374 Excavator Machine Electronic Control System Sensor Signal (PWM)

Table 1
Machine ECM 1 (MID 299)
J1939	CDL	Code Description	System Response
	1968-3	Boom Cylinder Rod End Pressure Sensor: Voltage Above Normal	The boom cylinder cannot be lowered when requested.
	1968-4	Boom Cylinder Rod End Pressure Sensor: Voltage Below Normal	The boom cylinder cannot be lowered when requested.
	1968-8	Boom Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The boom cylinder cannot be lowered when requested.
	1969-3	Boom Cylinder Head End Pressure Sensor: Voltage Above Normal	The boom cylinder cannot be raised when requested.
	1969-4	Boom Cylinder Head End Pressure Sensor: Voltage Below Normal	The boom cylinder cannot be raised when requested.
	1969-8	Boom Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The boom cylinder cannot be raised when requested.
	1970-3	Bucket Cylinder Rod End Pressure Sensor: Voltage Above Normal	The bucket open functions may be inoperable.
	1970-4	Bucket Cylinder Rod End Pressure Sensor: Voltage Below Normal	The bucket open functions may be inoperable.
	1970-8	Bucket Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket open functions may be inoperable.
	1971-3	Bucket Cylinder Head End Pressure Sensor: Voltage Above Normal	The bucket close functions may be inoperable.
	1971-4	Bucket Cylinder Head End Pressure Sensor: Voltage Below Normal	The bucket close functions may be inoperable.
	1971-8	Bucket Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket close functions may be inoperable.
	1972-8	Stick Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The stick cylinder cannot be raised when requested.
	1973-3	Stick Cylinder Head End Pressure Sensor: Voltage Above Normal	The stick cylinder cannot be lowered when requested.
	1973-4	Stick Cylinder Head End Pressure Sensor: Voltage Below Normal	The stick cylinder cannot be lowered when requested.
	1973-8	Stick Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The stick cylinder cannot be lowered when requested.
	1974-3	Left Swing Pressure Sensor: Voltage Above Normal	Swing may not function correctly.
	1974-4	Left Swing Pressure Sensor: Voltage Below Normal	Swing may not function correctly.
	1974-8	Left Swing Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	Swing may not function correctly.
	1975-3	Right Swing Pressure Sensor: Voltage Above Normal	Swing may not function correctly.
	1975-4	Right Swing Pressure Sensor: Voltage Below Normal	Swing may not function correctly.
	1975-8	Right Swing Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	Swing may not function correctly.
	2265-3	Hydraulic Pump #1 Outlet Pressure Sensor: Voltage Above Normal	The outlet pressure of the pump will be monitored by the #2 outlet pressure sensor.
	2265-4	Hydraulic Pump #1 Outlet Pressure Sensor: Voltage Below Normal	The outlet pressure of the pump will be monitored by the #2 outlet pressure sensor.
	2265-8	Hydraulic Pump #1 Outlet Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The outlet pressure of the pump will be monitored by the #2 outlet pressure sensor.
	2266-3	Hydraulic Pump #2 Outlet Pressure Sensor: Voltage Above Normal	The outlet pressure of the pump will be monitored by the #1 outlet pressure sensor.
	2266-4	Hydraulic Pump #2 Outlet Pressure Sensor: Voltage Below Normal	The outlet pressure of the pump will be monitored by the #1 outlet pressure sensor.
	2266-8	Hydraulic Pump #2 Outlet Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The outlet pressure of the pump will be monitored by the #1 outlet pressure sensor.
	2474-3	Left Joystick Forward/Reverse Position Sensor: Voltage Above Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2474-4	Left Joystick Forward/Reverse Position Sensor: Voltage Below Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2474-8	Left Joystick Forward/Reverse Position Sensor: Abnormal Frequency, Pulse Width, or Period	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2475-3	Right Joystick Forward/Reverse Position Sensor: Voltage Above Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2475-4	Right Joystick Forward/Reverse Position Sensor: Voltage Below Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2475-8	Right Joystick Forward/Reverse Position Sensor: Abnormal Frequency, Pulse Width, or Period	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2476-3	Left Joystick Left/Right Position Sensor: Voltage Above Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2476-4	Left Joystick Left/Right Position Sensor: Voltage Below Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2476-8	Left Joystick Left/Right Position Sensor: Abnormal Frequency, Pulse Width, or Period	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2477-3	Right Joystick Left/Right Position Sensor: Voltage Above Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2477-4	Right Joystick Left/Right Position Sensor: Voltage Below Normal	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	2477-8	Right Joystick Left/Right Position Sensor: Abnormal Frequency, Pulse Width, or Period	The signal for the joystick function is not valid, the signal is not recognized by the ECM.
	4576-3	Bucket Angle Sensor: Voltage Above Normal	The bucket functions may be inoperable.
	4576-4	Bucket Angle Sensor: Voltage Below Normal	The bucket functions may be inoperable.
	4576-8	Bucket Angle Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket functions may be inoperable.
	5333-3	Swing Motor Angle Sensor Signal #1: Voltage Above Normal	The swing functions may be inoperable.
	5333-4	Swing Motor Angle Sensor Signal #1: Voltage Below Normal	The swing functions may be inoperable.
	5333-8	Swing Motor Angle Sensor Signal #1: Abnormal Frequency, Pulse Width, or Period	The swing functions may be inoperable.
	5334-3	Swing Motor Angle Sensor Signal #2: Voltage Above Normal	The swing functions may be inoperable.
	5334-4	Swing Motor Angle Sensor Signal #2: Voltage Below Normal	The swing functions may be inoperable.
	5334-8	Swing Motor Angle Sensor Signal #2: Abnormal Frequency, Pulse Width, or Period	The swing functions may be inoperable.

