February 2023 - 21

* SERVICE INFO (INCLUDING
SYSTEM DESCRIPTION +
OPERATION FOR THE ADDED
ACCESSORIES)
* DVOM
* CIRCUIT LOADING DEVICES
* FLASHLIGHT
* FUSED JUMPER WIRES
* OE CAPABLE SCAN TOOL/J2534
DEVICE (OR FACTORY SCAN
TOOL/ INTERFACE)
and adequate voltage/ground supply before
condemning. With the connector separated
from the ECU, the technician makes the
measurements with the DVOM. This is
exactly what Leonard did, and the outcome
of the test indicated no outside circuit fault
present. This led to replacing the RPSD
control unit, per flowchart instructions.
What this flow chart failed to address is
that available voltage or adequate ground
supply is not a valid test. If the test results
indicate insufficient supply, then, of course,
" bad " is bad. But an open-circuit test like
that is not an accurate stressor of the circuit
being tested. A test conducted in this matter
can only truly indicate the continuity of
the circuit. However, it cannot determine
the circuit's ability to support current flow.
It goes back to the old anecdote regarding
the resistance of a copper cable with 100
strands of wire composing it. If one were to
slice 99 strands of the cable, the resistance
of the cable would still measure the same
(as before the cable was tampered with).
However, if one were to use that same single-strand
cable to complete a starter motor
supply circuit, one would realize quickly
that the cable does not support the required
current to operate the starter motor. The
tech would likely discover how that cable
makes a handy fusible link as the insulation
vaporizes to smoke!
Unfortunately, Leonard realized the
hard way that the prescribed test lacked the
information he needed to make an accurate
diagnosis. He had missed something,
p The rear floor was removed to inspect the mating of the original and conversion-harness.
and it had just hit him like a ton of bricks.
He realized that the test he performed did
not test the system under normal operating
conditions. To accurately test the system's
voltage and ground supply integrity meant
to test it when the circuit is functioning. The
problem is-the circuit doesn't function!
THE LOADED VOLTAGE DROP TEST
This all relates to the principles described
by Ohm's Law. As current flow increases in
a circuit, so too does the voltage dropped
across a resistor. In other words, if there is
no current flow present, the voltage will not
drop across any resistor-either intended
loads or unwanted resistance-in a circuit.
To conduct this test means to have the circuit
energized or functioning.
This power sliding door system didn't
respond to any switched-input or command.
FIRST TO
MARKET
Clamp Probe Set
Cat. No. 21200
Originally designed to allow a lone technician to test for voltage
drop on top battery posts; its handsfree operation is a useful
diagnostic tool when a third hand is needed.
* Works with standard 4mm banana plugs
op on op b
y p
; i s hand
op
h standard 4mm banana plugs
ion s a u
ul
* Probe swivels and adjusts in height to test where you need it
* Works great for testing recessed connections
* Clamp tips for added grip
* Works with standard 4mm banana plugs
* Works great for testing recessed connections
* Clamp tips for added grip
* Available individually as the 21215 (black) and 21216 (red)
* Available individually as the 21215 (black) and 21216 (red)
* Clamp tips for added grip
ailable ndi idually as the 1215 (bl
) and 212 6 (
d)
* Probe swivels and adjusts in height to test where you need it
Circle 52 on card or click " PTEN e-inquiry " on VehicleServicePros.com
www.VehicleServicePros.com FEBRUARY 2023 PROFESSIONAL TOOL & EQUIPMENT NEWS 21
2302PTEN_S&G Tool Aid.indd 1
1/10/23 3:43 PM

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February 2023

Table of Contents for the Digital Edition of February 2023