001]

2 hours ago, langers2k said:

Traction control should have no influence over whether the engine runs or not. I expect the light is trying to tell you something else...

 

For example, it's not unusual for people to remove the fuse(s) to the ABS module and completely disable ABS/ESC/traction control for track use.

 

 

What are you using to scan for codes? If you're unable to connect to modules I'd expect intermittent communication errors on most modules.

 

Im using a general OBD error fault code reader. Does intermittent communication errors on most modules at the same time indicate the ECU is faulty? 

 

Cant be coincidence all modules are affected at the same time unless main ECU computer is corrupt or something.

[langers2k]

If multiple modules are complaining about intermittent comms it can still be a number of things including but not limited to:

- ECU failure

- Wiring to the ECU failure

- CAN gateway failure

- Multiple wiring failures

- Loose/damaged/micro-fractured fuse

- Corrosion in the fusebox

- Dying battery

 

Given the generic OBD reader isn't showing any faults, I'd very much suggest you use something VAG specific or at least have someone with genuine VCDS do an autoscan, clear the faults and autoscan again.

 

Couple of threads that might help you find a VCDS owner:

- https://www.briskoda.net/forums/topic/224376-vcds-owners-map/

- https://www.briskoda.net/forums/topic/262215-list-of-vcds-owners-previously-known-as-vag-com-vcp-owners/

 

[very452001]

1 hour ago, langers2k said:

If multiple modules are complaining about intermittent comms it can still be a number of things including but not limited to:

- ECU failure

- Wiring to the ECU failure

- CAN gateway failure

- Multiple wiring failures

- Loose/damaged/micro-fractured fuse

- Corrosion in the fusebox

- Dying battery

 

Given the generic OBD reader isn't showing any faults, I'd very much suggest you use something VAG specific or at least have someone with genuine VCDS do an autoscan, clear the faults and autoscan again.

 

Couple of threads that might help you find a VCDS owner:

- https://www.briskoda.net/forums/topic/224376-vcds-owners-map/

- https://www.briskoda.net/forums/topic/262215-list-of-vcds-owners-previously-known-as-vag-com-vcp-owners/

 

 

Im not sure whether it is multiple modules are complaining at the same time. All i know is my OBD error scanner tool is not linking to my car saying on its screen linking error. Does this mean multiple modules are complaining at the same time? If so how is it by coincidence these multiple modules all turn faulty at the same time unless its the faulty computer that controls them that is the main ECU is causing this right?

 

Im new to CAN Gateway what is that?

 

Is it possible to borrow a VCDS from someone or invite someone down with VCDS to do the scan as I cant start the car.

[nige8021]

Look on the links that @langers2k gave you and see if there is someone near you, then send them a PM to see if they will come and read the codes for you, as said a generic OBD reader is not the best tool to be using 

[langers2k]

In your car there are multiple control modules that communicate using CAN-bus.

 

However, there are actually multiple CAN-bus networks for different functionally and run at different speeds, for example:

- Drive CAN has things like the engine and ABS brakes

- Comfort CAN has things like the door controllers and HVAC system

- Infotainment CAN has the radio and bluetooth

- The instrument cluster get it's own network

 

Obviously some data needs to get from one CAN-bus network to another, for instance:

- vehicle speed from the ABS module to the instrument cluster

- cabin temperature from the HVAC system to the radio

 

To allow this, each CAN-bus network is also connected to the CAN gateway. It's job is to allow some data between the networks 

 

The OBD port connects directly to the CAN gateway. If it is faulty or has power issues, it'll stop you connecting any diagnostic equipment. It'll probably also create plenty of other issues, for instance the engine communicating with the instrument cluster to check the key matches the immobiliser. I'd be surprised if this was actually the problem as they tend to be quite reliable afaik.

 

As I say, the first step is to attempt an autoscan with VCDS, depending on the results that'll hopefully give the next step. A generic OBD reader really isn't going to cut it as VAG specific tools can access much more information and error codes from other modules.

 

You'll need to contact member closer to you to see if any are willing to take a look...

[KenONeill]

17 hours ago, very452001 said:

 

Both the ASR switch button light and traction control light on dashboard are on not allowing me to start the car. 

I don't understand why you believe that the ABS module (which controls ESR) is the base fault rather than a symptom of the actual fault. I'm pretty sure that @Wino and @langers2k think the ABS module fault is a symptom too.

[very452001]

15 hours ago, langers2k said:

In your car there are multiple control modules that communicate using CAN-bus.

