PLATE 8W8456 - Caterpillar

The control is capable of self-diagnostics for the sensors, the signals from the sensors, and the motor for the fuel valve.If an alarm condition is detected, the "ALARM" indicator on the control will illuminate continuously. The output switch for the alarm will be activated. If one of the status screens is on the display, a "" screen with a brief description of the condition will flash on the screen. The display will continue to flash while the condition is present.If the condition becomes inactive, the "ALARM" indicator and the "" screen will be deactivated.
"ALARM ACK" key - Press this key in order to acknowledge an alarm. This will deactivate the output switch for the alarm. The "ALARM" indicator will flash. "Map Signal Lo"
Illustration 1 g00784229
The "MAP SIGNAL LO" message indicates that the duty cycle of the manifold air pressure sensor is less than five percent.Possible Causes
The sensor is not connected.
The supply wire has an open circuit or the wire is shorted to ground. Check for 24 volts at the connector for the sensor.
The signal wire has an open circuit or the signal wire has a short to the common circuit.
There is a problem with the sensor."Map Signal Hi"
Illustration 2 g00784239
The "MAP SIGNAL HI" message indicates that the duty cycle of the manifold air pressure sensor is greater than 95 percent.Possible Causes
The sensor's return wire has an open circuit.
The signal wire has a short circuit to positive voltage.
There is a problem with the sensor."No Buffer Load"
The control has an output switch that provides power to the oxygen buffer. The buffer is powered down when the engine is not running. This helps conserve the service life of the oxygen sensor.
Illustration 3 g00784244
The "NO BUFFER LOAD" message indicates that an engine load is detected when the buffer is OFF.Possible Causes
The buffer is disconnected from the control.
There is an open circuit in the supply wire or the return wire.
There is a problem with the buffer."O2 Sensor Fault"
Illustration 4 g00784248
The "O2 SENSOR FAULT" message indicates that the duty cycle of the oxygen buffer is between 10 and 20 percent.Possible Causes
The sensor is disconnected from the buffer.
There is a problem with the sensor.
There is a problem with the buffer."O2 PWM Signal Low"
Illustration 5 g00784251
The "O2 PWM SIG LO" message indicates that the duty cycle of the oxygen buffer is less than ten percent.Possible Causes
The buffer is disconnected from the control.
The supply wire for the buffer has an open circuit or the wire is shorted to the return wire.
The signal wire from the buffer is shorted to the return wire.
There is a problem with the buffer or the oxygen sensor."O2 PWM Signal Hi"
Illustration 6 g00784255
The "O2 PWM SIG HI" message indicates that the duty cycle of the oxygen buffer is greater than 95 percent.Possible Causes
The buffer's return wire has an open circuit.
The signal wire from the buffer is shorted to positive voltage.
There is a problem with the buffer or the oxygen sensor."O2 Cal Fault Lo"
Illustration 7 g00784269
The "O2 CAL FAULT LO" message indicates that the control has determined that the percent of