If the engine stalls immediately after starting, it could be due to the activation of the vehicle's anti-theft system. When triggered, the system locks the engine, allowing it to start but preventing it from running. Releasing the key causes the engine to sputter and stall within a second or two, accompanied by the illumination of the anti-theft warning light. This issue is commonly observed in Volkswagen and Audi models, often resulting from the use of a non-chip key (made privately to prevent key loss) or a key with weakened signals due to physical damage, which the system fails to recognize. Additional relevant information is as follows: 1. Ignition switch malfunction. During startup, the ignition line receives power, but releasing the key cuts off the power, causing the engine to sputter and stall. This is typically caused by poor internal contact within the ignition switch and is often accompanied by issues such as the dashboard battery light, oil light, or engine warning light not illuminating. Some vehicles may intermittently experience failures like no AC/heater, headlights not working, or malfunctioning power windows before the problem fully manifests. 2. Damaged ignition module or faulty ignition reference signal line between the ignition module and the engine control unit (ECU). This issue is prevalent in American vehicles, particularly Buick models, due to their unique ignition system control method. In simple terms, during the initial startup phase when engine speed is below 500 rpm, the ignition module controls ignition based on signals from the crankshaft and camshaft position sensors and its internal data. Once the engine speed exceeds 500 rpm, control of ignition and fuel injection is transferred to the ECU, which integrates inputs from various sensors and the ignition reference signal from the ignition module for comprehensive control.
