I have a 2006 Pontiac G6. Yesterday our streets flooded from the rain. While driving my kids too school at 7:30am I drove through a large puddle of water that I didn't see. As soon as I got out of the puddle my car shut off. I got a boost but my car still wouldn't crank up. Everything in my car still comes on. I ended up having my car towed home. It has sat overnight & still won't crank up. What could be wrong?
How deep was the water? It is most likely an electrical problem with waterlogged or even shorted out electronics. However, if the water was pulled into the engine, you could have significant problems because water in not compressible and ingested water can cause significant damage to the moving parts inside the engine.
I'm assuming what you say the car wouldn't crank that means that the starter motor isn't trying to turn the engine over? It could be something as simple as the starter solenoid is still full of water. Knowing how deep the puddle was would help a lot.
Very hard to tell what's happened. If the intake got submerged under the water, you may have a water-locked engine. If so, pray to the god of engines that nothing is broken, take the HT-leads/coils out and then the spark plugs, and then try cranking the engine over a couple times.
If the electronics got submerged, wait for a few days for them to dry completely. Then, test again. If it doesn't work, go through a logical checklist; Starter motor, starter motor relay, starter motor fuse. Battery terminals, grounding to the bodywork, all engine bay electronic connectors, etc. Keep going.
Also, check your fuelling lines, too. That might have had water back-flushed through the return lines to the fuel tank or something else along those lines.
If the water was very deep and got sucked into the intake, then its possible that it can destroy the engine. Water is incompressible and if it makes it into the cylinder while running it can blow gaskets, or bend or brake your piston rods.
Ok it took me a while to figure this out about my 1997 Honda Odyssey but I ran through a water puddle. The car shut down and would not start so I thought I burned the starter out so I replaced it. Still, all lights would work but it would not engage the starter. I started looking around the engine and saw on the ground cable it was grounded to the body which made it possible for all the lights to work, but the starter would not engage. I followed the ground cable from the battery down to where it is grounded on the bottom of the engine and tada, there it was ... a broken ground cable. I reattached the cable and woooop, there it is, it started.
This may or may not help, but I did the same thing a couple of years ago.
Road service came to help and spent about 2-3 minutes jump starting my car constantly to blow moisture out of it. Lots of smoke etc from memory but once it finally started it was fine again.
I had a similar problem once on an older GM product where I ran through some high water. It ended up being the catalytic converter. The inside honeycomb of the converter seized shut when the cold water hit the extremely hot metal. A shade-tree mechanic solved my problem while a certified mechanic could not.