Hello everybody, I have a DTC in my DSG and need some info. I have 2021 Superb 3 combi 2.0tdi 150ps dsg. Some historical info

 

30.06.2024 --> P0C2B 00 DTC appeared

22.07.2024 --> Battery was completely empty after 5 days of rest. I jump started and drove the car of 1 hour and left parking

23.07.2024 --> Battery was so low, engine didn't crank. I jump started. Dealer did battery check (hot engine after 3 hours drive), battery health was ~74%. I replaced the battery, not to have any problem in winter.

18.11.2024 --> Car is serviced. Service did battery health check, they measured 12.4V. They didn't suspect but it is suspicious for me. I drove the car for 1 hour, left for parking, measured battery by myself 10min later, it was 12.7V

20.11.2024 --> After 36 hours rest, I measured the battery voltage (10degC), it was 12.07V!

 

So, I think something is depleeting the battery.

 

So far, I couldn't check the fuses one by one, but I am suspicious that TCM is not sleeping because of this fault.

 

I read that this pump is a support pump to the main pump (I couldn't locate main pump in the service manual) in case of Start-Stop function, to improve overall vehicle efficiency and main pump durability etc.

 

First question: If TCM is not sleeping because of this fault, how can I make it sleep? I have VCDS, I clear the DTCs but this one keeps appearing.

Second question: Let's say I live with this fault, use the car regularly to avoid dead battery. What could happen to the vehicle? Any damage to the transmission?

 

Thank you!

Edited 22 November, 20241 yr by idikmen

Well, you could always start by the simplest thing, which is simply your battery is about to die. The fact tht is 3 yr old is irrelevant, the quality of these components have dropped considerably. My own car has sometimes a longer than expected cranking after several days (I do not daily) and I take this as a symptom of age.

Have the battery checked properly from an auto electrician service, not Skoda, and evaluate.

You will have time to get into the more complicated things later ....

I am confident about 4 months old brand new battery (which has almost same production date), so, I rather focus on my pending questions. Though, thanks for reply.

I had a similar battery problem with my Superb 2. After 4 days without use, the battery was comletely drained. I put my battery on almost permanent trickle charge! The independent diagnosis was a faulty Body Control Module, with an estimate of £300 to repair. As I'd need to replace tyres too, I put the Old Girl in pex for the current Superb 3 L&K.

 

I can't say that your BCM is faulty, but it might be worth looking into.

 

Please report the final outcome back to the group, and good luck in finding a solution!

On 23/11/2024 at 14:06, idikmen said:

I am confident about 4 months old brand new battery (which has almost same production date), so, I rather focus on my pending questions. Though, thanks for reply.

Sorry, I neglected to read properly you had already gone for a new battery.

Then you need to go circuit by circuit to determine which stays 'awake' and drains battery.

You should get a good tester to measure mA, close/lock the car - remember to flick the switch of the bonnet, and measure ... after some minutes the car should go to 'sleep' and draw should be minimal, if not, something is up ...

If is something you do not feel confident to do, try to look for a "old time" auto electrician ... I have a fella that has saved me more than once, also on modern vehicles!

Good luck!

Some update:

 

I tried to measure the parasitic loss but failed, probably the cables that I have are  too thin. Then, I used a clamp current meter, it measured max 0.1A. However, it is not precise since the minimum measurement range is 40A and it is easily effected by earth’s magnetics. Yet, even 0.1A shouldn’t deplete the battery that fast.

So, I did some measurements with my friend over VCDS. What we have seen that alternator can provide up to 80A, but battery charge rate is around 5.2A when SoC is ~50%. Battery adaptation is correct and charge rate is not effected by engine rpm.

Normally, I use the car always with start/stop and I drive 12km one way to the company. Considering the values, it seems like I don’t give chance to the battery to be charged. Maybe I measured maximum battery voltage too quick last time? I might need to wait around 10 min before checking it.
New question: How can I check if the charge rate is normal or not?