(Table 195, contd)
Diagnostic Codes for the Motorized Valves
J1939
Code
PDL Code Code Description
(code descriptions may
vary)
Comments
2791-6 3405-6 EGR Valve Control : Current
Above Normal
The ECM detects the following conditions:
A high current condition in the output for the NRS valve (EGR valve) for 2
seconds
The ECM has been powered for at least 2 seconds.
If equipped, the warning lamp will come on. The ECM will log the diagnostic
code.
2791-7 E1121 (2) EGR Valve Control Not Re-
sponding to Command
The ECM detects the following conditions:
The signal from the NRS valve position sensor indicates that the valve is not
in the desired position.
This diagnostic code can be caused by a loss of the 5 VDC supply to the
NRS valve position sensor.
The ECM has been powered for at least 2 seconds.
If equipped, the warning lamp will come on. The ECM will log the diagnostic
code.
The following background information is related
to this procedure:
NRS valve (EGR valve)
The NRS valve (EGR valve) is used to control the
amount of exhaust gas which is recirculated into the
intake manifold.
The amount of exhaust gas that is required is
calculated by the software that is contained in the
ECM.
The NRS valve is controlled by a PWM signal from
the ECM.
Exhaust Back Pressure Regulator
The Exhaust Back Pressure Regulator (EBPR) is
used to promote regeneration of the Diesel
Particulate Filter (DPF) and provide thermal
management of the Selective Catalytic Reduction
(SCR) system.
When the soot level in the DPF is high, the ECM
commands the EBPR to close. As the EBPR closes,
the increased back pressure causes the engine to
increase fuel flow. The increased fuel flow raises the
exhaust gas temperature and therefore accelerates
the regeneration process in the DPF.
As the soot level in the DPF reduces, the ECM
commands the EBPR to open, reducing the exhaust
back pressure to a normal level.
The EBPR is also used on engines with no DPF to
control deposit management.
The position of the EBPR is calculated by the
software that is contained in the ECM. The EBPR is
controlled by a PWM signal from the ECM.
Air System Motor Valves Verification Test
The Air System Motor Valve Verification Test will
identify whether the EGR valve, and the EBPR are
working correctly. This test must be run when the
engine speed is zero and the battery voltage is within
an acceptable range. For a 12VDC system, the
service test must only be executed if the battery
voltage is between 9VDC and 16VDC. For a 24VDC
system, the battery voltage must be between 18VDC
and 32VDC. If the battery voltage is outside of these
ranges at any time, the test must be aborted. The test
will also be aborted if a position sensor diagnostic, a
motor short diagnostic, or a motor open circuit
diagnostic become active.
If at any point during the test the engine speed is not
zero, the test will abort. The test moves the valves to
various positions and then checks the position sensor
within each valve to confirm that the valve has
responded correctly. Each valve will be tested in turn,
starting with the EGR valve. If a test threshold is
exceeded or any related diagnostics become active,
the test will abort and generate an error identifier.
356 UENR4469-36
Circuit Tests
Copyright of Perkins Engine Company Limited. NOT FOR REPRINTING OR RESALE
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