G3306B Petroleum Generator Set Engines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit for the Gas Shutoff Valve (GSOV). 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
632-5 Engine Fuel Shutoff Valve #1 : Current Below Normal	The Electronic Control Module (ECM) detects a low current in the circuit for the GSOV for 2 seconds. The output driver must be off for 5 seconds in order for this code to become active.	The code is logged. The amber warning lamp is illuminated. The service tool displays "Error Indicator" on the status screen for this parameter.
632-6 Engine Fuel Shutoff Valve #1 : 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 amber warning lamp is illuminated. The service tool displays "Error Indicator" on the status screen for this parameter. The output driver automatically resets and the output driver continues to try to activate the circuit component.
632-7 Engine Fuel Shutoff Valve #1 : Not Responding Properly	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 remains above the crank terminate speed. The engine speed exceeded the crank terminate speed for a period that exceeds the "Engine Speed Drop Time".	The code is logged. The red stop lamp is illuminated. The power to the GSOV 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: ECS, emergency stop switch, remote start switch, data link and other inputs.

The ECM outputs a signal in order to control the solenoid for the GSOV. To enable gas flow to the engine, the GSOV must be energized.

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 solenoid. The least likely cause is a problem with the ECM.

When the 632-7 Engine Fuel Shutoff Valve #1 : Failure occurs, the ECM assumes that the GSOV did not close. The ECM terminates the ignition. If the GSOV does not respond to the ECM command, unburned gas will remain in the air 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 to the solenoid for the GSOV that controls the operation of the GSOV. This output is energize-to-run. During the crank cycle, when the engine speed exceeds 50 rpm, the ECM provides a voltage of +Battery to the output for the GSOV. The solenoid becomes energized. As the valve opens, fuel begins to flow to the engine. The ECM removes the voltage from this output in order to stop the engine. The solenoid for the GSOV becomes de-energized. The fuel flow to the engine is stopped.

Illustration 1	g01920674
Schematic of the circuit for the GSOV

Illustration 2	g01920713
Location of the connectors at the ECM (right front engine view) (1) J1/P1 ECM connectors for the GSOV

Illustration 3	g01921613
Location of the components that are for control of the GSOV (typical location) (2) Solenoid for the GSOV (3) Gas Shutoff Valve (GSOV)

Illustration 4	g01920953
Terminal locations at the P1 ECM connector that are associated with the GSOV (P1-32) Gas shutoff valve (P1-25) Return

Illustration 5	g01415822
Terminal locations at the connector for the GSOV (Terminal A) Gas shutoff valve (Terminal B) Return

