374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Signal (PWM) - Test Caterpillar


Sensor Signal (PWM) - Test
`
1.1. Machine ECM
2.1. Implement ECM 1
3.1. Implement ECM 2
4.1. Diagnostic Trouble Code Procedure

Machine ECM

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

Table 1
Machine ECM (MID 299) 
DTC  Code Description  System Response 
1125-3  Left Hand Lever Forward/Backward Position Sensor: Voltage Above Normal  Machine will not operate as requested. 
1125-4  Left Hand Lever Forward/Backward Position Sensor: Voltage Below Normal  Machine will not operate as requested. 
1125-8  Left Hand Lever Forward/Backward Position Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
1126-3  Left Hand Lever Left/Right Position Sensor: Voltage Above Normal  Machine will not operate as requested. 
1126-4  Left Hand Lever Left/Right Position Sensor: Voltage Below Normal  Machine will not operate as requested. 
1126-8  Left Hand Lever Left/Right Position Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
1127-3  Right Hand Lever Forward/Backward Position Sensor: Voltage Above Normal  Machine will not operate as requested. 
1127-4  Right Hand Lever Forward/Backward Position Sensor: Voltage Below Normal  Machine will not operate as requested. 
1127-8  Right Hand Lever Forward/Backward Position Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
1128-3  Right Hand Lever Left/Right Position Sensor: Voltage Above Normal  Machine will not operate as requested. 
1128-4  Right Hand Lever Left/Right Position Sensor: Voltage Below Normal  Machine will not operate as requested. 
1128-8  Right Hand Lever Left/Right Position Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
1129-3  Right Side Attachment Pedal Sensor: Voltage Above Normal  The ECM will deactivate the attachment pedal. 
1129-4  Right Side Attachment Pedal Sensor: Voltage Below Normal  The ECM will deactivate the attachment pedal. 
1129-8  Right Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period  The ECM will deactivate the attachment pedal. 
1130-3  Left Side Attachment Pedal Sensor: Voltage Above Normal  The ECM will deactivate the attachment pedal. 
1130-4  Left Side Attachment Pedal Sensor: Voltage Below Normal  The ECM will deactivate the attachment pedal. 
1130-8  Left Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period  The ECM will deactivate the attachment pedal. 
1178-3  Machine Overload Warning Pressure Sensor: Voltage Above Normal  Overload warning detection will be disabled. 
1178-4  Machine Overload Warning Pressure Sensor: Voltage Below Normal  Overload warning detection will be disabled. 
1178-8  Machine Overload Warning Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  Overload warning detection will be disabled. 
1657-3  Left Joystick Thumbwheel: Voltage Above Normal
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
1657-4  Left Joystick Thumbwheel: Voltage Below Normal
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
1657-8  Left Joystick Thumbwheel: Abnormal Frequency, Pulse Width, or Period
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
1658-3  Right Joystick Thumbwheel: Voltage Above Normal
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
1658-4  Right Joystick Thumbwheel: Voltage Below Normal
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
1658-8  Right Joystick Thumbwheel: Abnormal Frequency, Pulse Width, or Period
(1) 
The ECM will deactivate the thumbwheel function of the joystick. 
2263-3  Right Travel Pressure Sensor: Voltage Above Normal  Travel will not operate as requested. 
2263-4  Right Travel Pressure Sensor: Voltage Below Normal  Travel will not operate as requested. 
2263-8  Right Travel Pressure Sensor: Above Normal  Travel will not operate as requested. 
2264-3  Left Travel Pressure Sensor: Voltage Above Normal  Travel will not operate as requested. 
2264-4  Left Travel Pressure Sensor: Voltage Below Normal  Travel will not operate as requested. 
2264-8  Left Travel Pressure Sensor: Above Normal  Travel will not operate as requested. 
2265-3  Hydraulic Pump #1 Outlet Pressure Sensor: Voltage Above Normal  Machine will not operate as requested. 
2265-4  Hydraulic Pump #1 Outlet Pressure Sensor: Voltage Below Normal  Machine will not operate as requested. 
2265-8  Hydraulic Pump #1 Outlet Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
2266-3  Hydraulic Pump #2 Outlet Pressure Sensor: Voltage Above Normal  Machine will not operate as requested. 
2266-4  Hydraulic Pump #2 Outlet Pressure Sensor: Voltage Below Normal  Machine will not operate as requested. 
2266-8  Hydraulic Pump #2 Outlet Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
2899-3  Main Hydraulic Pump #1 Displacement Sensor: Voltage Above Normal  Machine will not operate as requested. 
2899-4  Main Hydraulic Pump #1 Displacement Sensor: Voltage Below Normal  Machine will not operate as requested. 
2899-8  Main Hydraulic Pump #1 Displacement Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
2900-3  Main Hydraulic Pump #2 Displacement Sensor: Voltage Above Normal  Machine will not operate as requested. 
2900-4  Main Hydraulic Pump #2 Displacement Sensor: Voltage Below Normal  Machine will not operate as requested. 
2900-8  Main Hydraulic Pump #2 Displacement Sensor: Abnormal Frequency, Pulse Width, or Period  Machine will not operate as requested. 
3277-3  Swing Pressure Sensor: Voltage Above Normal  Swing system will not operate as requested. 
3277-4  Swing Pressure Sensor: Voltage Below Normal  Swing system will not operate as requested. 
3277-8  Swing Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  Swing system will not operate as requested. 
3798-3  Straight Travel Pressure Sensor: Voltage Above Normal  Travel will not operate as requested when straight travel pedal is used. 
3798-4  Straight Travel Pressure Sensor: Voltage Below Normal  Travel will not operate as requested when straight travel pedal is used. 
3798-8  Straight Travel Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  Travel will not operate as requested when straight travel pedal is used. 
(1) Thumbwheel integrated into joystick, entire joystick must be replaced if sensor fails

