Hi there,

New member so be gentle with me ! :-)

My otherwise ultra reliable Mazda3 has decided to let me down. It's my fault I know. I went away on holiday and didn't take 3 with me. And now I've got to pay the price for my negligence! :-)

To cut a long story short, I was away for several weeks, and the battery went a bit low. I could tell because when I went to open the doors the actuators sounded really sluggish. I decided to charge the battery overnight before trying to start the car. Next morning, the doors unlocked remotely normally, but I couldn't start the car. All three keys are the same.

When I insert the key into the ignition, the dashboard lights up as expected, but the padlock LED starts to flash rapidly (and never stops). When I go to turn the car over, there isn't any noise at all, in fact the LCD display for the radio etc goes off. Quite a few other LEDs remain lit as well, but I don't remember if this is normal till the car turns over (hot and cold thermometer icons, ABS, side lights (even though they are off), Check Engine, anti-skid (ECS), oil, airbag, battery, parking brake - which is on.

I have 3 unique keys for this car, and I've had them all tested by a local car electrician, and he says they are working normally. I called an auto locksmith out, but he determined that there is a car fault, and not an immobiliser fault - but I'm not so sure. He checked all the fuses and said they are OK.

I've read other posts which say that when the immobiliser activates, the main PCM or ECU stops responding, giving the impression that there are multiple faults. I was also told that the immobiliser rarely causes an issue because it's based on Ford system which doesn't use a rolling code.

I've tried loads of different key resets found online, none of which have worked.

Do I have to get the car to a dealer or is this something I might be able to resolve myself? Any help or suggestions gratefully received, as my nearest dealer is a considerable distance away.

Thanks in advance for any suggestions or advice.

MJ

Mazda3 2010 1.6 Sport

 

Welcome to the forum

Regarding any electrical issue the first thing to have checked is the batteries condition. This really can only be effectively done with a Load Test.
Charging the battery is not an indicator nor if it reads 12+ volts of it state of condition only measuring it voltage.

Jumping a battery or charging it does not cure a failing battery.

The other suggestion is that if you must remove the battery to confirm that all 4-battery connection are clean and making good contact. on the battery terminals then the ground cable and the start cable.
If you do remove the battery and replace it make sure to do the CORRECT cable installation. Failure to do that can cause damage to the electrical system


The next item to check is your ECU/PCM using a diagnostic scanner connected directly to the diagnostic connector. (no blue tooth devices)

 

Thanks for the reply.

The battery is definitely OK.

No one (including myself) has been able to connect via the OBD2 port, using three different wired ELM237 scanners. There are absolutely no signals on pin 2 or pin 10 of the OBD2 port.
There is a reference +5V signal at the MAF, but not S-Start voltage at the fuse on the side of the dash (which would be correct if the immobiliser has kicked in).

I also found a post that discusses corrupt data in the ECU eprom, but that would require direct access into the ECU to reflash, something that I don't think a main dealer would allow.

The car has since been transported to a Mazda dealer, and I'm awaiting their diagnosis. I suspect it will be a new ECU, PATS sync, etc - which will cost more than the car is actually worth.

Will update this thread once I have more info.

Best,

MJ

 

As an update to this problem, it looks like a defective Denso PCM. I suspect the dealer didn't want to risk purchasing the part, as they dragged their heels before I gave up waiting and got the car back.

Looks like I'm going to have a go at cloning the ECU, or re-programming a used one.

Very dissapointing indeed.

 

The ECU is usually the last thing to fail. Powering it down by disconnecting it for a few minutes MAY help but worth a try before spending money. The ELM scanners. Well the OE chips are coded and the aftermarket don't work in most situations. The company did it to protect their copyright.