Papez

The only relay I can think of is R7 (X-contact), which powers wipers, headlights and other power hungry devices. It's also connected to the BE connector mentioned earlier. But it's driven by the ignition switch, so it can be either the switch or the relay.

Is the foam under the dasboard above the glovebox dry? Windshield leak is quite common issue on Felicias and water ends up in the fusebox, causing various electrical issues.

I can confirm now that leaking wastegate moves boost response up in the RPM range. I had some 4mm of total play in the actuator itself and the connection to wastegate lever and turbo didn't boost properly until 3000RPM. After actuator replacement, everything improved, though I didn't check the exact figures with the diagnostics.

So hopefully the issue have been fixed! The culprit was the wastegate actuator after all. Upon inspection I noticed quite significant play on the actuator rod. This was present even when the ECU tried to close the wastegate. So I ordered new part to try and replace it. MP4_20260914_080003VLOG.mp4 Getting the old part out was fight, too. I couldn't get the actuator off the wastegate lever. And this is why: I tried to move the lever before and there was no sign of play. So it's likely that the connection was sticking, but not enough to throw the P334B error. The bushing in the actuator, where the rod passes, was significantly worn, too, and the entire mechanism didn't move as freely as the new part. Overall, there was 3-4mm of play in the system (for reference, the entire range of the actuator is 10mm - reduced by 2mm insert which was fit during recall), so it's no wonder that the turbo couldn't reach boost in lower RPM. After the replacement, I did 15x ignition on/off procedure, which supposedly resets the endpoints. Drove around 200km afterwards with no issue. The car is much more lively now, although I didn't check with diagnostics, it's apparent that turbo reaches full pressure at ~2000RPM, but the throttle response improved all the way to idle. Fuel consumption at 6th gear/2000RPM and full throttle went from 9-10l/100km to 15+, so there's definitely more air going into the engine and hills, where it struggled before, are no issue now.

Here's the diagram. The R5/J17 relay on the top. J362 is the ECU The "a" connection then continues to S4 fuse, which also powers injectors. Makes me think if someone connected it right to the 15 lead to bypass the immobiliser (not sure if it disconnects just the fuel pump relay or disables injector outputs, too on the 1.6)

Thanks for upload. Definitely gives an insight to my Issue :) The file can be opened in Excel. Here's what I put together after a quick look. Starting at timestamp 417.51. The first column is throttle valve angle, second is engine RPM, next is specified and actual boost. The actual boost value follows specified boost, except for engine speed under 2000RPM. Does it correlate with how the car feels?

If it helps, I found someone who logged their TSI here The OP also had some issues, but claimed that during the logging, the engine worked fine and values look OK.. so it should provide some data for reference.

I can't give you PNs, but there are several things different on the engine itself: Pistons (higher CR) Camshaft (different profile, different bearing size on majority of engines, which also means different timing chain sprockets) Head (7mm valve stems, conical springs, though this is not necessary So it may be easier to just get the entire donor engine. Regarding the knock sensor boss, I think that 136M actually has it in different place (closer to the gearbox, above reinforcement rib), unless there were some 136Bs from transfer period.

@Breezy_Pete Hello, I stumbled upon this topic. Have you been able to get some data from this? Looks it may be the culprit of my issues, some data would help greatly. How exactly did the car behave before the change and has the problem been resolved?

So the service had some time to take some measurements and was able to replicate the fail. Apparently the turbo only pushes around 1.3-1.5 bar absolute in 2000-3000RPM when specified pressure is around 1.8. full pressure is only reached beyond 3000RPM. Wastegate actuator position seems to correspond with driving voltage and changes in specified pressure, but I noticed that at some points, voltage goes above endpoint setting and the actual position goes negative. If I understood it correctly, 0 should be fully closed wastegate, right? Or is there some extra range on these engines and the wastegate never really shuts off? Also, what is normal voltage range with wastegate shut on these engines? On mine, the endpoint adaptation is at 3.8V, but when it goes negative, it goes up to 4.2V. I'm asking, because my turbo is the older type, with 2mm spacer fitted between the actuator and its mount. From what I could found on forums, this spacer changes endpoint voltage from ~4.2 to ~3.6V, so this could mean that something wore enough to make the spacer ineffective? But why didn't ECU adapt to this wear then?

Looks like charging is fine. After deleting the faults and driving until the issue reappeared, only the P155A error persisted. Could it be anything else besides the wastegate actuator and turbo itself?

Thanks, I'll check it

You reminded me - the battery died shortly after this happened for the first time. But it was still original from 2012, so I didn't think much of it. However, new battery didn't fix the issue.

Hi, hopefully you won't mind my question here - I don't have an Octavia, but its close relative from a Spanish brand. But mechanically, they are same. Anyway, I have a 77kW CBZB. It worked flawlessly for the year I own the car, but when this summer started, I noticed occasional loss of power. It only happens in hot weather (around 30 degrees and up) with AC on. In most cases, it happened when I wanted to accelerate after mild climbing at lower gear at ~2000RPM. It feels almost like a limp mode, but no check light and I can still somewhat accelerate to around 60mph. Observing fuel consumption, it drops from 11-12l full throttle on 5th gear to around 9l/100km, so between 20-30% of the engine power is lost. Diagnostics have shown code P155A and P0299. That would suggest turbo regulation, but that's usually accompanied with P334A/B/C error. Also, it's weird it only happens in hot weather with AC on. When I tried to replicate the issue, without AC, it didn't happen even in the recent heatwave. Anyone can point me in the right direction? I don't want to just start swapping parts without proper diagnosis of the issue. Also, what's the difference between P155A and P0299? Both point to under boost issues, but it seems they are triggered by different problems. If anyone explained me what are conditions for these issues, it would be very helpful. Thanks in advance!

No 21. 6U0121038 for non-ac 6U0121051F for AC Each is paired to a different pipe no 27, AC version wraps around the oil filter to clear the accessory holder. No 29 appears to be heater matrix output hose, that returns to the #27 pipe from the rear.