120M, 12M, 140M, 140, 150, 160M and 160 Motor Graders Power Train Caterpillar

Troubleshooting the Power Train

Problem: The transmission will not shift into any gear from the Neutral position

Probable Causes

• Low Oil Level

• Low battery voltage

• Wiring harness connections

• Transmission control (shifter or forward, neutral, reverse toggle switch)

• Electrical problem with the clutch pedal

• Main relief valve

• Transmission oil pump

• Rotating seal leakage in the transmission

• Multiple ECPC valves are malfunctioning.

• The parking brake system is malfunctioning.

Problem: The transmission has lost a single gear

Probable Causes

• The wiring harness for the transmission control

• Transmission control (shifter or forward, neutral, reverse toggle switch)

• Electronic control module

Problem: The motor grader has lost multiple forward/reverse gear selections

Probable Causes

• Torsional coupling failure

• Wiring harness

• The ECPC valve is malfunctioning.

• Transmission control (shifter or forward, neutral, reverse toggle switch)

• Electronic control module

• Internal transmission problem

Note: Before performing test procedures that involve running the engine, check the magnetic screens in the transmission for bolts or metallic debris; this could indicate a torsional coupling failure.

Note: If the transmission will shift into First speed forward, Fifth speed forward, or First speed reverse, the parking brake may be engaged or there is an electrical fault in the parking brake system.

Problem: The transmission slips

Probable Causes

• Low system pressure

• Differential lock valve

• The ECPC valve requires calibration.

• The ECPC valve is malfunctioning.

• Driver in the electronic control module

• Contamination

• Rotating shaft seal

• Rotating shaft O-ring

• Worn clutch

• Mechanical problem

• The calibration of the clutch pedal

• Clutch piston seal

• The sump has low oil level.

• The pump is causing aeration.

Problem: The motor grader creeps when the clutch pedal is fully depressed

Probable Causes

• Calibration for the clutch pedal

• The ECPC valve requires calibration.

• The ECPC valve is malfunctioning.

• Wiring harness for the ECPC valve

• Wiring harness for the transmission

• Contamination

• Driver in the electronic control module

• Internal clutch drag

Problem: When the transmission shifts a hesitation occurs

Probable Causes

• The ECPC valve requires calibration.

• The ECPC valve is malfunctioning.

• Contamination in the transmission control valve

• Oil temperature sensor

• Drivers in the electronic control module

• Speed sensors

• Internal seal leakage on the transmission

• Internal pump leakage

• Main relief valve

• Differential lock valve

• Communication link between engine and transmission

• The pump is causing aeration.

Problem: The transmission shifts are harsh

Probable Causes

• Transmission speed sensor

• Wiring harness for the transmission speed sensor

• Communication link between engine and transmission

• Oil temperature sensor

• The ECPC valve requires calibration.

• The ECPC valve is malfunctioning.

• Broken spring in the main relief valve

• A spool in the main relief valve sticks.

• The piston on a clutch sticks.

Problem: The transmission shifts are sluggish

Probable Causes

• Worn clutches

• The ECPC valve requires calibration.

• The ECPC valve is malfunctioning.

• Slow clutch disengagement

• The calibration of the proportional solenoid valve

• The parking brake system is malfunctioning.

Problem: The transmission shifts at the wrong point when the autoshift control is in the ON position

Probable Causes

• Transmission intermediate speed sensor

• Transmission input speed sensor

• Transmission output speed sensor

• The electronic control module has the wrong transmission configuration code.

Problem: The transmission does not shift into all the gears when the autoshift is in the ON position

Probable Causes

• Transmission intermediate speed sensor

• Transmission input speed sensor

• Transmission output speed sensor

• The top gear limit is set.

• The operator override is selected.

Problem: The transmission shifts into the wrong gear when the autoshift is in the ON position

Probable Causes

• Transmission intermediate speed sensor

• Transmission input speed sensor

• Transmission output speed sensor

• The wiring harness for the ECPC valve is bad.

• The wiring harness for the transmission ECM is bad.

Troubleshooting the Parking Brake System

Problem: The parking brake does not hold the machine stationary.

Probable Causes

• The brake linings for the parking brake are worn.

• There is grease or oil on the brake lining.

• The parking brake must be adjusted.

Problem: The parking brake does not engage when the parking brake switch is actuated.

Probable Causes

• The parking brake switch is faulty.

• The parking brake solenoid is not operating properly.

• The main relief valve setting for the transmission is incorrect.

• The piston seals are damaged or broken.