The Dosing Control Unit (DCU) communicates any
error conditions from temperature sensors that are
connected to the DCU to the engine ECM over the
CAN C data link.
Note: The following conditions must exist before any
of the above codes will become active:
• The ECM has been powered for at least 2
seconds.
• There are no active 168-X diagnostic codes.
The ECM will log the diagnostic code. If equipped,
the warning light will come on.
This procedure covers open circuit diagnostic codes
and short circuit diagnostic codes that are associated
with the following sensors that are connected to the
DCU:
• DOC inlet temperature sensor
• DPF inlet temperature sensor (if equipped)
• SCR inlet temperature sensor
This procedure covers open circuit diagnostic codes
and short circuit diagnostic codes that are associated
with the following sensors that are connected to the
ECM:
• Coolant temperature sensor
• Intake manifold air temperature sensor
• Fuel temperature sensor
• Air inlet temperature sensor
• ATAAC outlet temperature sensor
• NRS inlet temperature sensor
• Aftertreatment ambient air temperature sensor (if
equipped)
The following background information is related
to this procedure:
The troubleshooting procedures for the diagnostic
codes of each temperature sensor are identical. The
temperature sensors have two terminals. The signal
line is connected to each sensor connector terminal
1. Terminal 2 is the return line. The signal voltage
from terminal 1 of each sensor is supplied to the
appropriate terminal in the ECM or the DCU.
Pull-up Voltage
The ECM and the DCU continuously output a pull-up
voltage on the circuit for the sensor signal wire. The
ECM/DCU uses this pull-up voltage in order to detect
an open in the signal circuit. When the ECM/DCU
detects a voltage above a threshold on a signal
circuit, an open circuit diagnostic code (XXX-3) is
communicated to the engine ECM.
If the sensor is disconnected, pull-up voltage at the
connector indicates that the wires are not open or
shorted to ground. If the sensor is disconnected, the
absence of pull-up voltage indicates an open in the
signal wire or a short to ground. If the sensor is
disconnected and the voltage is different from pull-up
voltage, the signal wire is shorted to another wire in
the harness.
394 UENR4469-36
Circuit Tests
Copyright of Perkins Engine Company Limited. NOT FOR REPRINTING OR RESALE
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