Sometimes, especially on cold mornings, my car won't start. The battery was replaced 1 year ago, and when i brought it to the mechanic, he said there was nothing wrong with it (he checked the alternater and the battery and said they were fine).

Have the fuel system pressure checked especially after you start and stop the engine. If the system loses pressure immediately, you have a problem with loss of residual pressure caused by a check valve or equivalent.

Could be the ( warm up 02 sensor)

That sounds like a battery issue. Batteries have whats called CCA (cold cranking amps) it is the main thing to pay attention to. This is a measure of how much current the battery can provide at 0 deg F. Batteries work better when they are warm, so the colder it gets, the less current it can provide.

Starting an engine requires a lot of current, over a very short time. Meanwhile, cold engines are harder to start, requiring more power to get them going. So look at your battery and its CCA and since u said u bought the car a few years ago. You probably didnt replace the battery yet have u? Batteries usually have a life of 4-6 yrs only. Hope this helped

You have what is called a parasitic draw on the electrical system , battery . Could be a control module not powering down when it's should . a electrical componet is staying on . , light in glove box , something you can't see . Bad diode in the alternator could cause this . But this just gussing , testing is the way to a fix . Watch thesed videos on testing for a draw on the system . Improved Methods to Find Parasitic Draw Battery Drains Overnight

The Trainer 27 3 Ways Of Finding The Cause Of Key Off Battery Drain...

just chiming in even though this is years old because i didnt see this answer. Theres a video on youtube and many equinox owners saying this worked.... clean the throttle body!

It could be the relay, But I don't think you have one, most starters are direct wired from the key to a solenoid on the starter, If there is a relay, it is the big fuse box under the hood, and is just a electric switch, not subject to cold. It sounds more like the terminals are filthy and the contacts are not connecting. Clean off all the wires with a wire brush and scrub the terminals with it, get underneath the connections too. Where the battery cables connect to the lead terminals, If I was up there I would be plugging in my car at night to keep it warm. It will start right up in the morning.

Check your battery for proper volts (12.6). Sometimes the cold weather will bring a battery down. Also check the Starter Relay, again cold weather will make it stick causing it not to start. Those are the biggest problems with a car not starting in the cold weather unless you have something else going on then your starter and your ignition needs to be checked.

YOU REPLACED BATTERY.BUT CHECK TO MAKE SURE YOU HAVE RIGHT COLD CRANKING AMPS.AND CHECK BATTERY CABLES.MAKE SURE THEY ARE CLEAN AND TIGHT.IF BATTERY CABLES OVER 10 YEARS OLD REPLACE THEM.MAKE SURE YOU ARE USING RIGHT VISCOSITY MOTOR OIL.YOU SHOULD BE USING 5W - 30 ENGINE OIL IN COLDER CLIMATES.IF YOUR OIL TOO THICK IT WILL CAUSE ENGINE DRAG WHEN CRANKING IN COLD WEATHER.

This could the problem with battery getting drain even if your car is parked , this could the problem in the wiring or the grounding in the car ,first check if any lights or the cd player has the power even if the car is parked ............................

Good luck...

Got that problem in my Accord 92, my sister brought it to the dealer
charged the battery and replaced the negative cable for the corrosion problem 300 $, drive it home till the morning after the battery dead once again called and brought to the dealer again now for 1,040 $ they will replace the battery, alternator and power steering pump no more money in my pocket so what I did is observed the reason why the battery die and die and die..found out that my cooling fan goes on without any reason, cold engine hot engine it will just run without any movement in the car tried to start the car dead battery i replaced the "Fan timer unit located under the driver side kick panel and voila for three weeks now no complain...hope this help!!!