 

However, there are actually multiple CAN-bus networks for different functionally and run at different speeds, for example:

- Drive CAN has things like the engine and ABS brakes

- Comfort CAN has things like the door controllers and HVAC system

- Infotainment CAN has the radio and bluetooth

- The instrument cluster get it's own network

 

Obviously some data needs to get from one CAN-bus network to another, for instance:

- vehicle speed from the ABS module to the instrument cluster

- cabin temperature from the HVAC system to the radio

 

To allow this, each CAN-bus network is also connected to the CAN gateway. It's job is to allow some data between the networks 

 

The OBD port connects directly to the CAN gateway. If it is faulty or has power issues, it'll stop you connecting any diagnostic equipment. It'll probably also create plenty of other issues, for instance the engine communicating with the instrument cluster to check the key matches the immobiliser. I'd be surprised if this was actually the problem as they tend to be quite reliable afaik.

 

As I say, the first step is to attempt an autoscan with VCDS, depending on the results that'll hopefully give the next step. A generic OBD reader really isn't going to cut it as VAG specific tools can access much more information and error codes from other modules.

 

You'll need to contact member closer to you to see if any are willing to take a look...

 

Ok I can connect my OBD error scanner tool when the traction control light is off the dashboard and I cant connect vice versa. From this can we rule out the CAN gateway fault possibility?

 

Like i just said above if I cant connect my generic OBD tool when the traction control light is on the dashboard then will it treat the VCDS the same where it cant connect too? 

[very452001]

2 hours ago, KenONeill said:

I don't understand why you believe that the ABS module (which controls ESR) is the base fault rather than a symptom of the actual fault. I'm pretty sure that @Wino and @langers2k think the ABS module fault is a symptom too.

 

So the ABS module wont allow me to drive the car with the ABS off if we assume the ABS module is faulty?

[nige8021]

Stop speculating as to what the faulty unit might be, get it scanned with proper VAG based diagnostic, then start the fault finding based on what that indicates 

[KenONeill]

12 minutes ago, very452001 said:

 

So the ABS module wont allow me to drive the car with the ABS off if we assume the ABS module is faulty?

Contrarywise; the fault is elsewhere simply because you can drive a car with the ABS faulty.

[langers2k]

19 minutes ago, very452001 said:

Ok I can connect my OBD error scanner tool when the traction control light is off the dashboard and I cant connect vice versa. From this can we rule out the CAN gateway fault possibility?

 

Like i just said above if I cant connect my generic OBD tool when the traction control light is on the dashboard then will it treat the VCDS the same where it cant connect too? 

 

Regardless of whether the ABS module is working, you should be able to connect to the diagnostic port and access other modules - at least if you're using VCDS.

 

Given you only seem to have a generic OBD2 reader, I'd suggest you contact a VAG specialist with the appropriate tools as we aren't getting anywhere...

[very452001]

1 hour ago, KenONeill said:

Contrarywise; the fault is elsewhere simply because you can drive a car with the ABS faulty.

 

Ok what do you think the next most possible fault is in meantime while I try to sort out a VCDS?

[very452001]

Ok latest update is I replaced the Battery and the ECU relay with a brand new ones however still the same problem 😭

[nige8021]

How many times do you need telling, get the fault codes read with VCDS and then post the results and you might to the bottom of the problem 

[very452001]

Ok AA breakdown guy came out and found no stored codes however there's 1 problem showing on his tablet screen and that is there's a communication problem with the ECU. He checked all fuses and relays and checked visually for wiring issues for wires viewable at 1st glance in the engine bay but couldn't find any. 

 

So he said its most likely ECU needs replacing and second most likely is issue with the wiring to the ECU however he said finding a fault like a kink in wire for example in the whole wiring harness in the car will require whole engine parts stripping out to trace and investigate the paths of all these wires which sounds more complicated that just swapping out the ECU.

 

So to investigate this wiring diagram requires a whole lot of parts needed to be stripped out to fully investigate and trace path each wire which sounds like a lot of man hours that equals a lot of £££?

 

I ask because my car when it was working was worth like around a grand I say so the $64000 dollar final question is that is it worth fixing?

 

Otherwise is it a good idea to send off a ECU off for repair or get a replacement used ECU? How much are new ones?

 

When sending off ECU off for repair does it still require reprogramming?

 

When putting a replacement used ECU in then what requires reprogramming and any hardware parts needs replacing to reflect this?

 

Are new ECU's from dealership or from a new stockist compatible with my car straight away and won't require reprogramming because part numbers match with old ecu and new ecu? 

[KenONeill]

8 minutes ago, very452001 said:

AA breakdown guy came out and found no stored codes however there's 1 problem showing on his tablet screen and that is there's a communication problem with the ECU.

Yeah, right! ;-)