Troubleshooting Guide for the Rotary Position Sensor for Cat® Grade Control on Certain Series E and Series F Excavators {5736} Caterpillar

Excavator

312E (S/N: GAC1-UP; MJD1-UP; PZL1-UP; WEY1-UP)

312F (S/N: KMK1-UP)

313F (S/N: GJD1-UP; DJE1-UP; NLG1-UP; PRG1-UP; HDK1-UP)

314E (S/N: CW81-UP; DKD1-UP; GMD1-UP; ECN1-UP; ZJT1-UP; YCW1-UP)

318E (S/N: DZF1-UP; WZS1-UP)

318F (S/N: HCP1-UP; FFT1-UP; GNX1-UP)

320E (S/N: REE1-UP; SXE1-UP; DFG1-UP; TNJ1-UP; LAK1-UP; WBK1-UP; PNL1-UP; LHN1-UP; AWS1-UP; KLT1-UP; MEW1-UP; SHX1-UP; TEX1-UP; TFX1-UP; NAZ1-UP)

320F (S/N: ZRC1-UP; NHD1-UP; WJJ1-UP; YBM1-UP; TET1-UP; REW1-UP; SFX1-UP)

323E (S/N: RAP1-UP; YRP1-UP; TDW1-UP)

323F (S/N: P391-UP; PLB1-UP; XCF1-UP; YEJ1-UP)

324E (S/N: K321-UP; KTE1-UP; LDG1-UP; PNW1-UP; JCZ1-UP)

326F (S/N: CJ81-UP; HCJ1-UP; XFK1-UP; WGL1-UP)

329E (S/N: H281-UP; RLD1-UP; ZCD1-UP; WJK1-UP; TST1-UP; PLW1-UP; RDX1-UP; PTY1-UP)

329F (S/N: ERL1-UP; GCX1-UP)

330F (S/N: WBA1-UP; LBN1-UP; MBX1-UP)

335F (S/N: KNE1-UP)

336E (S/N: JEA1-UP; RZA1-UP; KED1-UP; YCE1-UP; TEG1-UP; BMH1-UP; FJH1-UP; GTJ1-UP; SSL1-UP; YEP1-UP; CMR1-UP; HDW1-UP; DPX1-UP; BZY1-UP; GNY1-UP; TMZ1-UP)

336F (S/N: B391-UP; TZA1-UP; RKB1-UP; RBC1-UP; YFD1-UP; DKF1-UP; KGH1-UP; ZBJ1-UP; LCL1-UP; NBL1-UP; PFL1-UP; SSN1-UP; LTP1-UP; NBS1-UP; KFT1-UP; DSW1-UP; MTW1-UP; DFY1-UP; WTZ1-UP)

340F (S/N: YBF1-UP; EAR1-UP)

349E (S/N: FJB1-UP; ETC1-UP; DGE1-UP; FKF1-UP; SPG1-UP; TFG1-UP; RGH1-UP; FEJ1-UP; KCN1-UP; MZW1-UP; KFX1-UP; MPZ1-UP; WHZ1-UP)

349F (S/N: BZ21-UP; KEA1-UP; HPD1-UP; SFG1-UP; RAX1-UP)

352F (S/N: SD21-UP; YEG1-UP; A9J1-UP; XAJ1-UP; XAL1-UP; KBP1-UP)

374F (S/N: AT21-UP; AP41-UP; NFJ1-UP; MFL1-UP; DNM1-UP)

390F (S/N: HJD1-UP; TYE1-UP; MGF1-UP; HNG1-UP; FEH1-UP; HSM1-UP; GAY1-UP)

Machine Control and Guidance Products

TERRAIN LOADING (S/N: TFL1-UP)

OEM Excavator Based Specialty Solution

390F OEM (S/N: N641-UP; P4J1-UP)

Introduction

Do not perform any procedure in this Special Instruction until you have read the information and you understand the information.

This Special Instruction provides the troubleshooting procedure for the Rotary Position Sensors on the Cat^® Grade Control (Boom and Stick).

Safety Section

Do not perform any procedure in this Special Instruction until you have read this Special Instruction and you understand this information. Use only proper tools and observe all precautions that pertain to the use of those tools. Failure to follow these procedures can result in personal injury. The following procedures should also be observed.

Work safely. Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs.

A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

Safety precautions and warnings are provided in this instruction and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard.

Therefore, the warnings in this publication and the warnings that are on the product are not all inclusive. Ensure that any tool, procedure, work method, or operating technique you use that is not recommended by Caterpillar is safe.

Ensure that the product will not be damaged or the product will not be made unsafe by the operation, lubrication, maintenance, or repair procedures used.

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Do not operate or work on this machine unless you have read and understand the instructions and warnings in the Operation and Maintenance Manuals. Failure to follow the instructions or heed the warnings could result in injury or death. Contact your Cat dealer for replacement manuals. Proper care is your responsibility.

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Hydraulic oil pressure can remain in the hydraulic systems after the engine and pump have been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic systems. To prevent possible injury, refer to the section, Testing and Adjusting, "Hydraulic System Pressure - Release" before any fitting, hose or component is loosened, tightened, removed or adjusted. When possible, the bucket or attachment must always be lowered to the ground before service is started. When it is necessary for the boom to be in the raised position while tests or adjustments are done, be sure that the boom, stick and bucket or attachment have correct support. The swing lock (if equipped) must be engaged before service is started. Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.

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Accidental machine starting can cause injury or death to personnel working on the machine. To avoid accidental machine starting, turn the battery disconnect switch to the OFF position and remove the key. If the machine is not equipped with a battery disconnect switch, disconnect the battery cables from the battery and tape the battery clamps. Place a do not operate tag at the battery disconnect switch location to inform personnel that the machine is being worked on.

Overview and Functionality

Illustration 1	g06051320
(1) Boom Rotary Position Sensor angle (2) Stick Rotary Position Sensor angle

The Cat^® Grade Control system (CGC) on the E-Series and F-Series Excavators uses two Rotary Position Sensors to measure the relative rotation angle between the two linkages. The Boom Rotary Position Sensor is used to measure the angle (1) between the machine chassis and the Boom. The Stick Rotary Position Sensor measures the angle (2) between the Stick and the Boom. Refer to Illustration 1.

Illustration 2	g06051333
Electrical output

The Rotary Position Sensors provide a Pulse Width Modulated signal (PWM). The Rotary Position Sensors generate a constant frequency of approximately 500-Hz to communicate the angle positions of the Boom or Stick Sensors to the ECM. The duty cycle of the PWM signal changes as the sensor rotates.

Note: The Rotary Position Sensors can be physically rotated 360 degrees. The sensor outputs will only produce a continuous varying duty cycle for 180 degrees. The duty cycle signal range is 5% to 95%. The outputs of the sensor hold at 5% or 95% when rotated pass 90 degrees from the center in either direction. Refer to Illustration 2.

Illustration 3	g06056672
The Boom or the Stick Rotary Position Sensor

The sensor locations can be seen in Illustration 4 and Illustration 5.

Illustration 4	g06051346
Boom Rotary Position Sensor mount plate

Illustration 5	g06051351
The Stick Rotary Position Sensor mount plate with the cover installed (top image) and the cover removed (bottom image).

When troubleshooting an accuracy issue ensure that the Rotary Position Sensors are calibrated properly refer to System Operation, Testing and Adjusting Manual, UENR1725, "Cat^® Grade Control Depth & Slope for E-Series and F-Series Excavators" for complete instructions on how to calibrate and perform an accuracy verification and troubleshooting procedure of the Cat Grade Control system.

Note: Refer to Special Instruction, M0064526, "Troubleshooting Procedure For Bucket Cylinder Position Sensing Unit on Certain Hydraulic Excavators Equipped With Cat^® Grade Control", when the Diagnostic Code: 1956 (FMI 3 and FMI 4) is present and also on how to test and validate the accuracy of the front Position Sensing Cylinder (PSC) unit.

Troubleshooting Procedure

Isolating the Problem

Before troubleshooting the Rotary Position Sensors on the machine, ensure that the machine display is showing an angle value for the Boom and Stick Rotary Position Sensors.

Verify the output duty cycle values for the Rotary Position Sensors. Verifying can be done either through the machine display or using a digital multi-meter that can measure duty cycle signals.

Note: If the display shows a value of a duty cycle output from the Rotary Position Sensors, the reading is an indication that the sensor has the proper power supply present on the connector of the sensor. This reading also indicates that there is a proper connection from the duty cycle output of the sensor to the Machine Implement ECM.

1. Use the following steps to check the duty cycle from the machine display.
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   Illustration 6	g06055545

   1. From the main menu, navigate to the "Service" menu.

   2. Enter the system password.

   3. Select the "Cat Grade Control System" option in the "Service"menu.
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      Illustration 7	g06055631

   4. Navigate to the "CGC Status" selection and press "OK".

   5. Navigate to the "CGC System Sensors" menu option and select "OK".

   6. Monitor the duty cycle of the Boom or Stick. When the Boom or the Stick goes through a full range of motion, notice that the values change on the machine display. The values change as follows:

      • The Boom angle duty cycle value should decrease as the Boom is raised. The Boom angle duty cycle value should increase if the Boom is lowered.

      • The Stick angle duty cycle value increases as the Stick is extended. The Stick angle duty cycle value decreases as the Stick is curled in.

      • There is a continuous value in both sensors while the Boom and Stick are in motion. When the Boom and Stick are not in motion, the value should remain constant.

      • The value should read continuously on the machine display without breaks between the readings.

2. Use a digital multi-meter (DMM) that can measure the duty cycle signal while the Boom or the Stick is in motion. Refer to Step 8 in the "FMI-3 Failure Mode" section.

Diagnostic Codes and Failure Modes

There are two failure mode identifiers (FMI-3 and FMI-4) and four diagnostic codes that relate to the Rotary Position Sensors.

Note: The other failure mode that is related to the Cat Grade Control system is FMI-13 (3423-13 Grade Control System: Out of Calibration). Refer to Systems Operation, Testing and Adjusting Manual, UENR1725, "Cat^® Grade Control Depth & Slope for E-Series and F-Series Excavators" for complete instruction and information on the calibration of the Cat Grade Control system if needed.

The following are possible causes for an FMI-3 diagnostic code:

• 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 power circuit.

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

• The Cat^® Grade Control system has been activated in Cat ET when there are no components installed on the machine.

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

The possible causes for an FMI-4 diagnostic code are the following:

• 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.

Troubleshooting Steps for the Rotary Position Sensor Failure Modes

FMI-3 Failure Mode

1. Before troubleshooting the machine, ensure that the machine is secured and in safe service conditions.

2. Visually inspect the sensors and machine harness wires to ensure proper installation.

3. Disconnect the machine side harness that connects to the Boom or Stick Rotary Position Sensor not showing a value on the machine display.

4. With the key switch on, use a digital multi-meter (DMM) to measure the voltage between pin A and pin B. The voltage between these pins should be 24 V.

5. Pin A is the positive power supply. Pin B is the ground. Refer to Table 3 for connector contact descriptions.

6. If there is a power supply present, connect the sensor to the machine harness. Insert the digital voltmeter leads in the back of the connector and measure the voltages between pin A and pin B. Ensure that the power supply is still present (24 V). Ensure that there is no significant drop or voltage disappearance between pin A and pin B. If the sensor power supply is still present and there is no significant drop in value, proceed to Step 7.

   Note: A significant drop or disappearance of the power supply (voltage) is an indication of internal shortages or a failure of the sensor circuit.

   If there is no power supply present, turn the machine key switch off. Ensure that the machine is in a safe condition to be serviced. Perform a resistance check on the sensor power supply circuit wires using an ohmmeter. Refer to the machine schematic for more details on the sensor power circuit.

7. Ensure that the power supply is on the connector of the Rotary Position Sensor. Ensure that the power supply is in the right order with +24V on pin A and pin B is grounded. After ensuring the power supply is present, measure the output duty cycle from the Rotary Position Sensor.

8. Use a digital multi-meter (DMM) that can measure the frequency of the duty cycle output from the Boom or Stick Rotary Position Sensor. There are two ways to test the Cat^® Grade Control system Rotary Position Sensors using a DMM:

   • Test the Rotary Position Sensor while installed on the machine and connected to the machine harness connector. Insert one of the digital multi-meter (DMM) leads on the back of the machine harness or the sensor connector pin C (the duty cycle output). Insert the other lead in the back of the same connector pin B ground (GND). Put the sensor through a full range of motion and visually monitor the digital multi-meter (DMM) duty cycle reading behaviors.

   Note: To put the Rotary Position Sensor through a full range of motions, fully raise and then lower the Boom all the way down. Fully extend the Stick and then curl it inwards.

   • Test the Rotary Position Sensor outside (uninstalled) of the machine (bench test). To accomplish this procedure successfully, an external 24 V power supply is needed to provide power to the sensor. Connect pin A to the +24V (positive) power supply and pin B to the ground (GND) power supply. After connecting the power supply to the sensor, connect the digital multi-meter (DMM) leads to pin C (the duty cycle) and pin B (GND) to monitor the output duty cycle signal from the sensor while physically rotating the sensor. Read the output changes of the duty cycle and observe the behavior of the signal.

   A sensor is out of calibration if the Boom or the Stick is in motion and the duty cycle readings on the machine display of any of the sensors (Boom or Stick) holds the read value at any given point while the digital multi-meter is still continuously reading or changing the duty cycle of that sensor. This is an indication that a minimum or maximum has been reached of that sensor calibration in the Implement Machine ECM. A calibration of that sensor is needed.

   Note: This condition might not create a fault mode or diagnostic code: FMI-13 (2423-13) Grade Control System out of calibration. Comparing values from both the display and the duty cycle using a digital multi-meter (DMM) is a helpful step for troubleshooting the system and observing the Rotary Position Sensor real-time output values.

   Note: Measuring a duty cycle from the sensors indicates that there is (+24 V) positive power supply on pin A and that pin B is grounded.

FMI-4 Failure Mode

1. Replace the Rotary Position Sensor if there is no duty cycle on pin C when both of the following conditions are present:

   • The machine key switch is on.

   • There is a power supply on the Rotary Position Sensor connector pin A (+24V) and pin B is grounded (GND).

   Refer to Special Instruction, REHS7312, "Instructions for Installing Rotary Position Sensor for Cat^® Grade Control on Certain Series E and Series F Excavators" for complete instructions on replacing or reinstalling the Rotary Position Sensors. Refer to System Operation, Testing and Adjusting Manual, UENR1725, "Cat^® Grade Control Depth & Slope for E-Series and F-Series Excavators" for instructions on how to calibrate the replaced sensor and the Cat^® Grade Control system.

2. Use the following steps if there is a power supply present on the machine harness and a duty cycle present throughout the range of motion of the sensor:

   1. Turn the key switch off.

   2. Secure the machine and follow all safety steps prior to servicing the machine.

   3. Perform a resistance check of the signal wire to the machine ECM. Refer to Table 3.

3. If all troubleshooting steps have been completed and checked, replace the Cat^® Grade Control ECM.

   Note: Failure of the Machine Implement ECM is highly unlikely.

4. Reflash the ECM and calibrate the Cat^® Grade Control system.

   Note: The latest flash software file for the Machine Implement ECM can be obtained from SIS web (http://sisweb.cat.com).

5. Retest the Cat^® Grade Control system. Ensure that there are no codes present and the Cat^® Grade Control system is functioning properly.

Illustration 8	g06052495
Pin positions on sensor

Replacing or Reinstalling the Boom or Stick Rotary Position Sensors

Illustration 9	g06052519
Boom Rotary Position Sensor (4) Wiring (5) Flat side of shaft

Illustration 10	g06052529
Stick Rotary Position Sensor (4) Wiring (5) Flat side of shaft

Ensure proper installation when the Rotary Position Sensors are replaced or reinstalled. Proper installation is critical to the Cat ^® Grade Control system and the accuracy of the system.

The sensors can be visually verified. Before the linkage arm is connected, ensure that the flat spot on the rotor shaft is facing away from the harness location. Ensure that the three bolt pattern is in the housing of the sensors. Refer to Illustration 9 and Illustration 10.

Note: If the Boom or Stick Rotary Position Sensors are replaced or reinstalled, a calibration of that sensor is required. This calibration is required to ensure proper functionality of the Cat^® Grade Control System.

For complete instructions on how to replace or reinstall the Rotary Position Sensors, refer to Special Instruction, REHS7312, "Instructions for Installing Rotary Position Sensor for Cat^® Grade Control on Certain E and Series F Excavators".

Refer to Systems Operation, Testing and Adjusting Manual, UENR1725, "Cat^® Grade Control Depth & Slope for E-Series and F-Series Excavators" for calibration instructions of Cat^® Grade Control systems.

Note: The PWM of the Rotary Position Sensor can be physically rotated 360 degrees.