| Event Codes | ||
|---|---|---|
| Code and Description | Conditions which Generate this Code | System Response |
| E192(3) Steering System Malfunction | There is an active diagnostic code for the steering system. | The code is logged. |
| E256(3) Steering Output Detected in Wrong Direction | The machine ECM commands steering in a particular direction but the speed sensor for the steering motor detects motion in the opposite direction. | The code is logged. |
| E257(3) Steering Output Detected with No Command Given | The machine ECM is not commanding any steering, but the speed sensor for the steering motor detects motor speed. | The code is logged. |
| E258(3) No Steering Detected with Command Given | The speed sensor for the steering motor does not detect motor speed in response to a steering command from the machine ECM. | The code is logged. |
- The oil level in the hydraulic tank is low.
- Steering pump controls
- Low charge pump pressure
- Crossover relief and makeup valves
- Charge pump flow rate low
- Piston pump (rotating group) flow rate
- Steering pump case drain flow rate
- The pump or the steering motor has failed.
Note: Care must be taken in order to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the machine. You must be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component that contains fluid. Dispose of all fluids according to local regulations.
The Oil Level In The Hydraulic Tank Is Low
The hydraulic oil tank has a sight gauge on the outside of the tank. Check the hydraulic oil level with the machine on level ground and the engine OFF. If oil is NOT seen in the sight glass, the hydraulic oil level is low.
If the hydraulic oil level is low, check for oil leakage.
Inspect the following items of the hydraulic tank for oil leakage:
- All of the weld joints
- All of the bolted covers and components
- All fittings
- All hose flange connections
Oil may leak out of the system if the welds are damaged, if covers and components have seals or gaskets installed improperly, or if the bolts and fittings are improperly torqued. Correct any of the problems that are found. Fill the hydraulic tank with the correct oil. Monitor the tank in order to ensure that the leaks have been stopped.
Refer to Operation and Maintenance Manual, SEBU9127, "Hydraulic System Oil Level - Check".
Note: Ensure that the strainer is present in the filler tube before adding the recommended hydraulic oil.
The Steering Pump Controls Are Suspect
With the monitoring system or Caterpillar Electronic Technician (Cat ET), check for event codes associated with the steering lever position sensors.
Any type of failure with the steering position sensors will result in a "Level 3 Warning" indicating the machine needs to be shut down immediately in a safe manner and in a safe position before damage to the machine or injury to personnel occurs.
Note: Refer to 1 for event codes.
If an event code for the steering system is logged, continue with the following procedures.
- Check the monitoring system or Cat ET for any fault codes related to "Steering Position Sensor 1", "Steering Position Sensor 2", or "Steering Position Sensor 3".
Ensure that a problem with the steering lever position sensors is not causing the steering pump to operate improperly. If the signals from the steering position sensors are incorrect, the ECM may not be commanding the solenoid to energize properly, and/or the ECM may not be commanding the solenoid to de-energize properly. Correct any problems with these components, then check to see if the symptom is resolved.
With the monitoring system, perform the calibration routine for the "Steering Control Position Sensors".
- With the monitoring system , perform the calibration routine for the "Steering Control Position Sensors". After you enter the "Service Password" , the calibration procedure may be accessed via "Service/Calibrations/Steering Calibrations/Steering Control Position Sensors".
This procedure will calibrate all three-position sensors so that the machine ECM can properly interpret the signals from the sensors and correctly control the steering pump control solenoids.
If these sensors are not properly calibrated, the sensors may be falsely sending signals to the ECM to steer with no steering request, or sending signals in one steering direction but not the other.
- With the monitoring system, check the signal "Duty Cycle" from the steering lever position sensors.
View the status of the steering lever position sensors in order to ensure that the signals are accurate.
The active real-time status of these sensors may be viewed at the following location: "Service/System Status/Steering/Steer Pos Sensor 1 Duty Cycle, Steer Pos Sensor 2 Duty Cycle, Steer Pos Sensor 3 Duty Cycle".
All three sensors should be sending a relatively close signal, as follows:
- NO STEER - 49% - 51% Duty Cycle
- LEFT STEER - 8% - 10% Duty Cycle
- RIGHT STEER - 88% - 90% Duty Cycle
If the sensors have been calibrated and are still sending incorrect signals, and if no electrical problems are found in the sensor circuits, one or more of the sensors are bad and must be replaced.
Note: Note: All three of the sensors are packaged together as an assembly therefore all three of the sensors must be replaced.
After replacing the sensors, repeat Step 2 then retest for the symptom.
Charge Pump Pressure Becomes Low
When the engine is running, the makeup valves open and both sides of the drive loop fill with oil at charge pressure.
The charge pump is a pressure compensated piston pump. This pump provides charge oil for the steering hydraulic circuit. This pump also provides pilot supply oil for the implement valves.
Test and adjust the Charge Pressure. Refer to Specifications, Systems Operations, and Testing and Adjusting, UENR4065, "Piston Pump (Steering Charge and Pilot Pressure) - Test and Adjust".
Crossover Relief and Makeup Valves
Test and adjust the crossover relief and makeup valves. Refer to Specifications, Systems Operations, and Testing and Adjusting, UENR4065, "Piston Pump (Steering) - Test and Adjust".
Oil from the high-pressure side of the steering loop may leak across to the low-pressure side of the loop under one of the following conditions:
- The relief function or the makeup function of one of the valves is stuck open
- One of the valves springs is weak
- One of the valves springs is broken
- One of the valves springs is misadjusted
If one of the conditions listed above exists, the necessary high pressure may not be possible or may not be maintained in one or both sides of the steering loop.
