TM 5-3805-293-23-1
0011
Table 2. Engine Troubleshooting with Codes for the 120M Motor Grader - Continued.
CDI FMI CODE
ERROR/EVENT
CORRECTIVE ACTION
N OT E
0342-08 Secondary Engine
Speed Sensor Abnormal
The engine uses two engine speedsensors. The engine speed sensor
Frequency, Pulse Width, or
is located on the left hand side of the cylinder block close to the flywheel
Period - Continued
housing. The secondary engine speed sensor is part of the fuel injection
pump. The engine speed sensor, which is mounted on the cylinder
block, generates a signal by detecting the movement of the teeth that
are located on the speed/timing wheel. The speed/timing wheel is
connected to the crankshaft. The Engine ECM uses the speed sensor
signal to calculate the position of the crankshaft. The signal is also used
to determine the engine speed.
The 8-Volt supply circuit is a common supply circuit which is bussed
internally of the Engine ECM. Output of the 8-Volt supply circuit is at
Engine ECM J1-43 and J2-10. The 8-Volt supply circuit 996-GN is
spliced externally of the Engine ECM from J2-10 and is supplied to the
engine speed sensor and the secondary engine speed sensor (on the
fuel injection pump). The 8-Volt supply circuit J844-GY is also supplied
to the throttle position sensor from the Engine ECM from J1-43.
The secondary engine speed sensor is located in the fuel injection
pump. The secondary engine speed sensor generates a signal that is
related to the camshaft position. The fuel injection pump is
mechanically connected to the camshaft. The secondary engine speed
sensor detects the movement of the teeth on the speed/timing wheel in
the fuel injection pump. The ECM calculates the speed and the
rotational position of the engine by using the signal. The secondary
engine speed sensor is required for starting purposes.
During normal operation, the secondary engine speed sensor is used to
determine the cycle that the engine is on. When the timing has been
established, the primary engine sensor is then used to determine the
engine speed and the angular position.
The loss of signal to the engine speed sensor and/or the secondary
engine speed sensor will result in one of the following faults:
-
The loss of signal from the secondary engine speed sensor during
start-up will prevent the engine from starting.
-
The engine will continue to run when only one sensor signal is
present from either the engine speed sensor or the secondary
engine speed sensor.
-
The loss of signal from the primary speed/timing sensor during
operation of the engine will result in engine operation with a derate.
-
Loss of signal from the engine speed sensor and the secondary
engine speed sensor during operation of the engine will cause fuel
injection to be terminated and the engine will stop.
-
The engine speed sensor and the secondary engine speed sensor
are interchangeable components. The sensors may be exchanged
in order to eliminate a fault. If a secondary engine sensor is suspect
and a replacement secondary engine speed sensor is not available,
then the engine speed sensor and the secondary engine speed
sensor can be exchanged. This will allow testing to determine if the
secondary sensor is faulty.
Change 1
0011-120
