In 1983 Oaf was among the first manufacturers to offer
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a vehicle diagnostic unit. It was expensive with a limited range of functions, but as electronics have advanced so has Oaf's Davie tester. We've been to see what the latest XD version is capable of.
Mrith the advance of sophisticated vehicle electronics, most manufacturers have naturally developed their own diagnostic equipment. Systems range from complex assemblies that would be vulnerable to damage in a busy workshop environment to rugged devices for roadside use.
The arrival of Dafs CF and LF models with their CAN-bus (controlled area network) "electronic highway" has coincided with the appearance of the third-generation Davie XD diagnostic unit. This electronic tester with its twin integrated oscilloscopes is tailored to suit the latest models; and Dafs customer services manager, Bill McIntyre, has taken time out to
show CM what it's capable of. In older Dafs electronic systems like DIP (digital instrument panel), ECAS (electronically controlled air suspension), ABS and EBS (electronic braking system) were stand-alone items. But thanks to the CAN-bus systems they now communicate with each other.
Life has also been made easier in the workshop. With previous models of the Davie tester the mechanic had to find out which electronic systems were fitted to a particular truck and input the details before attempting to fault find.
But in its latest incarnation the Davie XD stores so much electronic data that the mechanic simply feeds in the chassis number and all is revealed. Updates can be handled via the Internet or a disc (much like Daf s Rapido parts system).
Internet communications are two-way, of course, and the dealers' computers are linked to Daf so Eindhoven can monitor service operations and fault frequencies via dealer and Davie ID codes.
There are two diagnostic paths to choose from, depending on the mechanic's skill and experience. The direct route is designed for isolating specific problems; the guided diagnosis system follows a step-by-step path through various checks to the source of the defect.
Older Davie testers relied on a 'tree-like' fault finding process, running down the trunk and through a series of branch-by-branch checks to find the problem. The XD uses a "spider's web' system the technician can begin in 'direct' mode and can switch at any stage to or from the "guided' path. The test results are stored for continued fault finding. Two levels of access are provided, for mechanics arid for administration.
Digital instruments, ECAS, ABS and electronic engine management aren't new to Daf, but EBS is. With disc brakes all round there's much less actuator travel and less air displacement too, so reaction times are shorter.
For brake shoes to even touch on a drumbraked rig can take 0.2-0.3 bar; some trailers with their anti-predominance valves and pulloffsprings need t.o bar down the yellow (service) line, With Daf's CAN-bus system, brake pedal pressure instantly puts out a threshold value to all the chambers and primes the air system; this also cuts response times.
The new Davie XD comes with a basic station and radio-linked interface; a printer is optional.
Fault finding
So when it comes to fault finding the Davie XD is already programmed with wheel size, differential and gear ratio details. Better still, there's no longer any need for load sensing as all systems are linked via the CAN-bus network. So just as the engine ECU knows how much fuel, torque etc is needed to move a laden truck, the brake ECU knows the weight from the CAN-bus network data and can work out how much effort is needed to stop it.
If things go awry electronically, there's always the conventional pedal-operated dual air braking system to fall back on. "Daf's truck range has really advanced," says McIntyre, "but so too has Davie diagnostics," U by Bryan Jarvis