Why does the BMW 5 Series not respond when starting after wading through water and shifting to neutral?

[GriffinMarie]

BMW 5 Series not responding when starting after wading through water and shifting to neutral is caused by water entering the engine, leading to circuit failure. Engine water ingress situations: Generally, engine water ingress can be categorized into three scenarios. The first is engine submersion, which does not damage critical components. The second is minor water ingress, where the engine can still start normally. The third is significant water ingress into the engine cylinders, preventing normal engine startup. Different levels of water ingress will manifest different symptoms in the engine. Precautions after engine water ingress: Do not restart the engine after stalling. Automotive maintenance experts warn that during heavy rainfall, many roads may have deep water accumulation, and drivers should be cautious about the depth of standing water. If the water depth exceeds 20 cm (some high-clearance vehicles like SUVs can handle up to 30 cm of water), avoid driving through it. This is especially true for older models, where lower intake and exhaust ports can allow water to be sucked back into the engine through the exhaust pipe, causing stalling. When driving through waterlogged roads, use a low gear and proceed slowly. A crucial reminder: never lift off the accelerator when crossing water, as doing so creates strong suction in the exhaust system, potentially drawing water back into the engine.

[SanAbigail]

I've been driving for over a decade and often encounter post-flooding malfunctions. When a BMW 5 Series fails to start, common causes include sensor short circuits or ECU damage after water exposure. When water levels rise, the crankshaft position sensor under the car may get flooded, causing signal failure and making the engine misjudge its position during startup. Water-induced short circuits at wiring connectors can also cut off current, with blown fuses being a frequent occurrence. I recommend immediately checking the dashboard fuse box for start-related fuses—replace any blown ones. But avoid forcing ignition to prevent circuit damage. BMW's electronic systems are precision-engineered; water exposure exceeding 30cm can cause issues. Have it towed to a service station for diagnostic equipment checks—DIY repairs are risky and could cost thousands. Always drive slowly through puddles, detour around deep water, and prioritize safety.

[VanessaDella]

My BMW 5 Series had the same issue—it wouldn't start at all after driving through water. A friend mentioned it's due to sensitive electronic systems; water can submerge sensors or wire connectors, causing a short circuit. When the Engine Control Unit (ECU) encounters water-induced short circuits, it locks the system to prevent further damage. Blown fuses are also common, especially those related to startup. In my case, the fuses were fine, but the shop later found a faulty crankshaft sensor. BMW repairs are pricier, but their professional diagnostics are fast and accurate. If you encounter flooding, don't panic—first turn off the power and attempt a restart. If that fails, stay put and wait for assistance. Daily driving tip: avoid water depths exceeding one-third of the wheel height. Even with BMW's solid chassis, its numerous electronic components remain vulnerable to water damage.

[VanSkylar]

Failure to start after wading is mostly due to electrical issues. Water entering sensors such as the crankshaft or engine control unit (ECU) can cause short circuits, leading to system misjudgment. Water ingress in wiring connectors causing short circuits can also cut off power. Check the starter fuse in the fuse box; replace it if blown. However, if the BMW system is locked, you'll need to visit a 4S store for decoding. Safety tip: Do not force start, as it may cause more severe short circuits or engine damage. Quickly arrange for towing and repair.