Pulse Width Modulation (PWM) is a technique for controlling analog circuits with digital outputs. PWM is employed in various applications ranging from measurement to communication with the Electronic Control Module (ECM). The duty cycle of a square wave is modulated to encode a specific analog signal level. The duty cycle is the ratio of the on-time to the period. The modulating frequency is the inverse of the period. The duty cycle is programmed into the software of the ECM. The engineer (or programmer) sets the period in the on-chip timer counter that provides the modulating square wave. The engineer sets the direction of the PWM output along with the on-time in the PWM control register.

One of the advantages of the PWM sensor is that the signal is digital from the ECM to the controlled system. No digital to analog conversion is necessary. By using a digital signal, noise effects are minimized. Noise affects a digital signal if the noise can change a logic 1 to a logic 0 or a logic 0 to a logic 1.

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Illustration 1	g06561756
Machine ECM 1 PWM Sensors

The preceding diagrams are simplified schematics of the Machine ECM 1 connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Machine ECM 2

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the solenoid valves of the machine.

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Table 2
Machine ECM 2 (MID 299)
J1939	DTC	Code Description	System Response
	1129-3	Right Side Attachment Pedal Sensor: Voltage Above Normal	The signal for the right side attachment pedal is not valid, the signal is not recognized by the ECM.
	1129-4	Right Side Attachment Pedal Sensor: Voltage Below Normal	The signal for the right side attachment pedal is not valid, the signal is not recognized by the ECM.
	1129-8	Right Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period	The signal for the right side attachment pedal is not valid, the signal is not recognized by the ECM.
	1130-3	Left Side Attachment Pedal Sensor: Voltage Above Normal	The left side attachment pedal functions may be inoperable.
	1130-4	Left Side Attachment Pedal Sensor: Voltage Below Normal	The left side attachment pedal functions may be inoperable.
	1130-8	Left Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period	The left side attachment pedal functions may be inoperable.
	1970-3	Bucket Cylinder Rod End Pressure Sensor: Voltage Above Normal	The bucket open functions may be inoperable.
	1970-4	Bucket Cylinder Rod End Pressure Sensor: Voltage Below Normal	The bucket open functions may be inoperable.
	1970-8	Bucket Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket open functions may be inoperable.
	1980-3	Attachment #1 Cylinder Rod End Pressure Sensor: Voltage Above Normal	The attachment #1 rod end functions may be inoperable.
	1980-4	Attachment #1 Cylinder Rod End Pressure Sensor: Voltage Below Normal	The attachment #1 rod end functions may be inoperable.
	1980-8	Attachment #1 Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The attachment #1 rod end functions may be inoperable.
