An intake problem with the turbo-diesel engine in the top-selling Toyota HiLux ute — which was identified during a motoring.com.au comparison test, triggers ‘limp-home’ mode and turns off safety features including stability control — will be the subject of an urgent redesign in Japan.
But Toyota Australia cannot yet confirm if the solution will be offered as a retrofit for the 170,000-plus Toyota HiLux, Fortuner and Prado vehicles already on local roads with the 2.8-litre four-cylinder turbo-diesel engine.
And it is refuting suggestions this is a safety issue that requires a recall to fix, or that engine longevity could be affected.
“As the vehicle is subject to reduced engine power and can continue to be operated safely, it is not a safety related item that would require a recall,” a Toyota Australia spokesperson told motoring.com.au in a statement.
The design flaw allows dust to leak past the air-filter and corrupt the readings the mass air-flow sensor (MAF), which measures the rate of air entering the direct-injection engine. The engine control unit (ECU) uses the reading to determine the correct air/fuel ratio.
The corrupted data prompts the engine to go into limp-home mode — a potentially dangerous outcome in the wrong situation, such as when overtaking.
It also turns off the stability and traction control systems and, depending on the instrument panel fitted to the vehicle, instructs the driver to visit a Toyota dealer or consult the owner’s manual.
“The vehicle takes a conservative approach and disables the safety systems entirely instead of making an inaccurate judgment using incorrect or incomplete data,” the spokesperson explained.
The engine in our test HiLux Rugged X went into limp-home mode four times without any warning. It was temporarily fixed each time by disconnecting and reconnecting the battery.
But motoring.com.au is also aware of a Fortuner press vehicle having the same problem. That vehicle went into limp-home when the driver was attempting to pass a B-double on an outback road.
The problem is a major embarrassment for Toyota, which prides itself on its reputation for quality and reliability and markets the HiLux as ‘unbreakable’.
In essence, three vehicles promoted for their off-road use have a design fault that affects their capability to perform in that environment.
The HiLux has been Australia’s top-selling vehicle for the last two years and the Prado has been the nation’s most popular large SUV for longer.
The downsized 1GD-FTV turbo-diesel in question made its Australian debut in the Prado in August 2015, shortly before appearing in the current HiLux and Fortuner in October 2015.
More than 170,000 vehicles fitted with this engine are now on Australian roads.
“The dust that makes its way through the filter is very fine and typically less than five microns in size. What can occur is that these very fine particles attach themselves to the sensor electrostatically,” the Toyota spokesperson said.
“It is not an issue of the dust finding their way into any internal components of the MAF sensor.”
While Toyota Australia is only publicly acknowledging the issue in the wake of our test, it issued service bulletins to dealers as far back as March 2017.
At that stage it advised dealers that the HiLux, Fortuner and Prado required air-filter cleaning more often when they are used in dusty conditions.
The bulletin also recommends an additional two-minute procedure to blow compressed air past the MAF sensor.
Owners are also being made aware of the issue and being advised to clean the air-filter more often.
“It’s important that the air-filter is checked more regularly in extremely dusty conditions … it’s an easy fix to have dust blown out [to clean the sensor].”
It has also been found that an air snorkel, such as the one fitted to the Rugged X we tested, can exacerbate the problem in dusty conditions.
Toyota says that issue can be reduced by turning the intake rearward, a recommendation it makes in the owner’s manual.
But the real fix is a redesign of the air inlet system and that is happening in Japan.
“We have provided details of the experiences in the field in Australia to our head office in Japan and they will be making design changes to improve the performance of the air intake in extremely dusty conditions at the earliest possible opportunity,” the spokesman confirmed.
The redesigned air intake’s introduction timing is unknown.
“Any change to the intake system will affect emissions and homologation and therefore will require extensive retesting,” said Toyota.
“At this stage we believe it will not make it in time for the next technical change but we will endeavor to expedite this so it is implemented at the earliest production opportunity.
“We have requested that any changes to the air intake or other related systems be made available also to vehicles already in the field.
“However, as the design is not yet complete, it is too early to say whether this will be possible.”
Toyota will retrofit parts free of charge, the spokesman said, but is playing down the extent of the limp-home issue, saying it strikes only rarely and only in “extremely dusty” conditions.
It also downplayed the prospect of engine damage from dust ingress.
“The dust particle size that passes through the air intake system can become statically charged and adhere to the MAF sensor,” said Toyota.
“The size of these particles is around two microns. In general this type of very fine dust is not known to cause engine damage.”