Breezy_Pete

Check the engine-running voltage across the battery. Brightness of incandescent bulbs goes up with the square of applied voltage, so you would prefer not to have a lossy charging system.

Is the engine speed sensor (crank angle sensor) something that has been checked or replaced?

That part number can be relied on. Thought it might help. Having said that, the ETKA page also says "Before parts order, physical inspection of old part necessary" So yeah, leave it to the people who'll do the work.

Your reg number gives this part number for the flywheel - 028 105 269 B Judging by the image (if representative) on this page, I think that isn't dual mass, but I'm no expert. Flywheel 1.6TDI, 1.9TDI Sachs 028105269B

As expected, left rear door has only single LIN-wire comms with left front door, via pin 19 at the B and A-pillar connectors respectively. It's a lilac/white wire. Fuse (32) that covers rear left is shared with rear right, so if rear right door is OK it can't be that. Front left door has CAN bus connections into convenience system, is that (front left door stuff) all working fully? If so I think the LIN wire to rear left, or an earth at rear left door seems the most likely problem. Will PM you the relevant pages of circuits.

Will have a look in the morning for you.

Reg number or VIN would help. That would give me build date and options, which will affect which wiring diagram is most appropriate. I have a feeling it'll show that the rear door module is in communication with just the front door module on same side of the car via single wire LIN bus.

If it's RHD, I'd suggest checking wiring to left/passenger front door for wire breaks.

LHD or RHD car?

Acquired a similar vehicle myself recently, a 2007 and manual transmission but otherwise equivalent. Liking it so far, but lots to learn. @ColinD should read at least your first paragraph @dsolds.

Is there something in particular that you are trying to find? Wiring diagrams have two sets of J519 pinouts for cars built in 2011, one set covers cars built up until end of April 2011, the other set from May 2011, not sure if that coincides with the pre/post facelift timescale for Yeti.

The throttle body on your car is connected only to the engine ECU. The engine ECU has no permanent connection to 12V, it is only powered when the ignition (contact) is on or engine is running. So if it is making noise when the key is not in the ignition, there is a fault with the car's electrics, not the throttle body. I think the ECU relay would be my first suspect, perhaps its contacts are sometimes welding themselves together. This relay is in position 12 of the relay carrier in the cabin. The emissions problem may be a lambda sensor being too old, or possibly the catalytic converter. Or if you still have not checked cylinder compressions, then it may be an exhaust valve problem.

If it's the factory fitted original unit, you won't need a code.

Well done. Any sign of damage to the wires coming out of the other connector, the one that you unplugged it from?

No compression figures yet? The 1.2 HTP engines, especially the 6-valve version, are infamous for burning their exhaust valves. No amount of new plugs and coilpacks can help if that has happened.

Your 'pressure difference sender' has part number 059 906 051C. Check search engine results for images thereof. Have been known to suffer heat damage. Fault codes would be helpful though. How many miles has it done, and what's the typical usage pattern (lots of short trips?).

Exhaust system will have a bit of a littering of sensors including about 3 temperature sensors, so I wouldn't be able to readily identify the one you are describing.

Skoda dealers have an RRP of £233 + VAT for the lambda sensor for your car (same part number as in LLL link) so you definitely don't want to be buying one of those from them without very strong evidence it is at fault! I've never heard of one being discussed in the context of DPF regen problems, to be honest. Will look up pressure sensor info later, just about to hit the road for a while. Try to grab some fault codes with VCDS.

I can find VIN from reg, so that's enough info. 👍

One differential pressure sensor only, I think, with one hose connection upstream of DPF, and with it's other connection downstream of DPF or left open to atmosphere (because exhaust pressure after DPF is naturally close to atmospheric). Sensor may be visible near top rear of engine bay if you can pop a photo up. The 'Fault codes' button when connected to control module 01 (engine ECU) should give you any stored codes. See first three images here: Guide: Check Your ECU/TCU Box Code & Software Version - Audi/Volkswagen Fault Codes button just under where it says Basic Functions in third image.

Could you please clarify the age of the car? You have CAYC as engine code in the thread title, but 2017 as the year in your profile, which would be a mk3 Fabia, and probably not a CAYC. Reg number or VIN would help me to offer definitive part number info for any given sensor.

Lambda and oxygen sensor are interchangeable names for something that measures oxygen content of the exhaust gas. This may be used to fine-tune the combusted mixture in a petrol engined car, or to help control various emissions after-treatment kit in a diesel engined one. Exactly how the lambda sensor in a CAYC is used isn't something I know. Differential pressure sensor is sensing the pressure difference upstream to downstream of the DPF. This can be used to infer the 'fullness' of the DPF. Genuine VW group sensors can be spectacularly expensive. Be happy that your car probably doesn't have NOx sensors, they would be a lot more. As for how to proceed; you say but is VCDS picking up any stored fault code numbers, and if so what are they?

Might be wires shorting at the cable entry of the thermoswitch connector, rather than one of the switches being welded shut. Which you've now disturbed and cleared the short? It is a horrible spot for access, and the connector latch is probably facing in an unhelpful direction. Last time I was in that area on a 9N3 Polo I used to own, the wiring just outside the thermoswitch connector was a right mess.

Good progress, try thermoswitch 3-pin connector out next, then reconnect 6-way.

That schematic ^ doesn't include the 12V conns of the 6-way or the K1/K2 ones, let me find a page showing those, for completeness.