There is a Mack Granite on the hard shoulder of the A6 near Barton-le-Clay, and the driver has been sitting on the barrier for forty minutes.
The ABS light came on somewhere outside Milton Keynes. He kept going because he had a delivery and because the brakes felt fine to him. That is the part that worries me most – not that he ignored it, but that he was completely right about the brakes feeling fine.
Mack and Volvo have announced a recall covering approximately 5,100 commercial trucks for an ABS fault that passed through production without being identified. The specific issue is electrical – a flaw in the wiring or connection that feeds the ABS controller. Under the right conditions, the system can lose its ability to accurately monitor wheel speed, which is the only thing ABS is actually doing.
The thing about electrical faults in commercial vehicle ABS systems is that they rarely announce themselves cleanly. I have connected my kit to trucks where the fault code said wheel speed sensor and the live data showed the sensor working absolutely fine. That contradiction is where the actual diagnosis starts, not where it ends.
On this particular job, the code was pointing at the rear axle modulator. I went to the ABS control unit connector first – not where the code was pointing, not even close. It had exactly the corrosion you see on any vehicle doing regular motorway miles through salt and standing water. The code was the system's best guess at the symptom, and it was not wrong, but it was not pointing at the cause.
Production electrical faults have their own character. A connector that seats perfectly in a dry factory at controlled temperature behaves differently after eighteen months of vibration, heat cycling, and British road grime. That is not negligence on the production line – it is the gap between a quality check and a working environment.
The concern with a recall of this scale is what happens to the trucks that do not go back in time. Commercial operators are under pressure in a way that private owners are not. A fleet manager who sees an amber ABS warning is weighing up downtime, delivery schedules, and whether the vehicle technically stops when tested. The answer to that last question will usually be yes – which is exactly why these faults get deferred.
On trucks in this category, the components that get blamed first are almost never the ones at fault. The ABS modulators and sensors in commercial systems of this type are built to last. The failure mode is almost never the sensor or the modulator itself. It is the electrical path between them – the connector, the ground, the harness routing.
Replacing the modulator without first confirming the electrical path is clean and seated correctly is the kind of decision that generates a return call six weeks later. I documented a similar fault on a Volvo FH last spring. The comment section filled with fleet mechanics from across the country saying they had seen the exact same failure pattern on the same model. That kind of response tells you more about how widespread a fault genuinely is than any recall announcement does.
The other thing worth saying is that this recall covers trucks that are still actively working. These are not vehicles sitting in a yard waiting for attention. ABS on a loaded commercial vehicle is not the same as ABS on a family hatchback.
The stopping forces involved, the axle weights, the braking distances – the system is working significantly harder than most people realise. An electrical fault that produces an intermittent hesitation on a car can produce a full non-activation on a truck under load.
If your vehicle is in the affected range, get it booked now. Do not wait for the brakes to behave differently, because with a fault like this, they probably will not give you any advance warning.
Five thousand trucks is not a small number. The flaw did not make it past production through carelessness – it made it past because it only reveals itself under conditions a factory check cannot replicate. That is exactly the kind of fault I find on driveways and hard shoulders every week, on vehicles nobody has recalled. What I keep thinking about, closing the van doors on the way to the next job, is everything that looks identical to this and has not been found yet.
Jimmy O’Riley is a UK-based mobile mechanic and automotive diagnostic specialist operating out of Bedfordshire, England. He founded O’Rileys Autos in 2011 with a focus on bringing professional vehicle repairs directly to customers at their homes and workplaces.
With over a decade of hands-on experience, Jimmy specializes in ABS diagnostics, brake system repairs, diesel emissions faults, and DPF cleaning. He is recognized across the UK and Ireland as one of the leading specialists in vehicle braking and emissions systems, earning the title “The DPF King” from his growing online audience.
Jimmy documents real-world automotive repairs through his YouTube channel, which has accumulated over 97,000 subscribers and nearly 2,000 published repair videos. His content covers ABS fault diagnosis, wheel speed sensor testing, brake module replacement, and roadside repair procedures across a wide range of vehicle makes and models.
He is active on YouTube, Instagram, and Facebook under O’Rileys Autos.