Test the neutral position for the steering pump control valve. Refer to Specifications, Systems Operations, and Testing and Adjusting, UENR4065, "Piston Pump (Steering) - Test and Adjust". If the neutral position of the steering pump control valve is incorrect (off-center while in the NO STEER condition), the steering pump control valve will command the actuator piston to move off-center when there is no steering request. This condition may cause the machine to stray from straight-line travel in a NO STEER condition, and may cause the machine to steer more sharply in one direction than the other.
If the charge pump becomes too inefficient and cannot produce the required oil flow, steering will be slow to react, turns will not be as sharp, or the machine may not steer at all.
Use a flow meter in order to test the flow rate of the steering charge pump. The charge pump flow rate should be approximately
Piston Pump (Rotating Group) Flow Rate
If the piston pump becomes too inefficient and cannot produce the required oil flow, steering will be slow to react, turns will not be as sharp, or the machine may not steer at all.
Use a flow meter to test flow rate of the steering pump (flow from the rotating group). The piston pump flow rate should be approximately
Steering Pump Case Drain Flow Rate
Increased or elevated case drain flow rate indicates pump inefficiency.
If the piston pump becomes too inefficient and cannot produce the required oil flow, steering will be slow to react, turns will not be as sharp, or the machine may not steer at all.
Use a flow meter to test the flow rate of the steering pump case drain. With the flow meter in place and the engine set to 1850 RPM, case drain flow in a steering stall condition should be no more than approximately
The Pump Or The Steering Motor Has Failed
Check the case drain flow rate for the steering motor. Damage to or excessive wear of the seal around the steering motor output shaft may allow hydraulic oil (case drain) to leak past the shaft seal. Since the steering motor is installed in a bore at the top, front of the main case, hydraulic oil (from the hydraulic system) that leaks past this seal will drain directly into the main case (bevel gear case). The main case is the oil reservoir for power train oil. This condition may cause the power train oil level to increase and at the same time cause the hydraulic oil level to decrease.
Ensure that the steering motor is not worn to the point that the steering system cannot maintain the correct pressures. Wear to the steering motor rotating group may cause excessive internal (case drain) leakage. This condition may cause the steering motor to operate inefficiently. Wider (less sharp) turns, excessive noise while steering, low steering or charge pressures, and hesitation prior to turns can result.
- Start the engine and run the engine.
ENSURE THAT THE SERVICE BRAKES ARE FULLY APPLIED THROUGHOUT THIS ENTIRE PROCEDURE.
WARNING: The machine may move during this procedure if the service brakes are released or if the service brakes are weak. When you move the steering control lever during this procedure, ensure that all personnel are positioned so that no injury can occur due to machine movement.
Warm the hydraulic oil to 65°± 3°C (150°± 5°F).
- Stop the engine and disconnect hydraulic hose from the fitting on the manifold of the case drain for the steering motor.
- Place the end of the hose in a suitable container with a known volume such as a 5 gal bucket.
- Install a plug at the fitting on the case drain manifold in the same place that the line for the case drain was attached to the steering motor.
- Start the engine and set engine speed to HIGH IDLE (2200 rpm).
- Move the steering lever to the full LEFT TURN position and hold long enough to determine the case drain flow rate. Repeat this step in the full RIGHT TURN position.
The motor case drain flow rate in each direction should be approximately 4 L/min (1 gpm) in either direction.
- If the motor case drain flow rate is no more than 20% of the specification, the motor can attain the speed/pressure specifications.
- If the motor case drain flow rate is greater when steering one direction than the other, either a cross port leak (on the pressurized side) is present or the flushing valve is stuck in one position. (A cross port leak can cause the machine to drift from straight travel.)
- Replace the motor if the flow rate is more than 20% above this specification. The motor is worn and leaking too much. Retest the system after the motor is replaced.
- Check The Steering Motor Output Shaft Seal For Damage Or Wear.
Damage to or excessive wear of the seal around the steering motor output shaft can allow hydraulic oil (case drain) to leak past the shaft seal. Since the steering motor is installed in a bore at the top, front of the main case, hydraulic oil (from the hydraulic system) that leaks past this seal will drain directly into the main case (bevel gear case). The main case is the oil reservoir for power train oil. This condition will cause the power train oil level to increase and at the same time, cause the hydraulic oil level to decrease.
To determine if the shaft seal is leaking, perform the following steps:
- Remove the steering motor and wiggle the shaft to see if there is any movement.
If the shaft does not wiggle, disconnect and remove the steering motor from the machine and bench test the motor.
- Operate the motor at 425 psi in both directions. Observe the shaft seal during bench test operation and look for signs of leakage. If leakage is observed, replace the shaft seal. Carefully examine the shaft for damage where the seal and shaft contact each other. After repair and assembly, test the motor again and look for leakage at the shaft before reinstalling the motor.
If the shaft is loose, worn, or failed, bearings have allowed the shaft to cause wear to the shaft seal.
- Disassemble The Steering Motor And Inspect For Damage
If the steering motor has excessive internal wear or damage, disconnect the hydraulic lines and the electrical harness from the motor and remove the motor from the machine. Disassemble the motor and carefully examine all internal parts. Replace any worn or damaged parts as necessary and bench test, or replace the worn/damaged motor with a new motor.
- Remove the steering motor and wiggle the shaft to see if there is any movement.