Meant base of actual engine bay fuse box as in picture above. Think there are connectors underneath to ecu etc. Not unknown for a pin to be coroded or socket opened up enough to make bad connection especially if moisture is present.

Alasdair

Also you can check and R8 which is related to Engine electronic components

Tested the code after letting the car sit for 6 hours (cold engine):

• Cold Engine (Ignition ON, Engine OFF): The code was static and refused to clear. I tried clearing it 4 times in a row, but it reappeared instantly on every rescan without even starting the engine.

• Warm Engine: After driving to lunch and back, I cleared the code on ignition—it wiped cleanly and stayed gone.

Will check the rest of the suggestions when I come home.

And retray to clear fault when the engine is cold.

9 hours ago, digibum said:

DNFE / 2.0 TSI EA888 Gen 4 / 280 hp

Unfortunately I don't have recent enough circuit diagrams for Superb to cover this engine code.

@Breezy_Pete thank you for your effort!

This morning, I ran a scan on a cold engine and got the usual cold-start behavior, and refused to clear:

1. Immediate rescan: I cleared the code (P25AB00) on cold ignition. OBDeleven automatically rescanned the ECU a second later and caught the code again immediately. Checking the Freeze Frame data, I noticed a new timestamp and slightly changed parameters. I retried clearing it twice, and after each clear, a new timestamp and slightly changed parameters appeared.

2. The 60-second delay: After failing twice, I turned the ignition OFF, waited a full 60 seconds, and turned the ignition back ON. Upon scanning, the frequency counter had increased to 2. I cleared the code, and this time it stayed gone!

I then drove to work with no faults at all, and the Start-Stop system worked perfectly the entire way. A fresh scan upon arrival at work showed zero faults.

I also checked the fuse box in the engine bay — I pulled out and reseated all fuses and relays to ensure good contact. All pins and terminals look completely spotless with zero visible signs of corrosion or oxidation.

Edited 21 August21 Aug by digibum

Hope it stays gone. If it returns I think there should be a multipin cable from ecu in the engine bay fuse box. Not sure exactly where. On my octavia it seems to connect through base of box. Check it for loose pins/corosion. Hopefully it was a fuse/relay that needed reseated.

Alasdair

@digibum Any progress?

Still waiting... The service center has been waiting for two weeks now for a reply from the importer (tech support) to finally figure out what the next step will be. Honestly, I'm at my wits' end with them and I'm this close to calling them up and giving them a piece of my mind about why everything moves at a snail's pace.

1. The piston cooling oil control valve (N522) — replaced twice.

2. The engine wiring harness.

3. The main engine ECU.

4. A brand-new Varta battery (installed by the dealership after they noticed a big voltage drop when starting cold).

5. Checked all fuses and relays in the engine bay — everything looks completely clean with zero corrosion.

The dealership has officially admitted that they have completely run out of ideas on what to check next. They have submitted additional inquiries to the technical support team, but the support process is painfully slow, highly unresponsive, or simply leaving questions completely unanswered.

Current status: Despite replacing all these major parts and running all these tests, the issue is still not fixed.

Is it something to do with oil being too higher viscosity?

Piston cooling sounds like oil jets, so maybe try a thinner oil (specifically the cold viscosity) see if that helps the cold starting error problem

4 hours ago, BlueWagon said:

Is it something to do with oil being too higher viscosity?

Piston cooling sounds like oil jets, so maybe try a thinner oil (specifically the cold viscosity) see if that helps the cold starting error problem

Thanks for the suggestion! However, it can't be related to the oil viscosity itself because the fault code P25AB00 triggers instantly on ignition ON alone (engine OFF) during a cold boot, before the engine even cranks or any oil pressure is built.

Appreciate the idea, though!

Honestly, I’m just completely baffled by this whole situation.

How is it even possible that on a 2022 modern car, with all the advanced diagnostics, live parameters, detailed Freeze Frame data, and full ECU logs available, nobody—including the main dealer—can pinpoint the actual root cause of this error?

We have clear, repeatable patterns (ignition ON, cold boot vs. warm engine, instant re-trigger with live Freeze Frames), yet the troubleshooting relies solely on throwing parts at the car and blindly waiting for factory support. It's frustrating to see that with all this technology and data at our fingertips, an electrical cold-start glitch can still completely stump the entire service network. ☠️

Edited 5 minutes ago5 min by digibum