My son has an automatic, 2008 Mazda 3 GT hatchback. It has about 134,000km. In the last few weeks when it got really cold (like to -45C), he went out to start it after work and it wouldn't crank at all. Turn the key, nothing, but all lights, heater, etc work fine. It was plugged in, so he tried boosting thinking it was the battery (which is less than a year old, quality Kirkland battery...8 year warranty, 650CCA). It wouldn't crank even with an engine boost. I told him over the phone to try wiggling the key, he did, and it started. Started fine for a few days, then wouldn't start again. The 'red key' would start rapidly flashing on the dash after turning the key to on after a few seconds. I switched the main/heater/starter relays around thinking it may be a relay, no luck.

Had it towed to the dealer thinking it may be a key/alarm issue (has the factory alarm, remote start). They put it in the shop, warmed it up, and were able to boost it to start it, so they told us it was the battery. That made no sense, so I had the battery tested rigorously at P.A. Battery (printout and the whole deal, manually tested every cell). They said the battery is like new and the dealer is wrong...big surprise. Still not able to start, so towed it to a mechanic I trust. They ran a wire from the starter relay and were able to start it no trouble when touching the wire to the positive post on the battery. No matter the temperature, starts every time. So, it's not the starter, relays, fuses, and I'm assuming not an issue with the transponder reading the key.

Now though the red security light was rapidly flashing all the time (running or not) on the left side of the steering wheel. My son didn't have his other working key fob, so he went and got it, clicked the unlock button and lock a few times, and the light stopped flashing and the car started right up. The car had been in the garage all day at about -5C (vs -24C outside). We thought it was fixed, but today after the car sat outside in -41C all night (plugged in), it wouldn't crank over again. Touched the wire to the + battery post (key in the 'On' position), fired right up.

So I'm down to thinking this is an electrical short/connection issue somewhere, a bad ECM, or maybe a faulty ignition switch/tumbler issue? Could it be the solenoid on the starter? Would touching that wire to the post bypass that? I should mention there is a generic U0100 code (communication with ECM) that has been on for over a year now. I read it with my ODB2 reader, clear it, and it comes right back. Any ideas before I just tell him to get rid of this Mazda and never look back?

EDIT: We've narrowed it down to a temperature issue. When the car is warm-ish (i.e. -10C plus), it starts fine with the key. Any colder and it won't start without using the bypass wire. Are frozen relays still a thing even in the 2008 Mazda? I've switched the starter relay out with the heater relay as they are the same (as is the MAIN relay). We'll see what happens after sitting outside tonight in -26C...

 

I don't want to keep adding to my previous post, so I'll reply to myself I guess! For anyone having this issue, I've solved it, no thanks to the shop or the useless dealership(s). The problem is the ignition relay. I switched the heater and ignition relays around and it starts, but the heater doesn't work in anything colder than -10C (it's -12C atm). Switch them back, no start (without jumping to the battery) but the heater works now. So Mazda obviously still has issues with relays freezing up, no matter what the 'expert with 30+ years in Mazdas' told me at the dealership. Supposedly they fixed the issue after 2006, but that is obviously false. In my '30+ years of experience' with almost all brands of vehicles in cold weather, I have NEVER run into this.

Why did I not do this right off the bat? Short story, I did, but his alarm had activated itself, and he didn't have his one working key FOB with him (he was back home from University over the Xmas break). I tried every procedure out there to disable the alarm (locking the doors twice, turning the key forward for 10 secs and back, etc.) and nothing would disable it except the FOB. I don't know enough about these factory alarms (or any alarms, as I try to only buy older vehicles without all that crap in them), and I didn't realize you MUST have the FOB in order to disable the alarm. How convenient for the dealerships.

Anyways, I hope this helps someone else that runs into this issue down the road. It certainly would have saved me a lot of grief and my son some cash...

 

Just curious that during all this no start you never had any DTC(S)??????

 

No. As I said, there has been the UO100 code for almost 2 years, but nothing else. You clear it, it comes right back. It's so generic though that it tells you nothing. The Mazda dealer did their full check on the computer system when it was in there, or at least that's what they told me. I'll see if the code comes back after putting the new relay in.

I didn't want to get sidetracked, but he has had a new (salvage) engine put into this car. He had it only about 8 months and the head gasket went at 110,000km. Again, I've never had a head gasket go on any vehicle, even my '99 Sierra 2500 with 300,000km now. Morons at that shop told us it was just a coolant sensor malfunctioning, it wasn't actually overheating and it was perfectly fine to keep driving it. They actually typed that on the receipt. I called BS on that as it was clearly still overheating. Ended up warping the head and he needed a whole new engine (or I should say it was cheaper just to get another engine). Thankfully salvage had one with low km in nicer shape than the one he had in there. I thought about suing them, but this isn't the US . Anyways, my point is that the same code was on prior to the engine going out.