	1981-3	Attachment #1 Cylinder Head End Pressure Sensor: Voltage Above Normal	The attachment #1 head end functions may be inoperable.
	1981-4	Attachment #1 Cylinder Head End Pressure Sensor: Voltage Below Normal	The attachment #1 head end functions may be inoperable.
	1981-8	Attachment #1 Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The attachment #1 head end functions may be inoperable.
	4576-3	Bucket Angle Sensor: Voltage Above Normal	The bucket functions may be inoperable.
	4576-4	Bucket Angle Sensor: Voltage Below Normal	The bucket functions may be inoperable.
	4576-8	Bucket Angle Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket functions may be inoperable.
	5235-3	Right Joystick Thumbwheel #1 Position Sensor: Voltage Above Normal	The right joystick thumbwheel #1 functions may be inoperable.
	5235-4	Right Joystick Thumbwheel #1 Position Sensor: Voltage Below Normal	The right joystick thumbwheel #1 functions may be inoperable.
	5235-8	Right Joystick Thumbwheel #1 Position Sensor: Abnormal Frequency, Pulse Width, or Period	The right joystick thumbwheel #1 functions may be inoperable.
	5236-3	Right Joystick Thumbwheel #2 Position Sensor: Voltage Above Normal	The right joystick thumbwheel #2 functions may be inoperable.
	5236-4	Right Joystick Thumbwheel #2 Position Sensor: Voltage Below Normal	The right joystick thumbwheel #2 functions may be inoperable.
	5236-8	Right Joystick Thumbwheel #2 Position Sensor: Abnormal Frequency, Pulse Width, or Period	The right joystick thumbwheel #2 functions may be inoperable.
	5237-3	Left Joystick Thumbwheel #1 Position Sensor: Voltage Above Normal	The left joystick thumbwheel #1 functions may be inoperable.
	5237-4	Left Joystick Thumbwheel #1 Position Sensor: Voltage Below Normal	The left joystick thumbwheel #1 functions may be inoperable.
	5237-8	Left Joystick Thumbwheel #1 Position Sensor: Abnormal Frequency, Pulse Width, or Period	The left joystick thumbwheel #1 functions may be inoperable.
	5238-3	Left Joystick Thumbwheel #2 Position Sensor: Voltage Above Normal	The left joystick thumbwheel #2 functions may be inoperable.
	5238-4	Left Joystick Thumbwheel #2 Position Sensor: Voltage Below Normal	The left joystick thumbwheel #2 functions may be inoperable.
	5238-8	Left Joystick Thumbwheel #2 Position Sensor: Abnormal Frequency, Pulse Width, or Period	The left joystick thumbwheel #2 functions may be inoperable.
	5332-3	Left Travel Pedal Position Sensor: Voltage Above Normal	The left travel functions may be inoperable.
	5332-4	Left Travel Pedal Position Sensor: Voltage Below Normal	The left travel functions may be inoperable.
	5332-8	Left Travel Pedal Position Sensor: Abnormal Frequency, Pulse Width, or Period	The left travel functions may be inoperable.
	5352-3	Right Travel Pedal Position Sensor: Voltage Above Normal	The right travel functions may be inoperable.
	5352-4	Right Travel Pedal Position Sensor: Voltage Below Normal	The right travel functions may be inoperable.
	5352-8	Right Travel Pedal Position Sensor: Abnormal Frequency, Pulse Width, or Period	The right travel functions may be inoperable.

