GUARD AS 6P1872 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit for the fuel control solenoid. Also, use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
17-5 Fuel Shutoff Valve : Current Below Normal     The Electronic Control Module (ECM) detects a low current in the circuit for the GSOV for 5 seconds.
The output driver must be off for 5 seconds in order for this code to become active.     The code is logged.
The alarm output is activated.    
17-6 Fuel Shutoff Valve : Current Above Normal     While the output driver is on for 5 seconds, the ECM detected a high current in the circuit for the GSOV for one second.     The code is logged.
The alarm output is activated.
The output driver automatically resets and the output driver continues to try to activate the circuit component.    
17-12 Fuel Shutoff Valve : Failure     The Engine Control Switch (ECS) is placed in the STOP position. The ECM has shut off the fuel to the engine, but the engine rpm does not drop at the expected rate. The deceleration rate must be within rpm of the programmed "Engine Speed Drop Time".     The code is logged.
The alarm output is activated.
The power to the fuel control solenoid remains in the de-energized state and the ECM removes ignition power from the engine.    The ECM contains the logic and the outputs for control of starting the engine and stopping the engine. Some of the logic for starting the engine and for stopping the engine is customer programmable. The logic responds to inputs from the following components: engine control switch, emergency stop switch, remote start switch, data link and other inputs.The ECM outputs a signal to the fuel control solenoid in order to control the fuel shutoff valve. To enable gas flow to the engine, the fuel control solenoid must be energized. The fuel control solenoid may be controlled by the ECM or by the customer equipment. Use this procedure to troubleshoot either configuration.The most likely cause of a diagnostic code is a poor electrical connection or a problem in a wiring harness. The next likely cause may be a problem with the fuel control solenoid. The least likely cause is a problem with the ECM.When the 17-12 Fuel Shutoff Valve failure occurs, the ECM assumes that the fuel shutoff valve did not close. The ECM terminates the ignition. If the fuel control solenoid does not respond to the command, unburned gas will remain in the inlet and exhaust system.Note: Ensure that the unburned gas is purged from the exhaust before restarting the engine. Failure to purge the unburned gas from the engine may result in an explosion in the exhaust piping.The following information describes the systems operation when the GSOV is controlled by the ECM:The ECM sends an output signal