New member, joined due to mystery engine problem. - : The site for all your Ford Mazda and Volvo needs
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post #1 of 3 (permalink) Old 12-06-2018, 02:23 PM Thread Starter
Bicycle Rider
Join Date: Dec 2018
Posts: 1
New member, joined due to mystery engine problem.

Sorry if this is lengthy, but I want to give a clear picture of the issue.

As stated in my topic heading, I've joined the forums owing to a car problem that our mechanic couldn't diagnose. I have a base model (no keyless entry) 2.0 liter Mazda 3, about 135,000 miles, not driven hard or raced. Strictly commuter.

Drove it yesterday afternoon to pick my kid up from school. Car ran just fine. Got my kid in the car, put my key in the ignition, and nothing. No crank. No electrics. No instrument panel. No security light. Zilch. Called my fiance and he drives over from work to help. We are sitting in my car discussing what action to take when the instrument panel starts doing the same thing as the panel in this video:

(Not my video! NSFW language warning for some swearing.)

After seeing that weirdness, we tried turning the key, but again, no crank, no panel lights, nothing.

Fiance hooks up jumper cables from his car to mine, runs engine for a minute, my car starts right up. We replaced the battery a month ago, so we decide to go down the road and get it tested to see if it's faulty. After unhooking the jumper cables, I do a few laps in the parking lot bc I have a sneaking suspicion it might die again. As I'm driving, the dials start going wild again, "Welcome" message on clock display flashing along with welcome chime, power steering cutting out and in. It does that about three times, then loses power and dies.

We hook the jumper cables up again and run his car for about 20 minutes. I try the engine again and the panel lights up, but beyond that all that happens is the starter cranks. We wait a little longer with the jumper cables running and try again. The engine starts okay this time. We unhook the cables and try to leave, but as soon as I shift into drive, the car dies again. No electrics, no brakes, nothing. Coasted into a parking space and pulled the e-brake.

We took the battery out and had it tested. Battery was fine. Had car towed to shop. Starter is fine. Alternator is fine. Battery is (again) fine. No codes thrown. Fuses are all fine.

The shop got the car to start this morning and they drove it around with zero issues. The mechanic is stumped. Thinks it might be the "ECU"? They said to take it to a Mazda dealer, but the only one in town is *not* honest. I've had big problems with them before and don't trust them to be straight about what's going on.

Any ideas? Is it the computer? Loose wiring? I'm afraid to drive it until this gets sorted out. Don't want to lose my brakes and power steering without warning!

Thanks much for any input!
Wombatmobile is offline  
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post #2 of 3 (permalink) Old 12-06-2018, 02:37 PM
Join Date: Apr 2018
Location: At the bottom of the California Sierra Mountains
Posts: 771
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Welcome to the forum..
If your mechanic is "stumped" you really need to take your car to a shop that has the ASE sign hanging employee's ASE Certified Auto Technicians (you can see how current they are on there certification that is usually displayed in the front shop area of mot service shops) and have them do the basic one hour testing and evaluation. They will find and tell you what is going on.

ASE are trained in the latest EFI/ECU vehicles and will have the proper Diagnostic scanning equipment. Most already had basic mechanical auto repair experience in electrical trouble shooting.

These day if you one any vehicle manufacture from 1995 and newer you can't really expect anything except a service shop that is up to the training and certification to trouble shoot your vehicle?

For what it is worth ... Before you start any diagnostic checking you should fully charge you battery ( it does not matter the age new or old) and have it properly load tested (the battery must be fully charged). Check all the battery connections at the battery and also the ground from the battery to where it is connected.

To help that first thing you should have posted is the accurate DTC's and state of monitors. Anything less then the first thing to suspect is the diagnostic connector , the ECU main communication harness or the ECU itself.

The dealership you mention I presume is an authorized MAZDA dealership and should be using the proper software provided for the MAZDA service department and will at least outline basic diagnostic testing. You can also ask for a detailed service report that shows what was done to fine any problems.

Last edited by M3RacerX; 12-06-2018 at 02:42 PM.
M3RacerX is offline  
post #3 of 3 (permalink) Old 12-12-2018, 12:48 PM
Moped Rider
Join Date: Dec 2018
Location: Black Hills of South Dakota
Posts: 34
Maybe clean all your battery cable connections. Easy and worth a shot. Unless they did that when the battery was replaced. Almost sounds like a grounding issue. Trace the ground wires. Verify their condition. Corrosion creeps in and makes these kinds of things happen. Not saying this is what it is but fairly easy to check out.
Xbeaus is offline  
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