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Illustration 2	g06561913
Machine ECM 2 PWM Sensors

The preceding diagram is a simplified schematic of the Machine ECM 2 connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Diagnostic Trouble Code Procedure

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Table 3
Required Tools
Tool	Part Number	Description	Qty
T1	146-4080⁽¹⁾	Digital Multimeter Group	1
	8T-3224	Needle Tip Group	1
	7X-1710	Multimeter Probe Group	1
	8T-8726	Cable Assembly (Three Pin) (3-Pin Breakout)	1
T2	JERD2129	Cat^® Electronic Technician (Cat ET)	1
		Windows-based PC	1
	538-5051	Communication Adapter Gp	1
T3	6V-4148	Connector Repair Kit (Sure Seal)	1
T4	190-8900	Connector Field Repair Kit (Deutsch)	1
T5	175-3700	Connector Repair Kit Deutsch DT	1

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⁽¹⁾	This multimeter can use an RS232C cable to connect to a Laptop computer or Dataview tool gp for troubleshooting.

Prior to beginning this procedure, use Cat^® Electronic Technician (Cat ET) Service Tool or the machine monitors to check for an active DTC 41 code. The DTC 41 indicates a failure of the 8 VDC power supply on the ECM. If the code is present, refer to the Sensor Supply - Test chapter to correct this problem before continuing. For transducers powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.

Inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.

Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.

FMI 3 diagnostic code, proceed to "FMI 3".
FMI 4 diagnostic code, proceed to "FMI 4".
FMI 8 diagnostic code, proceed to "FMI 8".

FMI 3

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Table 4
Check The Voltage At The Sensor
Troubleshooting Test Steps	Values	Results
1. Turn the start switch and disconnect switch ON. 2. Refer to the schematic to determine the voltage source for the sensor. 3. At the machine harness connector for the sensor, insert 7X-1710 multimeter probes along the contact of the sensor supply and along frame ground. 4. At the sensor harness connector, measure voltage between the sensor supply and frame ground.	Voltage reading is correct for the sensor.	Result: The voltage reading is correct for the sensor. Proceed to "Check The Harness For An Open" Table 5. Result: The voltage is NOT correct for the sensor. Repair: Examine all the connectors that are in the circuit. Ensure that the connections are clean, secure, and are in good condition. Repair or replace the machine harness. Proceed to "Check If The Diagnostic Code Remains" Table 7.

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Table 5
Check The Harness For An Open
Troubleshooting Test Steps	Values	Results
1. The start switch and the disconnect switch remain in the OFF position. 2. Disconnect the machine harness connector from the sensor. 3. At the machine harness connector for the sensor, connect a jumper wire between the sensor return contact and signal contact. 4. Turn the start switch and disconnect switch ON. 5. Observe the status of the diagnostic code.	The diagnostic code changes from an FMI 3 to an FMI 4.	Result: The diagnostic code changes from an FMI 3 to an FMI 4. The sensor has failed. Repair: Replace the sensor. Proceed to "Check If The Diagnostic Code Remains" Table 7. Result: The diagnostic code does not change from an FMI 3 to an FMI 4. Proceed to "Check Signal Circuit For A Short to +Battery" Table 6.

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Table 6
Check Signal Circuit For A Short to +Battery
Troubleshooting Test Steps	Values	Results
1. Turn the start switch and the disconnect switch to the OFF position. 2. Disconnect the ECM harness connectors. The sensor harness connector remains disconnected. 3. Remove the jumper wire that was installed in the previous test step. 4. At the ECM harness connector, measure the resistance between the signal contact and all other +battery circuits used in the ECM harness connectors.	Each resistance is greater than 5K Ω.	Result: Each resistance is greater than 5K Ω. The harness circuit is correct. Proceed to "Check If The Diagnostic Code Remains" Table 7. Result: The resistance is less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the circuit with the low-resistance measurement. Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit. Proceed to "Check If The Diagnostic Code Remains" Table 7.

