Isuzu D-Max Problems

It sounds very much like the vehicle has gone into limp-home mode. This is a self-preservation system whereby the engine and drastically reduces the power it’s producing, limits top speed and often locks the transmission into a low gear. Something has happened that has caused this, and a common reason is that something in the engine, fuel system, or (more likely) the transmission has started to get too hot with the strain of towing.

With luck, full operation will be restored once the vehicle has been allowed to cool down. But you may need to visit a dealership to have things reset. It’s always a good idea to do a full engine and transmission fluid and filter change after any overheating event anyway.

The list of possible causes for a modern turbo-diesel engine not to start would fill a pretty large book, and there’s no point trying to guess the problem. If the engine is cranking but nothing else is happening, most mechanics will start by looking at the fuel system. There could be a problem with the tank pick-up, the fuel rail, the injectors, the filters and many more components. But a check of the fuel delivery pressure and volume is a good place to start.

But this is not a job for the amateur in their driveway. Modern diesels use super high injector pressures, and, if there’s any residual pressure in the system when you crack it open, that pressure is enough to remove fingers, just like a high-pressure water jet can cut steel.

Cars are often less than perfect and problems can show up once they are released on to a particular market with particular conditions. But every new make and model that hits the road and is eligible for registration has to pass a range of tests and certifications before the government will allow that to happen. So your question is really one for government, but the reality is that in many cases, nobody can see these problems coming.

Meanwhile, while I won’t speak for every `information’ source on the internet, I can say without fear of contradiction that no road tester or writer for Carsguide accepts payments from car importers for their opinion. Social media influencers may be a different matter, but I promise you that anything published on Carsguide is the truth and in no way influenced by the car maker or importer. We now live in an age where you need to be very careful where you source your information, but Cargsuide is one source you can trust. It’s something the writers (my colleagues) are very proud of.

Let’s start at the start. The SVS light on your car stands for 'Service Vehicle Soon'. Fundamentally, it’s telling you that something is not right somewhere on the vehicle and the computer has logged the fault. That’s why a scan showed up the code PO661.

On this vehicle, code PO661 relates to the electronics that control the swirl valve inside the intake manifold. This valve works to create the maximum gas velocity inside the intake runners and, therefore, gain the cleanest, most complete burn of the fuel and air entering the engine. If this valve is not operating properly, you may find a loss of power as the turbocharger won’t be working at its most efficient. In some cases, the same fault code can show up because of a problem with the engine’s EGR valve which is also part of the engine’s intake system. This may require the manifold to be removed and manually cleaned.

However, it’s unlikely to be anything to do with the car’s air-conditioning system, which is more likely to be a coincidence. That said, if the engine is running hotter than normal because the intake system is not working properly, then the car may have an interlock that prevents the air-con coming on to help keep coolant temperatures at bay.

It’s not a problem we’ve heard of occurring in huge numbers, but like any component, a canopy is subject to wear and tear just like any other. Canopies on tradie-trucks can cop an awful hammering at the hands of their owners and damage is inevitable in such cases. Even a few years exposure to Australian levels of UV radiation can cause a canopy to start to break down structurally, so they generally have a finite lifespan.

But instead of replacing the whole canopy (assuming it’s a fibreglass one) it might be worth asking a fibreglass specialist (say, a boat repairer) if the crack can be repaired. That would certainly be cheaper than replacing the whole canopy

This really does sound a bit like a head gasket problem. Even though the coolant and oil aren’t mixing (as you might expect with a blown head gasket) if the gasket blows between the coolant passages and the combustion chamber, the pressure of the engine’s combustion (particularly when the turbocharger is boosting when, say, climbing a long hill) can pressurise the cooling system, leading to the sorts of problems you’re having, including ejecting the coolant all over the place.

But until you’ve done a couple of simple checks, there’s no way of knowing whether there’s a blockage or other problem with the cooling system that is allowing the engine to become too hot. At that point, the coolant will also force its way out of the engine with a similar set of symptoms. A chemical check (called a TK test) will be able to identify whether combustion gasses are finding their way into the coolant, suggesting a head gasket failure., A good mechanic should also be able to tell if there’s a blockage in the coolant system or a problem with the coolant pump.

The last decade of dual-cab four-wheel-drive utes have emerged as the tow-vehicles of choice, and you see them everywhere filling roles exactly like the one you have planned. Popular models include the Ford Ranger you’ve nominated, Toyota HiLux, Mazda BT-50, VW Amarok, Mitsubishi Triton, Nissan Navara and Isuzu D-Max. But there are also cheaper alternatives including makes like the South-Korean made Ssangyong and various Chinese brands like LDV and Great Wall.

Just make sure you know exactly how much you need to tow before making a decision as some of the cheaper models don’t have the same outright towing capacity and even if they do, some of them don’t have the engine performance to make towing as easy as it should be. For parts availability, the Toyota would be king in really remote areas, but any of the major brands are pretty well covered in Australia.

Meantime, don’t rule out ute-based wagons such as the Ford Everest, Isuzu MU-X, Mitsubishi Pajero Sport and Toyota Fortuna. These offer better ride comfort when unladen thanks to more sophisticated rear suspensions and most have as much or almost as much towing capacity as their ute brethren.

The digital displays on modern cars are known to sometimes randomly fail for no apparent reason. Sometimes it’s the whole display that fritzes, other times just a smaller part of the display will disappear. Usually, replacing the LED module is the fix.

From memory, this model D-Max groups the fuel and temperature gauges, odometer and the gear position information into a small unit in the middle of the dash binnacle. Which means it might be a bit complicated re-connecting the temperature and fuel tank sensor units to the new module, as well as making sure the new odometer reads the correct mileage for the vehicle. An auto electrician should be able to handle it, though.

Technically, of course, any car without a working gear-position indicator is unroadworthy, so this needs to be fixed rather than ignored.

This is a tricky one because the D-Max’s SVS warning light seems to be a bit of an all-rounder. That is, it indicates a fault, but a non-specific one. Certainly not one that can be read by the majority of aftermarket scanning tools. Logic suggests there’s something within the driveline that is getting too hot for the computer’s liking, a theory backed up by the fact that it only triggers when you’re towing a big load and the car is working its hardest.

The solution seems to be to present the car at an Isuzu dealership as this may be the only workshop that will have the D-Max-specific scanning gear to determine the cause or even narrow it down.

For the record, the SVS stands for Service Vehicle Soon, but I’m afraid even that’s a fairly generic recommendation and doesn’t get you any closer to the cause. That said, when engine oil or transmission fluid gets beyond a certain temperature, the computer will often detect this and call for a change of fluids as a means of driveline protection. This could be what’s happening every time you tow.