Car starts and dies immediately

Hi, new to the forum and have a question. I have a mk4 golf 2000 115 gttdi! It starts up but then dies immediately. I know that the common issue for this is the immobiliser so it has now been mapped out of the ECU but it still does the exact same thing. The immobiliser light does not show on the dash and was doing this prior to it being mapped out. Any suggestions?

Check for fault codes via vag com

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Agree with that - needs a scan at the least.

Has the ignition switch ever been replaced? You need to check the feeds from it - voltmeter at the ready.

Replace the Main power Relay 109 Main power relay this causes your described symptoms and many more.

Relay 109 supplies power to: Relay 109 VW Part NO: 1J0906381A - Glow plug relay - Fuse 32 ECM Fuel quantity adjuster - Fuse 34 Cold start injector Waste gate bypass regulator valve (N75) Change over valve (N239) EGR vacuum regulator valve (N18) Mass air flow sensor (G70) - Fuse 43 Clutch vacuum vent valve (if equipped) Brake vacuum vent valve Relays for preheating coolant (if equipped) Crankcase ventilation heating element The ECM supplies power (and sometime ground as well) for: Fuel cutoff valve Cruise control switch Manifold (intake) air pressure/Intake air temperature sensor Needle lift sensor Engine speed sensor Engine coolant sensor Closed throttle position switch (part of "go" pedal) Kickdown switch (part of "go" pedal) Throttle position switch (part of "go" pedal) Fuel temperature sensor Modulating piston displacement sensor The ECM also communicates to the instrument cluster electronics and transmission control module (on automatics). As a result of this, you can see why if the relay starts to cause power to flicker, or voltage drops, for all of these components, the results can be "unpredicatable" and none of them desireable.