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Table 7
Check If The Diagnostic Code Remains
Troubleshooting Test Steps	Values	Results
1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the start switch and the disconnect switch ON. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock. 6. Check if the diagnostic code is active.	The diagnostic code is no longer present.	Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

FMI 4

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Table 8
Check The Sensor
Troubleshooting Test Steps	Values	Results
1. Turn the disconnect switch and the start switch to the ON position. 2. Disconnect the sensor from the machine harness. 3. Observe the status of the diagnostic code as the sensor is disconnected from the harness.	The code changes from an FMI 4 to an FMI 3 when the sensor is disconnected.	Result: The code changes from an FMI 4 to an FMI 3 when the sensor is disconnected. The sensor has failed. Repair: Replace the sensor. Proceed to "Check If The Diagnostic Code Remains" Table 10. Result: The FMI 4 diagnostic code remains active when sensor is disconnected. The sensor is not the cause of the problem. Proceed to "Check The Signal Circuit For A Short To Ground" Table 9.

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Table 9
Check The Signal Circuit For A Short To Ground
Troubleshooting Test Steps	Values	Results
1. Turn the start switch and the disconnect switch to the OFF position. 2. Disconnect the harness connectors from the ECM. The sensor remains disconnected from the machine harness. 3. At the ECM harness connector, measure the resistance between the sensor signal contact and all possible sources of ground.	All resistance values are greater than 5K Ω.	Result: All resistance values are greater than 5K Ω. The harness circuit is correct. Proceed to "Check If The Diagnostic Code Remains" Table 10. Result: One or more readings are less than 5 Ω. A short circuit exists between the signal circuit . Repair: Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit. Proceed to "Check If The Diagnostic Code Remains" Table 10.

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Table 10
Check If The Diagnostic Code Remains
Troubleshooting Test Steps	Values	Results
1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the start switch and the disconnect switch to the ON position. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock . 6. Check if the diagnostic code is active.	The diagnostic code is no longer present.	Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

FMI 8

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Table 11
Check The Signal Of The Sensor
Troubleshooting Test Steps	Values	Results
1. Turn the start switch and disconnect switch to the OFF position. 2. At the back of the harness connector for the sensor, insert multimeter probes along the signal contact and return contact. Note: Use Cat^® Electronic Technician (Cat^® ET) Service Tool if access to the sensor while operating the machine, is not safe. 3. Turn the disconnect switch and the start switch to the ON position. 4. Monitor the signal of the sensor with a digital multimeter. 5. Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range. Note: Refer to the table above for the proper signal.	The signal from the sensor responds in the manner that is described in the table above.	Result: The signal from the sensor responds correctly. The sensor is operating correctly. Proceed to "Check For An Open In The Signal Circuit" Table 12. Result: The signal from the sensor does not respond correctly. The sensor is not operating correctly. Repair: Replace the sensor. Proceed to "Check If The Diagnostic Code Remains" Table 13.

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Table 12
Check For An Open In The Signal Circuit
Troubleshooting Test Steps	Values	Results
1. The start switch and the disconnect switch remain in the OFF position. 2. Disconnect the machine harness connector from the sensor. 3. At the machine harness connector for the sensor, connect a jumper wire between the return contact and signal contact . 4. Disconnect the machine harness connectors J1 and J2 from the ECM. 5. At the ECM harness connector, measure the resistance between the signal contact and return contact.	The reading is less than 5 Ω.	Result: The measurement is less than 5 Ω. The signal and return circuit are correct. Proceed to "Check If The Diagnostic Code Remains" Table 13. Result: The measurement is greater than 5K Ω. The signal circuit in the harness is open. Repair: Repair or replace the machine harness. Proceed to "Check If The Diagnostic Code Remains" Table 13.

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Table 13
Check If The Diagnostic Code Remains
Troubleshooting Test Steps	Values	Results
1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the start switch and the disconnect switch to the ON position. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock lever. 6. Check if the diagnostic code is active.	The diagnostic code is no longer present.	Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.