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.

If we’re talking about the current model D-Max and BT-50, then yes, the entire driveline should be interchangeable. Under the skin, both the Mazda and Isuzu utes are the same vehicle. Car makers enter into joint ventures like the development of this pair of vehicles to keep costs down by sharing the expense of developing, engineering and testing parts like engines, transmissions and, of course, drive-shafts and CV joints.

While most joint ventures like this one will arrive at two vehicles with some visual differences and usually some details differences inside, when it comes to the oily bits, making specific driveline or suspension parts for one vehicle over the other is defeating the purpose of the joint venture in the first place.

It sounds awfully like the car has entered what’s called limp-home mode. As the name suggests, this allows the ute to run just enough to get you to a workshop without damaging anything else. Limp-home is usually associated with a problem in one of the car’s systems, whether that’s electronic, fuel-system, exhaust system (DPF) or a mechanical fault with the engine or transmission. It’s kind of a self-preservation function.

The good news is that you’re still well and truly overed by the factory warranty, so it’s back to the dealership for your BT-50. This is absolutely Mazda’s problem, not yours.