SEAL-BUFFER 3338687 - Caterpillar

System Operation Description:Use this procedure to troubleshoot suspect problems with the circuit for the gas shutoff valve.This procedure covers the following diagnostic codes:
17-5 Fuel Shutoff Valve : Current Below Normal
17-6 Fuel Shutoff Valve : Current Above Normal
17-12 Fuel Shutoff Valve : FailureThe Electronic Control Module (ECM) contains the logic and the outputs for control of starting the engine and stopping the engine. The logic for starting and for stopping is customer programmable. The logic responds to inputs from the following components: engine control, emergency stop switch, remote start switch, data link and other inputs.To enable fuel flow to the engine, the gas shutoff valve (GSOV) must be energized. The GSOV may be controlled by the ECM or by the customer's equipment. Use this procedure to troubleshoot either configuration.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.The most likely causes of a diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the GSOV. The least likely cause is a problem with the ECM.A 17-12 diagnostic code is activated after the following sequence of events:
The engine is running.
The ECM receives a signal for stopping the engine.
The ECM removes power from the electrical circuit for the GSOV.
The engine rpm does not drop at least 100 rpm within the time that is specified by the "Engine Speed Drop Time" parameter.When these events occur, the ECM assumes that the GSOV did not close. The ECM terminates the ignition. The ECM also activates a 17-12 diagnostic code. Unburned gas remains in the air inlet and exhaust system.The following information describes the system's operation when the GSOV is controlled by the ECM:The ECM output for the gas shutoff valve is called the "fuel control relay". This output is energize-to-run. The ECM provides +Battery voltage to this output when the logic determines that fuel is required for engine operation. The ECM removes the voltage from this output in order to stop the engine. The gas shutoff valve is de-energized. This stops the fuel flow.There are several possible configurations for wiring the GSOV. Consider the following information:
The circuit for the GSOV must be complete in order for the engine to crank.
The circuit for the GSOV must remain complete in order for the engine to run.
The GSOV can be connected anywhere in the circuit.Some possible configurations are discussed in the following paragraphs.The GSOV is controlled by the customer's equipment. In this case, the circuit for the engine's control system must be a complete path. The circuit must include a resistor. Otherwise, a diagnostic code will be activated and the engine will not start. Illustration 1 is an example of this type of installation.
Illustration 1 g01300262
The GSOV is controlled by the customer's equipment.
The GSOV is controlled by the engine's control system. The engine harness is used for the connection. The customer may supply an additional switch in the electrical circuit for