Professional_Tool_And_Equipment_News_September_2020 - 30

Whether you're diagnosing the
cause of the fault code or the cause
of a converter failure, your scan tool
will be necessary, but you'll also need
additional tools. Your scan tool will be
required to monitor the datastream of
the O2 sensors, engine temperature, fuel
trim, and other factors the PCM uses to
maintain control of the fuel the engine
is using. Keep in mind, the primary
goal of an OBD-II system is to monitor
and control the engine fuel system to
reduce emissions and maintain catalytic converter functionality, and then
alert if there are any catalyst damaging
events occurring.
Because exhaust leaks may allow air
to enter the exhaust stream between
the upstream and downstream O2 sensors, it's a fairly common reason a faulty

converter code will set, even if the converter is functioning correctly. The best
tool I have found to check for exhaust
leaks is a high- pressure diagnostic smoke
tester. The higher pressure this tool creates, rather than a traditional smoke
machine, will allow you to detect even
the smallest leaks in an exhaust system.
Another easily overlooked cause of
catalytic converter failures is a system
that runs overall lean or rich. To check
this part of the system, you'll need a
fuel pressure gauge, preferably one that
allows you to check volume as well as
pressure, along with your scan tool,
which will enable you to command a
PCM controlled fuel pump at full speed.
Other tools I've found to be useful
when checking the fuel pump are a
digital multimeter (DMM) or a Fuse

Buddy. Both tools allow you to easily
measure the current that the fuel pump
is drawing to deliver fuel. A general rule
of thumb is that a properly functioning
fuel pump will draw 1A for every 10
psi of fuel pressure. For example, a 70
psi system should draw approximately
7A. Higher current draw can indicate a
faulty pump, or a restriction in the system (filter). A lower than normal draw
may be an indicator of a fuel pump that
is cavitating, or high resistance in the
electrical supply to the fuel pump.
These are just a few examples of
additional tools that are required to
fully test a system after using your scan
tool to do a preliminary check. In an
upcoming article, we'll discuss the benefits of including a lab scope in your
diagnostic toolbox.

RELATED TOOLS
Ranger
AC-134 CoolCharge

Circle 76 on card, or enter
at "e-inquiry" on
VehicleServicePros.com

Proflex+
Pro S-600T TURBO
Smoke Monster

Lisle Corporation
CAT III Digital Multimeter,
No. 82600

Circle 75 on card, or
enter at "e-inquiry" on
VehicleServicePros.com

Circle 77 on card,
or enter at "e-inquiry" on
VehicleServicePros.com

Redline Detection
Dual Purpose Diagnostic
Leak Locator, No. 95-013
Circle 78 on card, or
enter at "e-inquiry" on
VehicleServicePros.com

30

PTEN

SEPTEMBER 2020

www.VehicleServicePros.com

Ritchie Engineering Co.
Yellow Jacket ManTooth
Wireless Digital Gauge Kit
Circle 79 on card, or
enter at "e-inquiry" on
VehicleServicePros.com

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Professional_Tool_And_Equipment_News_September_2020

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