If you think all this has soured me on ever again buying a Mazda, you'd be correct! Unfortunately this was his first car and I can guarantee he won't buy another one either.

 

Ya ..so yes that does help. And clearing it only resets the check engine light it does not correct the issues if it is in RAM and holding. You can check the monitors which will help to narrow down a diagnostic plan to begin resolving the issue. Sorry, that you seem to get Mechanic's" that are not trained and certified Automotive and or Factory Technicians in proper Diagnostics trouble shooting!

I realize it appears that your battery was ruled out of the problem........ at least from your information?
Just an FYI the battery date of manufacture is not the same as when you purchased the battery, and the little tag is not when the battery was manufactured. So, looking at your invoice or the tag is not a good way to say how old the battery is. And regardless it is not ever an indication of the battery's health.

Suggestion at this point if the MAZDA is out of warranty of any kind look for a service shop with a current ASE Technician. Shops will generally advertise this as it does require training and testing to acquire the certification of which diagnostic trouble shooting is a big part of it considering most all gas-powered vehicles (1995 and newer) are currently OBDII.

 

It's 14 years old, so definitely quite out of warranty. As I said in my first post, I had the (less than one year old) battery rigorously tested at a reputable place in town here that ONLY does batteries. They took me to the back and I watched them do it. They provided me a printout of the load test and confirmed the CCA. He also individually tested each cell with a hygrometer and they were perfect. They didn't try and sell me a battery...unlike the dealer. I've been buying Costco (Kirkland) batteries for almost 20 years as they have an 8 year warranty and are made by Johnson Controls. I have one in my truck, had one in my Pathfinder that I sold last fall, and also have one in my Kia. If you can't tell from the sticker or date code stamped on the battery, how exactly are you supposed to know when the battery was made?

I've never had any issues, other than one that I probably let sit too long in the winter (several months) and it wouldn't hold a charge, but it was 7 years old. I took it back to Costco and they gave me $45 cash back for it...after 7 years. I also didn't mention it, but we went to Canadian Tire (highest volume battery sales in the entire country), bought a brand new 4 year warranty battery and tried the car. It still wouldn't start, nothing changed. It's not the battery.

The mechanic that misdiagnosed the head gasket was a 'get into a shop at the last minute because he needs his car' type thing, so not a shop I knew (my son lives 1.5 hrs away). I'm not sure it would have made a difference honestly as it's hard to know when the damage was done. A head can get warped real quick with superheated coolant spilling on it. The Mazda dealer I took it to has a current ASE technician...he made that very clear when I started to question their competence . No need though as I figured it out on my own.

 

Ok well you will find a shop eventually that knows what they are doing.
The ECU really works well to report in advance possible problematic areas.
The monitors will not be in "READY": state until all condition is within operating perimeters.

General battery info.
Batteries unless they state are 100% brand new material are generally now manufactured from recycled material.
This does and has affected the longevity and performance of many batteries with trusted branded names now.
The manufacture date code is usually melted in the top lid side often very overlooked or by most never noticed on the battery. It is coded and unless you know the different codes used by the manufacture (not the distributor) then you need to go to the "manufacture's website and look for that information to decode the manufacture date. The shop you had the battery tested isf they are really worth their salt knowing batteries could have told you the true age of your battery.
Another thing those stickers are often replaced as batterie's are rotated in stock by a distributor when tested to still be healthy. This is why I always recommend when buying a battery at a location but not online is to look for the newest date code sticker. This way you at least have a somewhat assurance that the battery was recently tested.

 

I just don't want to take it to the dealer to have them figure out the root cause of the code as I'm sure that will result in an astronomical bill, and likely no solution. I'm also not inclined to spend $1,000 more trying to find a shop that can figure it out. May as well just start replacing parts instead. Unless it's causing a problem, it's going be on there until he sells the car (probably when he's done school). The code may stay off once the relay is replaced.

The relay was quite difficult to find and I ended up having to go to the dealer. It's being shipped from Vancouver, but they were actually the cheapest at only $19. Odd that it's out of stock everywhere as that same relay is used in a lot of vehicles. If he would have had his working FOB with him, it would have cost him a total of $19 as it took me all of 3 minutes on Google to know to switch the relays. The dealers must not have google?

On batteries, that's why I buy from Costco and don't worry too much about the absolute accuracy of the date. With their return policy, and high turnover rate of batteries, I can't really lose.

 

The biggest mistake "people" (mechanic's included) is to start replacing suspected parts without verification of fault. This more than often times creates added problems.

Good luck with your MAZDA!

 

Yah, that's why I didn't start doing that, but in this case, replacing a $20 relay would have saved him $350 dealing with morons. Although I 'did' verify the fault, the car was just locked out by the alarm for whatever reason.

EDIT: -13C today, car wouldn't start. Received the new ignition relay and installed it, car fired right up, problem solved, frozen relay.