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.

Possible Causes for an FMI 3 Diagnostic code are:

  • The sensor has failed.

  • The sensor supply or the ground circuit in the machine harness is open.

  • The signal circuit in the machine harness is shorted to the +battery.

  • The signal circuit in the machine harness is open or the sensor is disconnected.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed.

  • The signal circuit in the machine harness is shorted to ground.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 8 Diagnostic code are:

  • The sensor has failed.

  • Intermittent connections or poor connections.


Illustration 1g06108284
Machine ECM PWM Sensors

Note: The diagram above is simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) for the complete schematic.

Implement ECM 1

Table 2
Implement ECM 1 (MID 432) 
DTC  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 cylinder cannot be raised when requested. 
1970-4  Bucket Cylinder Rod End Pressure Sensor: Voltage Below Normal  The bucket cylinder cannot be raised when requested. 
1970-8  Bucket Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  The bucket cylinder cannot be raised when requested. 
1971-3  Bucket Cylinder Head End Pressure Sensor: Voltage Above Normal  The bucket cylinder cannot be raised when requested. 
1971-4  Bucket Cylinder Head End Pressure Sensor: Voltage Below Normal  The bucket cylinder cannot be raised when requested. 
1971-8  Bucket Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  The bucket cylinder cannot be raised when requested. 

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.

Possible Causes for an FMI 3 Diagnostic code are:

  • The sensor has failed.

  • The sensor supply or the ground circuit in the machine harness is open.

  • The signal circuit in the machine harness is shorted to the +battery.

  • The signal circuit in the machine harness is open or the sensor is disconnected.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed.

  • The signal circuit in the machine harness is shorted to ground.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 8 Diagnostic code are:

  • The sensor has failed.

  • Intermittent connections or poor connections.


Illustration 2g03539916
Implement ECM 1 PWM Sensors

Note: The diagram above is simplified schematic of the Implement ECM 1 connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) for the complete schematic.

Implement ECM 2

Table 3
Implement ECM 2 (MID 433) 
DTC  Code Description  System Response 
1972-3  Stick Cylinder Rod End Pressure Sensor: Voltage Above Normal  The stick cylinder cannot be raised when requested. 
1972-4  Stick Cylinder Rod End Pressure Sensor: Voltage Below Normal  The stick cylinder cannot be raised when requested. 
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 raised when requested. 
1973-4  Stick Cylinder Head End Pressure Sensor: Voltage Below Normal  The stick cylinder cannot be raised when requested. 
1973-8  Stick Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  The stick cylinder cannot be raised when requested. 
1974-3  Left Swing Pressure Sensor: Voltage Above Normal  The swing function will not operate when requested. 
1974-4  Left Swing Pressure Sensor: Voltage Below Normal  The swing function will not operate when requested. 
1974-8  Left Swing Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  The swing function will not operate when requested. 
1975-3  Right Swing Pressure Sensor: Voltage Above Normal  The swing function will not operate when requested. 
1975-4  Right Swing Pressure Sensor: Voltage Below Normal  The swing function will not operate when requested. 
1975-8  Right Swing Pressure Sensor: Abnormal Frequency, Pulse Width, or Period  The swing function will not operate when requested. 

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.

Possible Causes for an FMI 3 Diagnostic code are:

  • The sensor has failed.

  • The sensor supply or the ground circuit in the machine harness is open.

  • The signal circuit in the machine harness is shorted to the +battery.

  • The signal circuit in the machine harness is open or the sensor is disconnected.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed.

  • The signal circuit in the machine harness is shorted to ground.

  • The Machine ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 8 Diagnostic code are:

  • The sensor has failed.

  • Intermittent connections or poor connections.


Illustration 3g03539917
Implement ECM 2 PWM Sensors

Note: The diagram above is simplified schematic of the Implement ECM 2 connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) for the complete schematic.

Diagnostic Trouble Code Procedure

Note: 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 story 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.

Note: Prior to beginning this 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.

Table 4
Troubleshooting Test Steps  Values  Results 
1. Identify Active FMI Code Associated With Sensor Circuit 
Code present 
FMI 3 diagnostic code, proceed to Test Step 2.

FMI 4 diagnostic code, proceed to Test Step 6.

FMI 8 diagnostic code, proceed to Test Step 8. 
Begin Process For FMI 3 Troubleshooting HERE 
2. Check The Control And The Harness

A. Turn key start switch and disconnect switch ON.

B. Disconnect the machine harness from sensor.

C. Refer to the schematic to determine the voltage source for the suspected faulty sensor.

D. Measure voltage between signal and ground contacts at the machine harness connector for the sensor. 

Voltage reading is within range. 
OK - The voltage reading is correct for the suspected faulty sensor.

Proceed to Test Step 3.

NOT OK- The voltage is NOT correct for the circuit.

Repair - Refer to the diagnostic code procedure in this manual for troubleshooting of the power supply. After the power supply procedure is performed, verify the status of the sensor diagnostic code before proceeding.

Proceed to Test Step 14. 
3. Check For An Open In The Sensor Circuit

A. The sensor remains disconnected from the machine harness.

B. Turn the key start switch and the disconnect switch OFF.

C. At the harness connector for the sensor, place a jumper wire between Pin 2 (or Pin B) and Pin 3 (or Pin C). These locations are also referred to as the ground contact and the signal contact.

D. Disconnect J1 and J2 harness connectors from the ECM.

E. At machine harness connector for sensor, measure the resistance from the signal contact to return contact.

F. Gently pull on the wires and move the wires in a circular motion at ECM connector and observe the resistance readings. Repeat the process for the sensor connector. 

The resistance is less than 5 Ω at all times during the manipulation of the harness.. 
OK - The resistance is less than 5 Ω. The signal circuit and the ground circuits of the sensor are not open in the machine harness.

Proceed to Test Step 4.

NOT OK - Resistance reading for the signal circuit or the return circuit is greater than 5 Ω.

Repair: Check the signal circuit or the ground circuit for opens or poor connections.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
4. Check Signal Circuit For A Short To +Battery

A. The Sensor and the ECM are disconnected from the harness.

B. Turn the disconnect switch and the key start switch OFF.

C. Measure the resistance between the signal and +battery contacts of the harness connector for the sensor.
D. At machine harness connector J1 and J2 measure the resistance from signal contact to all possible sources of +battery. 

Resistance greater than 5K Ω for all readings. 
OK - The resistance is greater than 5K Ω. The harness circuit is correct..

Proceed to Test Step 5.

NOT OK- The resistance less than 5 Ω.

Repair: A short exists in the harness between the +battery and signal circuit. Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
5. Check The Harness For An Open

A. The disconnect switch and key start switch are OFF

B. The sensor and ECM disconnected from harness.

C. Connect a jumper wire from the end of the signal wire at the ECM to a known ground.

D. Measure the resistance of the signal wire at ECM. 

Resistance less than 5 Ω. 
OK - The resistance of the signal wire is less than 5 Ω.

Proceed to Test Step 14.

NOT OK - The resistance is greater than 5K Ω. The signal wire is open in the machine harness.

Repair: Repair or replace the harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
Begin Process For FMI 4 Troubleshooting HERE 
6. Check The Sensor

A. With FMI 4 active, disconnect the sensor from the machine harness.

B. Observe Cat® Electronic Technician (Cat ET) Service Tool or the operator monitor for code change as the sensor is disconnected and connected to harness. 

Code changes from FMI 4 to FMI 3. 
OK - The diagnostic changed to FMI 3 when the sensor was disconnected.

Repair: Replace the sensor.

Proceed to Test Step 14.

NOT OK - The FMI 4 diagnostic code remains active when sensor is disconnected. The sensor not the cause of the problem.

Proceed to Test Step 7. 
7. Check The Signal Circuit For A Short To Ground

A. Turn the key start switch and the disconnect switch OFF.

B. Disconnect the J1 harness connector from the ECM.

C. Measure the resistance between the signal contact for sensor and frame ground. 

The resistance is greater than 5K Ω. 
OK - The resistance is greater than 5K Ω. The harness circuit is correct.

Proceed to Test Step 14.

NOT OK - The resistance is less than 5 Ω. A short circuit exists between frame ground and the signal circuit.

Repair: Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
Begin Process For FMI 8 Troubleshooting HERE 
8. Check Harness For An Open

A. Turn the disconnect switch and the key start switch OFF

B. The sensor and ECM are disconnected from the harness.

C. Connect a jumper wire from the end of signal wire at the ECM to a known ground.

D. Measure the resistance of the signal wire at ECM. 

The reading is less than 5 Ω. 
OK - The measurement is less than 5 Ω.

Proceed to Test Step 9.

NOT OK - The measurement is greater than 5K Ω. The signal circuit in the harness is open.

Repair: Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
9. Check The Signal Circuit For A Short To Ground

A. Turn key start switch and disconnect switch OFF.

B. Disconnect J1 harness connector from ECM.

C. Measure resistance between signal contact for sensor and frame ground. 

Reading is greater than 5K Ω. 
OK - Measurement is greater than 5K Ω.

Proceed to Test Step 10.

NOT OK - Measurement is less than 5 Ω. The signal circuit in the harness is shorted to ground.

Repair: Repair or replace the machine harness.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
10. Check The Sensor For A Short To Case

A. Turn the key start switch and the disconnect switch OFF.

B. At the machine harness connector for the sensor, measure the resistance between each pin of sensor (contacts 1, 2, and 3 of the sensor). Connect the ground lead of the meter to an unpainted location on case of sensor . 

The reading is greater than 5K Ω. 
OK - All measurements are greater than 5K Ω.

Proceed to Test Step 11.

NOT OK - A measurement is less than 5 Ω. The sensor has failed..

Repair: Replace the sensor. Confirm that the new sensor corrects the problem.

Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.

Proceed to Test Step 14. 
11. Check The Sensor For A Short To +Battery

A. Disconnect the machine harness at the sensor.

B. Turn the key start switch and the disconnect switch ON.

C. At machine harness connector for J1 connector, measure the voltage between the signal pin of sensor and frame ground. 

The voltage is 0 VDC. 
OK - Voltage is 0 VDC.

Proceed to Test Step 12.

NOT OK - Significant voltage is present in circuit.

Repair: Repair or replace the machine harness.

Proceed to Test Step 14. 
12. Check The Harness For A Short To +Battery

A. Turn the key start switch and the disconnect switch ON.

B. At machine harness connector for sensor, measure the voltage between each pin of sensor and frame ground (contacts 1, 2, and 3). 

The voltage is 0 VDC. 
OK - Voltage is 0 VDC.

Proceed to Test Step 13.

NOT OK - Significant voltage is present in circuit. Circuit shorted to +battery.

Repair: Replace the sensor. Verify that the new sensor corrected the diagnostic code.

Proceed to Test Step 14. 
13. Check The Sensor

A. Turn the key start switch and the disconnect switch ON.

B. Use Cat ET or the operator monitor to confirm the existence of the diagnostic code.

C. Disconnect the sensor from machine harness. 

The diagnostic code is no longer present. 
OK - Diagnostic code is NO longer active. The sensor has failed.

Repair: Replace the sensor. Verify new sensor corrected the diagnostic code.

Proceed to Test Step 14.

NOT OK - The diagnostic code remains active.

Proceed to Test Step 14. 
14. Check If The Diagnostic Code Remains.

A. Turn the key start switch and the disconnect switch ON.

B. Clear all diagnostic codes.

C. Operate the machine.

D. Stop machine and engage the safety lock lever.

E. Check if the diagnostic code for the sensor is active. 

The code for the sensor is NO longer present. 
OK - The diagnostic code does not exist currently. The initial diagnostic code may have been caused by a poor electrical connection or a short at one of the harness connections. Resume machine operation.

STOP.

NOT OK - The diagnostic trouble code has not been corrected.

Repair: Recheck the circuit and perform this procedure again. If the diagnostic code is still active, the Machine 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 procedure in Troubleshooting, "ECM - Replace" to replace the ECM.

STOP. 

Information System:

C4.4 Engines for Caterpillar Built Machines Glossary of Electronic Control Terms
C4.4 Engines for Caterpillar Built Machines Connecting Rod - Inspect
C4.4 Industrial Engine Fuel Related Components in Cold Weather
C15 and C18 On-Highway Engines Valve Mechanism Cover Base - Remove and Install
C280-16 Engine Air Starting Motor - Remove and Install
C280-16 Engine Prelubrication Oil Pump - Remove and Install
Exhaust Balance Valve Causing Regeneration Issues On Certain Tier 4i C13 Engines{1061, 5479}
C11 and C13 On-Highway Engines Compression Brake Lash - Adjust
12M Series 3, 140M Series 3, 160M Series 3, 140, 150 and and 160 Motor Graders Centershift Lock
C15 and C18 On-Highway Engines Front Cover - Remove and Install
C4.4 Engines for Caterpillar Built Machines Connecting Rod - For Use With Spheroidal Graphite Iron (SGI) Crankshaft
C15 and C18 On-Highway Engines Vibration Damper and Pulley - Remove and Install
G3600 A4 Engines Oil Pressure Is High
12M Series 3, 140M Series 3, 160M Series 3, 140, 150 and and 160 Motor Graders Electronic Control (Power Train System)
C13, C15, and C18 Tier 4 Final Engines Turbocharger
C13, C15, and C18 Tier 4 Final Engines Valve Mechanism Cover
G3600 A4 Engines Exhaust Temperature Is High
16M Series 3, 16, 18M Series 3 and 18 Motor Grader Power Train System
G3600 A4 Engines Exhaust Temperature Is Low
C13, C15, and C18 Tier 4 Final Engines Exhaust Combustion (ARD)
G3600 A4 Engines Alternator Problem - Charging Problem and/or Noisy Operation
725C, 725C2, 730C, 730C2 and 730C, 730C2 EJECTOR Articulated Truck Systems Modulating Valve (Transmission Hydraulic Control)
New IGBT Driver For UPSB505 {1401, 4480}
G3600 A4 Engines Electrical Power Supply - Test