Early diagnosis 28 August 2014

Troubleshooting electrical and electronic problems on commercial vehicles requires a structured, but also a computer-assisted approach. Toby Clark looks at the role of diagnostics

As commercial vehicles have become more sophisticated, managing electrical and electronic systems has moved away from diagnosing and repairing discrete units – starter motors, lighting, cab equipment and little else. Now, the technologies are integral to almost every component, whether it be the engine management system, or cooling, braking, steering or suspension system. The ubiquitous CANbus also ties all these together, so it is almost impossible to make a mechanical change without a corresponding electrical or electronic one.

As a result, the emphasis has largely moved away from specialist vehicle electricians. Now, almost every technician needs some ability to diagnose and repair electrical and electronic subsystems. As Phil Whitehead, training manager at fleet maintenance specialist Pullman Fleet Services, put it: "Probably eight out of 10 of our technicians, have multimeters in their tool boxes." And Jim McGuckin, dealer principal at Imperial Commercials in Bellshill and Cumbernauld, says many of his technicians also use multimeters and PicoCcopes (laptop-driven oscilloscopes) to measure signals.

But it's not just about the kit. McGuckin believes technicians need to start from first principles and not discount anything. "I say, please go and check the basics first. I'm very passionate about that," he advises, insisting that they shouldn't simply jump on with the diagnostic kit. "For example, if a vehicle doesn't start, they should check that there is fuel in the tank. And if all the systems are dead, they should check that the batteries are still there. We have had them stolen overnight."

McGuckin also points out that, before a technician gets his or her hands on a vehicle, it is vitally important to establish the precise symptoms. "We need service advisors to ask pertinent questions," he suggests. "A five-minute stint of test driving can be very useful. As can bringing in a master technician to discuss the problem directly with the driver."

Pullman's Whitehead worries that while most problems are communicated through written defect notes, "in a breakdown situation we tend to get it verbally from the driver". That can be a problem, particularly if a driver doesn't want to admit he's broken something, and just says 'It's stopped working'.

McGuckin cites one case of a tachograph problem that could not be replicated in the workshop. Only when the driver was quizzed and explained that 'it only does it going round a left-hand corner' was it diagnosed as a wiring loom problem. "It would look like somebody had disconnected the plug, and that would mean trouble."

Says Whitehead: "Generally electrics – lights and wiring – are the most common problem areas." And while agreeing that, often, they are not expensive to rectify, he adds that sometimes a problem has been caused or compounded by a previous fix. "Things will just expire. It's random, but it comes down to the quality of the repairs. They can just break down."

But while common causes of problems include overheating and mechanical wear, another that comes up as most troublesome is water ingress causing corrosion. McGuckin points to EBS (electronic braking system) sensors, particularly those in exposed positions on trailers. Similarly, the sensors for SCR (selective catalytic reduction) and EGR (exhaust gas recirculation) systems are exposed and can cause problems, though these tend to show up on the dashboard warning lights.

Waterproof grease or Vaseline should be used whenever connectors or diagnostic sockets are exposed, advises McGuckin. "Your wiring looms now are so fine, and the CANbus relies on such tiny impulses, that any [corrosion] may show up as a fault."

With modern Euro 5 and Euro 6 engined vehicles, general sensor faults are also possible. Dashboard error lights and fault code readers might identify the faulty component, but not necessarily the nature of the fault. This, says Whitehead, is where diagnostic systems score. "Nine times out of 10, the man with a garage down the road won't be able to do anything without this equipment."

But while diagnostics systems have been an essential part of any workshop's armoury for several years, they're even more important today. Third party diagnostics manufacturer Eclipse Automotive Technology points out that a Euro 6 engine can produce over 3,500 fault codes, with other truck and trailer systems adding many more. So, plainly, technicians need help in interpreting and responding to this volume of data.

Systems such as Eclipse's Jaltest, Actia's Multi-Diag and Texa's Axone 4 can search multiple truck makers' systems and give explicit descriptions of errors. Most work with libraries of known faults to allow symptom-driven diagnosis and step-by-step rectification. Importantly, they're also intuitive, meaning that technicians can work more efficiently, quickly getting to an analysis of the problem, and making repair faster, easier, cheaper – and better.

And with modern trucks, it's not just about problem resolution: sophisticated equipment is needed at the repair stage too. As Whitehead says, "When you fit something, you can't just bolt it on. You have to recalibrate or program it." That's certainly the case when replacing a VGT (variable-geometry turbocharger) or an airflow meter. "We've invested a lot of money in this technology because it's required," he insists. "Our customers need us to have that ability – and hopefully to deliver a first-time fix, too."
That said, although modern diagnostics systems offer a step-by-step approach, technicians still need training to get the most out of them. All reputable suppliers offer it: Eclipse, for example, runs courses on-site or at its facility in Swadlincote, Derbyshire, which sports several test beds set up to simulate faults. But the trick is making it affordable. One way is to send super-users or master technicians on the courses, leaving them to train their colleagues.

Whitehead reckons that, as a result, Pullman can take a new technician and get him or her from zero to intermediate level in a day or two. "We've got some guys that have never picked up a computer in their life but they use our system to diagnose and calibrate vehicles on a weekly basis." He also says that super-users can feed information back to diagnostics providers. "The partnership between us and Eclipse is very important," says Whitehead. "The feedback helps Eclipse to develop the product and Pullman to improve work processes."

McGuckin runs a DAF and Fiat workshop, but makes the point that the dealership needs to look after customers' other vehicles, too. "We invested recently in all-makes diagnostics equipment," he says – coincidentally also Eclipse's Jaltest. His only observation: when you're looking at all-makes it's generalised training, it cannot be in-depth. That's why Imperial Commercials doesn't rely solely on its diagnostics systems for data. It also subscribes to the E3 Technical service, which gives detailed specification and repair information for specific vehicles, identified via a registration mark lookup.

Whatever you do, everyone agrees you need to keep up to date. As McGuckin says: "Your technicians need to embrace technology, or it will run away from you." And remember the value of telephone support: two heads are better than one, and a three-way conversation between the driver, a technician and the diagnostics call centre can be even better.

Toby Clark

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Related Companies
Actia (UK) Ltd
DAF Trucks Ltd
Eclipse Automotive Technology Ltd
Imperial Commercials Ltd
Pullman Fleet Services
Texa UK Ltd

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