february2022 - 40

Vehicle Network Solutions
#1 IN SECURE
DIAGNOSTICS
Protect your Uptime
TRUCKCONNECT
» Always perform a voltage and resistance
check prior to using a multimeter.
Photo: 86372935 | Andrey Popov | Dreamstime
capabilities done on the lamp driver board,
Sniegocki explained. " They're able to provide and
deal with the electronic noise that might occur
throughout these systems, " he said. " And they're
able to filter that and provide only the necessary
signals back to the diagnostics architecture on the
truck itself. "
This protocol includes not only power and ground
to the LED headlamp, but the CAN bus or LIN bus
protocols depending on the vehicle architecture.
Technicians will always want to make sure one tool
is nearby to diagnose headlight issues: a multimeter.
" The multimeter will tell you if you have your
voltages correct-not just that you have voltage, but
if you have the correct voltage, " Miller said. " When
technicians go through the troubleshooting steps
with the proprietary software of the manufacturer,
it's going to ask them what the voltage is, because
that means something. "
Coyle agreed: " Keep that multimeter in your back
pocket, because you're going to need it. "
The multimeter itself requires a quick check to
ensure it is working properly. Coyle advised to do " a
quick voltage and resistance test with your leads to
make sure your meters work. "
Coyle always trains his technicians to " go back to
the basics " and reminds them to always check if the
power side has voltage and ground side does not.
" You can cut diagnostics down very quickly with
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just a couple of quick tests, " said Coyle, who explained
how OEMs' software provides active and inactive
fault codes emanating from the headlamp module.
Other systems can become impacted by issues
with the headlamp electrical system. " The module
can shut that circuit off if there's a short causing the
circuit to be damaged, " Coyle said.
Coyle explained one time he ran into an issue
where all the lights, the horn, and steering wheel
switches on a Freightliner Cascadia were not working
because the clock spring caught fire, melted some
wires, and shorted the data link. Once he unplugged
the burnt component, everything began to work.
To further speed up lighting troubleshooting, Coyle
built his own specialized diagnostics cart.
" I bought a really cheap, really small flat-screen
TV and put it on one side and a laptop tray on the
other, " he explained. " That way I've got my computer
set up so I can have wiring diagrams up on one side
and fault codes and diagnostics on the other side. "
This helps Coyle better understand if a circuit is
out, where it gets power from, and helps him identify
if there are any common issues in other circuits.
He found that technicians often do not test wire
resistance under a load. For small wires, Coyle uses
the Electronic Specialties LOADpro tool.
" The LOADpro uses the truck-supplied power and
ground on the circuit to make a connection across the
multimeter leads, " he said. " This allows the circuit
to be in a loaded state, and you are able to monitor a
voltage drop on your multimeter without having to
back probe the circuit. This can make voltage tests a
lot easier, and you are less likely to damage the seals
to the wiring terminals. "
" Keep that
multimeter in
your back pocket,
because you're
going to need it. "
Lucas Coyle, master technician,
TA Truck Service
http://www.Truck-Connect.com http://www.FleetMaintenance.com/inquire
february2022

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