I will try to answer this question. Immobilizer on some VAG ECUs can be permanently disabled in DFlash (EEPROM) for WFS4 and early WFS5, which should be your case as well as I believe EDC17C46 is TC1767. Later WFS5 (with SHE hardware, like TC1793 - EDC17C74) are using different structure of DFlash and I did not saw any permanent solution, but it is still possible to patch those in PFlash (Program) to ignore immo state. It will create DTCs in memory, but ECU will start the engine nevertheless.
The cluster should contain master keys for immo (Sometimes it is BCM, sometimes other units) and you should be able to see encrypted communication between cluster and ECU on 0x10 / 0x11 CANIDs or when you have only ECU, then you will see only 0x10. So technically you don't need cluster, if you are able to disable or suppress the immobilizer in ECU.
Gateway is necessary, because there are several CAN networks, and cluster is on different CAN than ECU, so GW is routing messages from one CAN network to another.
Communication on CAN is described in so called DBC files. You can find some VW PQ files on
https://github.com/commaai/opendbc and you can open those in CANdb++ (tool distributed with Vector CANape or Vector CANoe, you can get demo from Vector for free). Also you can use Busmaster
https://rbei-etas.github.io/busmaster/ which can import DBC file and translate you CAN messages realtime into signals. You will need PeakCAN hardware for that (or Vector hardware if money are not the problem).
You can also use DBC files to emulate signals to ECU and get it working without real ECUs. When you know which signals are necessary and which are not for running of EDC17C46, then you can build some CAN signal emulator based on some MCU, which will keep EDC17C46 satisfied and running without other ECUs.
Thanks for the response.
Reasonably familiar with trawling through DBCs and doing it without expensive tools, using SocketCAN (gs_usb) devices and the pretty generic linux tools that go with.
The real question is whether I _need_ the gateway - if whatever signals are required I can dump onto PT-CAN (not sure of the name in VAG world) then surely the gateway is redundant at that point, unless the gateway has some say in communicating with other modules for starting, although I suspect putting 12v to the starter solenoid will cause the engine to run at that point and it's like push-starting it. It's things like the clutch switch, vehicle speed and others which are required as they will drive like shit without them, with a plan in future to send the right frames for cruise control to operate.
Just disable immo.
Everything will work.
You can use my tool for logging and live tuning, so you're really not missing out much compared to a standalone and gaining a huge amount by having the correct calibration.
Reason there's so little out there for Diesel is because you can't just calibrate the injection timing and pre-injection in a shed. Serious knowledge is required so it does not run like shit.
Thanks for that - yes, your tool is the only reason that this is remotely possible. I could run other ECUs, but with VehiCAL, it's worth it to use something VAG which has full A2Ls, FRs, high-speed logging and live tuning for a fraction of the cost with significantly greater functionality and the vast majority of the work done by the OEM. It's preferable to do it this method rather than any standalone, the final hurdle for me is using those ECUs out of the vehicles they were intended for.
I've experienced the pain of calibrating diesels from (essentially) scratch by building engine combinations that were not available from the factory thus no calibration to use and going through the process by having to flash every version, particularly getting the cold start calibration right. Torn out my hair for many hours even with combustion pressure monitoring.
