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Car shuts off while driving; no code

Twice now, my ex-wife’s 2009 Civic Hybrid has simply shot off completely while she was driving it, as if the key had been turned off. Both times, the dealer says they can’t find anything wrong and no codes have been recorded. After the first time, I replaced the ignition switch (not the lock cylinder but the switch that clips to the back of it). This is very scary when it happens, because the shutdown is complete and with no warning. Has anyone heard of anything similar?

Well, the first thing I thought of was the ignition switch since a failure would make the car think you’d turned off the key, and therefore it wouldn’t store a code. So, good thinking on your part. Assuming the switch you replaced it with is not DOA (and that’s not always a sound assumption), it’s time for more diagnostic work.

First step, check the battery thoroughly. Make sure the wires are tight and clean, both where they connect to the battery and at the other ends. And make sure they’re unbroken and that the insulation is good throughout their length.

The next time this happens, she should immediately honk the horn. If the horn fails to sound, you are losing power to the vehicle. This would also not store a code because there isn’t any power to the computer that should be storing a code!

If all the wiring is good, then my next step would be to replace the battery. The battery posts can break internally. The only symptom you get is that the car loses power completely from time to time - there’s no visible indication from the outside of the battery that this has happened. And even if you take the battery in to be tested, unless you get lucky and the post moves just right so that the break separates the two sides at the moment it’s tested, the battery will test perfectly fine.

A faulty crankshaft position sensor will cause a car to shut off with no warning.

Then if you wait long enough, the sensor cools down and the engine starts/runs again.

https://www.rockauto.com/en/catalog/honda,2009,civic,1.3l+l4+electric/gas,1444068,ignition,crankshaft+position+sensor,7196

Tester

Those are both great suggestions. And honking the horn after shutoff will distinguish the two. She lives in a different city from me and the problem takes months to recur, but I’ll pass the information on. Thanks!

To the good advice offered here so far, I’d add that there are probably some Honda hybrid-specific discussion panels that might offer help. Others may have experienced the same exact syndrome and found the solution.