NUT 2526241 - Caterpillar

The control is capable of self-diagnostics for the sensors, for the signals from the sensors, and for the motor for the fuel valve.If an alarm condition is detected, the "ALARM" indicator on the control will illuminate. The output switch for the alarm will be activated. "!" will follow the "MAN" mode or the "Auto" mode if the home status screen is active on the display screen. An "ALARM" message with a brief description of the condition will flash on the lower line of the display. The display screen will continue to display the active "ALARM" message when a diagnostic fault is present. The active "ALARM" messages are rotated to the bottom line of the home screen.If all the diagnostic 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 and full access to the functions of the keypad will be re-enabled.There are 12 different specific diagnostic conditions which may be reported."ALARM LEAN LIMIT" (Maximum)
Illustration 1 g01389913The "ALARM LEAN LIMIT" message indicates that the position of the fuel valve has reached the maximum limit of 1700 steps. The control has determined that the air/fuel mixture is too rich but the control cannot lean the mixture because the fuel valve is at the leanest limit.Possible Causes
The NOX sensor is not operating or calibrated.
The fuel pressure to the engine is too high.
The load control valve is allowing too much fuel to enter the inlet manifold.
The setpoint for the NOX target is beyond the capability of the engine's operation.
The harness for the fuel valve's motor is disconnected.
The fuel valve's motor is damaged.
The circuit driver for the fuel valve's motor is damaged.
There is some other problem with the fuel system."ALARM RICH LIMIT" (Minimum)
Illustration 2 g01410681The "ALARM RICH LIMIT" message indicates that the position of the fuel valve has reached the minimum limit of 0 steps. The control has determined that the air/fuel mixture is too lean but the control cannot richen the mixture because the fuel valve is at the richest limit.Possible Causes
The NOX sensor is not operating or calibrated.
The fuel pressure to the engine is too low.
The load control valve is not allowing enough fuel to enter the inlet manifold.
The setpoint for the NOX target is beyond the capability of the engine's operation.
The harness for the fuel valve's motor is disconnected.
The fuel valve's motor is damaged.
The circuit driver for the fuel valve's motor is damaged.
There is some other problem with the fuel system."ALARM IMAP PWMhi"
Illustration 3 g01389930The "ALARM IMAP PWMhi" 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."ALARM IMAP PWMlo"
Illustration 4 g01389934The "ALARM IMAP PWMlo" message indicates that the duty cycle of the manifold air pressure sensor is less than five percent.Possible Causes
The sensor is