Table 2

Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Ensure that the electrical power has been removed from the engine. B. Thoroughly inspect connectors (1) and (2). Also, inspect the connectors for solenoid (3). Refer to Testing and Adjusting, "Electrical Connectors - Inspect" for details. C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the GSOV. D. Check the wiring harnesses for abrasion, for corrosion and for pinch points.	Connectors and Wiring	Result: The electrical connectors and the wiring are OK. Proceed to Test Step 2. Result: The electrical connectors and the wiring are Not OK. Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the problem is resolved.
2. Check for Diagnostic Codes that are Active or Logged A. Remove the electrical power from the engine. B. Connect Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary. C. Restore electrical power to the ECM. Set the engine control to STOP. Note: The 632-5 Engine Fuel Shutoff Valve #1 : Current Below Normal can only be detected when the output for the start command is off. The output is normally off when the engine control is set to STOP and the engine speed is zero rpm. D. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active. F. Initiate an engine start-up. Note: In order for the ECM to check for a 632-6 Engine Fuel Shutoff Valve #1 : Current Above Normal, the sequence for start-up must be initiated. In order for the ECM to check for a 632-7 Engine Fuel Shutoff Valve #1 : Failure, the engine must be shut down after the engine is running. Note: Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active. G. Attempt to start the engine. If the engine starts, set the engine control to STOP after the engine reaches idle speed. Note: Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active.	Codes	Result: No diagnostic codes are active or logged for the GSOV. Repair: There may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting "Electrical Connectors - Inspect". Result: A 632-5 code is active. Repair: The code can be caused by an actual open circuit or by a short circuit to the +Battery. Proceed to Test Step 3. Result: A 632-6 code is active. Repair: There appears to be a short circuit in the circuit for the GSOV. Proceed to Test Step 7. Result: A 632-7 code is active. Repair: The ECM disabled the ignition in order to stop the engine. The GSOV appears to be stuck open. Repair the valve assembly or replace the valve assembly. Verify that the repair eliminates the original problem.
3. Check for a Short Circuit to +Battery in the Harness A. Ensure that no combustible gas is present in the surrounding atmosphere. B. Verify that the engine control is set to STOP. C. Disconnect the connector from the GSOV. D. Use a multimeter to check the voltage at the harness connector for the GSOV.	No Voltage	Result: Voltage is not present at the harness connector for the GSOV. Proceed to Test Step 4. Result: Voltage is present at the harness connector for the GSOV. Proceed to Test Step 6.
4. Create a Short Circuit at the Harness Connector for the Gas Shutoff Valve A. Remove the electrical power from the engine. B. Fabricate a jumper wire that is long enough to create a test circuit at the harness connector for the GSOV. Crimp connector pins to each end of the jumper wire. C. Disconnect the harness connector from the GSOV. D. Install the jumper wire into the two terminals of the harness connector for the GSOV. E. Restore the electrical power to the engine. Set the engine control switch to STOP.	632-6 Code	Result: A 632-6 code is active. Perform the following procedure: - Disconnect the harness connector for the solenoid. - Use a multimeter to measure the coil resistance for the solenoid. Measure the resistance between terminals 1 and 2 at the solenoid connector. - Restore the wiring to the original configuration. - The correct resistance of the coil is approximately 16.5 Ohms. If the condition of the coil is suspect, replace the solenoid. Verify that the original condition is resolved. Result: A 632-5 code is active. Proceed to Test Step 5.
5. Create a Short Circuit at the ECM Connector and Check for Diagnostic Codes A. Verify that the electrical power is removed from the engine. B. Disconnect the J1/P1 and the J2/P2 ECM connectors. C. Fabricate a jumper wire that is long enough to create a test circuit across the ECM connector. Crimp connector sockets to each end of the jumper wire. D. Remove the wires from terminal locations P1-65 and P2-5 at the ECM connector. Install one end of the jumper wire into each of these terminal locations. E. Connect the J1/P1 and the J2/P2 ECM connectors. F. Restore the electrical power to the engine. Set the ECS to the STOP position. Note: The 632-5 Engine Fuel Shutoff Valve #1 : Current Below Normal can only be detected when the output for the start command is off. The output is normally off when the ECS is in the STOP position and the engine speed is zero rpm. G. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active. H. Attempt to start the engine. If the engine starts, set the ECS to the STOP position after the engine reaches idle speed. Note: The 632-6 Engine Fuel Shutoff Valve #1 : Current Above Normal can only be detected when the output for the start command is on. The output is normally on when the ECS is switched from the STOP position to the START position. The output remains on during engine cranking.	635-6 Code	Result: A 632-6 code is active. Repair: The ECM detects the jumper wire that is installed at the P1 and P2 ECM connector. There is an open circuit in the wiring harness between the ECM connector and the harness connector for the GSOV. The problem could be with one of the emergency stop switches. Check for proper operation of the switches. Perform the necessary repairs. Verify that the repair resolves the original problem. Result: A 632-5 code is active. Repair: The ECM did not detect the short circuit. There appears to be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN).
6. Check for a Short Circuit to the +Battery in the Harness Circuit at the ECM Connector A. Remove the electrical power from the engine. B. Disconnect the J1/P1 and the J2/P2 ECM connectors. C. At the P1 and the P2 ECM connectors, use a multimeter to check for a voltage on the harness between terminal locations P1-65 and P2-5. D. Restore the electrical power to the engine. Set the engine control to STOP. E. With the ECS in the STOP position, use a multimeter to check for a voltage on the harness between terminal locations P1-65 and P2-5. F. Remove the electrical power from the engine. G. Connect theJ1/P1 and the J2/P2 ECM connectors.	No Voltage	Result: No voltage is present. Repair: Voltage is present at the GSOV before isolating the harness from the ECM, but is not present after isolating the harness from the ECM. There appears to be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN). Result: Voltage is present. Repair: There is a short to +Battery in the harness between the P2 ECM connector and the harness connector for the GSOV. Repair the harness, when possible. Replace parts, if necessary.
7. Create an Open Circuit at the Gas Shutoff Valve and Check for Codes A. Remove the electrical power from the engine. B. Disconnect the harness connector from the GSOV. C. Restore the electrical power to the engine. Set the engine control to STOP. Note: The 632-5 Engine Fuel Shutoff Valve #1 : Current Below Normal can only be detected when the output for the start command is off. The output is normally off when the ECS is in the STOP position and the engine speed is zero rpm. D. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active. E. Attempt to start the engine. If the engine starts, set the ECS to the STOP position after the engine reaches idle speed. Note: The 632-6 Engine Fuel Shutoff Valve #1 : Current Above Normal can only be detected when the output for the start command is on. The output is normally on when the ECS is switched from the STOP position to the START position. The output remains on during engine cranking.	632-5 Code	Result: A 632-6 code is active. Proceed to Test Step 8. Result: A 632-5 code is active. Repair: There appears to be a problem with the solenoid of the GSOV. Perform the following procedure: - Disconnect the harness connector for the solenoid. - Use a multimeter to measure the coil resistance of the solenoid. Check the resistance between terminals 1 and 2 at the connector for the solenoid. - Restore the wiring to the original configuration. - The correct resistance of the coil is approximately 16.5 Ohms. If the condition of the coil is suspect, replace the solenoid. Verify that the original condition is resolved.
8. Create an Open Circuit at the ECM Connector and Check for Diagnostic Codes A. Remove the electrical power from the engine. B. Use a wire removal tool to remove the wires from terminal locations P1-65 and P2-5 at the ECM connector. C. Restore the electrical power to the engine. Set the ECS to the STOP position. Note: The 632-5 Engine Fuel Shutoff Valve #1 : Current Below Normal can only be detected when the output for the start command is off. The output is normally off when the ECS is in the STOP position and the engine speed is zero rpm. D. Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Wait at least 30 seconds in order for diagnostic codes to become active. E. Attempt to start the engine. If the engine starts, set the ECS to the STOP position after the engine reaches idle speed. Note: The 632-6 Engine Fuel Shutoff Valve #1 : Current Above Normal can only be detected when the output for the start command is on. The output is normally on when the ECS is switched from the STOP position to the START position. The output remains on during engine cranking. F. Remove the electrical power from the engine.	632-5 Code	Result: A 632-5 code is active. Repair: There is a problem with the wiring between the ECM connector and the harness connector that is for the GSOV. Perform the necessary repairs. Verify that the repair resolves the original problem. Result: A 632-6 code is active. Repair: There appears to be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN)