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Help. Something somewhere is not right.

3K views 6 replies 3 participants last post by  DrFeelGood 
#1 ·
Hello everyone. This is my first post, but not a very good post. Am almost giving up. I am from Kenya in Africa, i own a 2010 Mazda Atenza GH series.
Issues. In chronological order.

I had charging issues, changed 2 alternators in a space of 2 months.

Autoshop said the alternators can not be faulty its my car making them faulty.
So i checked for the wires completely with my mech and we found out that the main wire from alternator has touched the belt (alternator, water pump belt) thus being eaten up slowly till the 2 wires from alternator came into contact.
This happened without a working alternator as i wouldn't buy another alternator without first knowing why 2 are already dead.

1 day later i buy new battery & ex japan alternator. Now here is where the rain poures on us literally.

We did put the 3rd alternator and the mech decided to check if its charging buy removing positive terminal from the battery.

The car just died, for 2 hours we tried to make even the dashboard to blick.

We found a blown fuse, we changed and the instrument cluster came back to life.

But almost all warning lights were on except engine oil and AFS.

So we checked all fuses and we found a ABS fuse blown, trying to put a new fuse it blows almost instantaneous thus we concluded the ABS module was fried when we took off the +terminal.

Did a scan of errors and we found Loss Communication with Abs, Steering wheel, Automatic Transmission, Low Charging Voltage.


Bought a new ABS module and the fuse now does not blow.

Problem for 3 weeks now is the warning lights are still there.

Check Engine
Power Steering
Abs
Handrake
Speedometer not moving + mileage
AT
Battery
Key knob.

Now the car runs like new, the only problem is power steering is abit stiff but its charging, changing gears, detecting when key goes out of the car but the warning lights are still there and you CAN NOT erase them using scan obd tool.

What might be the problem? Have taken to some good mechanic, tested can bus voltage, modules voltage and everything seems to be within rage. All mechanics agree its something small affecting the communication but nobody knows where to look now because if AT had problems gears couldn't shift, if not charging car could die on me,

I have a new ECU but not yet programmed with my key and anti theft so it can not work as of yet.

Fellow owners where should i start??
 
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#4 ·
Definitely get the new ECU in and see what happens. By the sound of things it seems like a massive short was caused by the alternator output wire. Considering the ABS module blowing it's fuse was not resolved until after you replaced it is not a good sign for other modules in the vehicle as well. The thing with these vehicles is that problem(s) in one module can trickle down to other modules causing other issues as well. For instance if your speedometer needle is not moving you could have an issue with the wheel speed sensor circuit or some other sensor related to speed. This would cause any other modules that need that data for proper operation to have errors. This is likely why even after replacing your ABS module the light still comes on. ABS absolutely needs wheel speed data to function properly. Power steering also needs wheel speed data to adjust the stiffness of the steering depending on the speed your going. I would expect the power steering module to possibly default to some failsafe mode if no speed info was being received (does the wheel get stiffer the slower you go?). This would of course cause the power steering light as well.

So you can see what I mean by this. The problem is you had such a catastrophic electrical failure that it could be beyond just a fuse that's blown in some of the modules. Some could be electrically damaged as well. I think replacing the ECU should at least help in figuring out what else needs replaced. I wish you the best of luck though because you may have yourself in a really troubling/expensive situation.
 
#5 ·
We have tested, all the modules for voltage, and can bus communication and all are ok. Its too confusing.
If its too catastrophic damage why is the car running like charm, i cover around 600km per week it does it very well other than power steering which to my conclusion is stiff because the ecu is saying the car isn't charging thus not powering the steering automatically.

My conviction has been change of ecu or reprogram it. Now i will do it and come back hopefully i have it fixed
 
#6 ·
CAN bus is a very robust protocol. It's almost unaffected by electrical noise and other electrical issues which is why it's so great and widely used in automotive applications. I can only guess here, but I suspect that while your CAN bus networks are still operating, there could still be issues with other modules attached to the networks causing them to not send expected information (like the messages containing speed). Keep in mind there's more than one CAN bus as well.

Why does your car still run? Well, it's entirely possible that the surge of current (if that's in fact what it was) did not effect the module(s) responsible for engine management. Electrical current always takes the path of least resistance, and that may not have been through your engine's ECU and thus it was spared. Or rather at least some of it's functionality was anyways. I don't mean to make a bad situation sound worse but let's look at your ABS module again. Whatever happened to your vehicles electrical system not only broke the circuitry in the ABS module, but also caused either an over-current or dead-short failure mode of the module itself. Module's like these are designed to withstand above-average electrical noise caused by the alternator and ruggedness from vehicle vibrations. Something really, really bad happened if an automotive-grade component died like that. It's not surprising you're still having issues elsewhere.

Anyways, while I can only speculate I still hope this info is of some help. Hopefully you'll be able to get it fixed!
 
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