2010 Mazda 3 won’t start

Asked by Phoenix273bm Mar 02, 2020 at 11:28 AM about the 2010 Mazda MAZDA3 s Sport Hatchback

Question type: Maintenance & Repair

Please help, I’m at a loss,... Ive tried everything I
can think of. .... consisting of: 2+ weeks at
dealership, over 1000$ in parts/labor and over
30hrs of my own time trying to fix it. Nothing fixes

My wife has a 2010 Mazda 3 hatchback, automatic,
2.5l.  The car basically “forgets” it’s in park when
sitting overnight (or long periods of more than 3-
4hrs) and therefore wont start. You have to either
wiggle the shifter (25% of time) without switching
gears or go from park to neutral and back to park
(75% of time) .... then it remembers, and it starts.
By “forget” I mean Electronically doesn’t recognize
and doesn’t light up the green “P” indicator even
though mechanically it is in park. So it doesn’t think
it’s in park, so it won’t let you start it. Once it runs, it
runs fine. No issues. Shifts through gears perfect.
No codes on any reader. Goes into park fine (lights
up). Can be re-started if it’s less than an hour or
two. Like no issue at all. Then leave it overnight and
problem back next morning like clockwork.

I’ve tried all usual things to fix it, and Every time it
works for either a day or two and it returns. Or not
at all. So far I’ve replaced/adjusted:

Neutral safety switch (3x actually, incase I got bad
ones and both aftermarket brands one from
autozone one from oriely’s and one for action auto).

Dealer-replaced the lever, nut and washer coming
from transmission. Per some service announcement
on an older model. It was corroded at time. That
lost me car for two weeks while they ordered it.

Brake-Pedal sensor.

New battery. (It was 4.5 years old and one day it
was dead in morning, no obvious sign what drained
it. Just opted to buy brand new one due to age,
been fine for a month since. No issues).  

Adjusted the shift cable Multiple times. Adjusted
the neutral safety switches multiple times. Cleaned
connection clips.

I just finished replacing the entire shift cable. And
the bracket that holds it to the transmission (in case
it was bent or internal corrosion). Ordered both
OEM from Mazda dealership but put them in

Cleaned little black switch inside shifter housing.
(Tiny metal flap that has two small wires. Can’t
reach it since 8mm bolts that hold panel spin but
don’t come out. But cleaned dirt and discolored
grease off. Makes a faint clicking sound when car
goes into final park. Not sure what this “does” but
I’m desperate).

This problem has been going on for 5+ months. So
annoying. And I’m literally out of ideas. Anyone
have any possible causes?  I can’t find anything
else on internet.

P.s. I did see one for a manual transmission said it
was a corroded wire into starter, but that doesn’t
seem to be issue on wife’s car. Wire seems fine and
car does start no problem once it electronically
knows it’s in park and can.

4 Answers

If that would help ... I would, turns out Though, sarcasm (Or swearing are it) doesn’t fix the problem, I’ve tried those options too.


It almost sounds like the transmissions ECU is faulty. I wonder if you could swap out (if it's separate) not sure on that - with a another used one. Junk yard maybe? Sounds like an electrical gremlin. Something is getting hot and shuts down after heat soak or run time.

1 people found this helpful.

Yeah, it’s very random issue. Like last two days it had been raining and car started just fine, even in morning. Now that it’s dry, issue return mid-day for first time When wife went for lunch. It’s very random. If it was corrosion you’d think it’d be worse in rain then dry. But she does drive about 2hrs a day with the vehicle. I’ve posted to five different mechanic boards. And although no one has ever seen/experienced this particular issue before, consensus seems to believe it is likely either a faulty ground connection (either inside NSS connection clip or the #7 ground attaching to the transmission for the TCM itself) or a faulty TCM. Definitely an electrical gremlin, as all the mechanical stuff is new and adjusted properly. The TCM is about $7-800; so isn’t worth it if the only issue is having to wiggle it to make it remember it’s in park.

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