Mazda Problems

Most mechanics will do a complete check up and tune of the engine as part of tracking this problem and it’s a good start, because a new set of spark plugs and plug leads might just fix this problem. But that won’t always be the case. As such, you could be looking at a dud sensor somewhere in the engine bay that is telling the on-board computer to shut things down or, at least, not providing the computer with enough information to keep it all running. For this reason, an electronic scan of the vehicle should also be carried out at the same time to see what fault codes are cropping up.

A prime suspect for this behaviour would be what’s called the engine’s stepper motor which is a small electric motor that controls the throttle body and, therefore, the car’s idle speed. If this motor is maladjusted or faulty, it could cause the engine to either idle roughly, too slowly, or stall altogether. But have the scan done before rushing out to spend money on parts that may or may not be the problem.

There’s a very simple check you can do to see whether the battery or the charging system (alternator, regulator and wiring) is at fault here. With the engine running, place the probes of a multi-meter (switched to measure voltage) on the relevant battery terminals. If you see a figure of anywhere between 13.2 and 14.7 volts, the charging system is doing its job. You might need to rev the engine slightly off idle to see these numbers, but the voltage going into the battery should be in that range.

At this point, the battery becomes the main suspect, and a worn out battery will often neither hold a charge nor accept one.

The CX-5 is a well regarded vehicle in the trade with a good reputation for going the distance and remaining reliable. However, that’s a lot of kilometres for any vehicle.

Which means, you must approach this one purely on its individual merits. That starts with the service history. Unless you can find a complete, detailed record that proves the car has been absolutely maintained correctly, you could be taking a huge punt. You’d also want to learn as much as you can about who owned it and how it was driven. For instance, 300,000km of gentle highway running is a lot different to the same distance in city traffic or towing a trailer around.

Even then, it would want to be really cheap as you might easily find it’s getting very close to the end of its useful life. That said, a well maintained, carefully driven CX-5 can cover this sort of mileage, so maybe this one has some life left in it. Maybe.

In the old days, this would (probably) have been a simple matter of a faulty wiper switch. But on modern cars, functions like the wipers are controlled by a computer called the body-control module. If this starts to fail it can send odd signals to the various things it controls (wipers, lights, central locking, climate-control, entertainment systems and many more).

An automotive electrician might be able to pin-point the problem, and that’s a good place to start. But before you do that, try this: Disconnect the car’s battery and leave it overnight. When you reconnect the battery, you might just find the computer has reset itself and things return to normal. It can sometimes be just a temporary fix, but it’s definitely worth a try. And it’s free.

There does seem to be a bit of a trend here where the Mazda software won’t talk to its owners’ phones. It’s not just a Mazda thing, either; plenty of car-makers using proprietary software receive customer complaints when the software and apps won’t play ball.

Some owners have had success by disconnecting the car’s battery overnight and forcing a reset to factory settings, but in other cases, the refusal to operate correctly is intermittent.

However, it’s up to Mazda to make good on a fix for this. Whether that involves replacing the head unit and screen with a new one, downloading new software or a patch for the existing stuff or whatever the solution is, your factory new-car warranty should cover this. Make sure the fault has been logged at the dealership (so Mazda knows it’s a pre-existing condition) and don’t be afraid to tackle Mazda Australia’s customer service division to see what can be done.

You should be guided by your mechanic’s quote for either outcome. In some cases, solenoids are relatively cheap to buy and don’t require too much labour to replace. But, depending on the vehicle, they can also be very expensive and require more or less a full transmission strip-down to remove and replace.

You also need to assess the condition of the whole transmission as putting new parts into a worn gearbox will only delay the inevitable.

I’d be taking a long, hard look at the battery. When a battery is at the end of its useful life, it will often show a 12-volt charge with a simple volt-meter check. But, when you turn the key and place a big load on the battery, it goes weak at the knees and won’t turn the engine over.

Have the battery load tested. This will tell you more about what’s going on. The reason the car started with a jump-start form another car is that the second car’s battery has stepped up to do the job your car’s battery can’t.