© MAHLE
6 | OBD-II Smartbox | Product Use
en
3.1.2 Test with ignition key in ON position
If the first test did not indicate any problem, then proceed with
the second test. With the OBD-II Smartbox still attached to the
vehicle DLC, switch the ignition key to ON position then press
Retest button on the OBD-II Smartbox once.
The test starts immediately with the testing of all the 14 pins other
than pin 4 chassis ground and pin 16 positive Voltage supply. At
the same time it will detect the type of communication protocol
(PWM, VPW, ISO 9141-2, ISO 14230-4, CAN H, and CAN L)
that the ECU is using and the blue LEDs will blink indicating the
protocol currently being used.
If any voltage present on vehicle Manufacturer designated pins No.1,
3, 8, 11, 12 & 13 (yellow color socket) other than OBD2 assigned
protocol pins 2, 6, 7, 10, 14, 15 (blue color socket) and 5 (Signal
ground), the corresponding LED will light in the following manners:
y
If there is 12V present– the LED will blink slowly at interval of 1 sec
between each blink. (The ‘Caution – Check LED will illuminate).
y
If there is 24V present – the LED will blink fast. (The ‘Caution
– Check LED will illuminate).
In situation where there is 12V or 24V present at the pin, the
voltage was either supplied direct short or through a resistor. Its
resistance value is normally not more than 20Ώ.
However, when a voltage 0V is supplied from the other end of the
Scan tool to this pin, a current bigger than 0.6A will flow. This indi-
cation serves as a warning when using Scan tool without current
limiter built-in because this voltage may damage it when plugged in.
In many cases, Vehicle Manufacturers do provide some pins on
the OBD-II Diagnostic Link Connector (DLC) at the vehicle for
RPM signals or Sensors signals used for testing or adjustment.
These signals are usually found on any of the Manufacturer des-
ignated pins No.1, 3, 8, 11, 12 &13 on the DLC. Therefore such
signals will be detected and indicated as “Caution – Check”.
In other words, you can still plug in and use your scan tool but
with risk in case where the Scan tool has no protection.
It is also important to note that the presence of voltage in one of
the pins maybe one of the reasons why sometimes communica-
tion failed between Scan tool and ECU because of the presence
of the 12V or 24V shorting.
However, almost all Scan tools nowadays come with protective
current circuit and this indication should not be accepted as
danger but served as a warning.
