PM Class C Full Preventive Maintenance Checklist for Freightliner Highway Trucks

PM Class C Service Information

PM Class C is a comprehensive preventive maintenance service typically performed every 30,000-40,000 miles (48,000-64,000 km) or according to manufacturer specifications. This maintenance includes all items from Class A and B services plus additional in-depth inspections, fluid changes, and component servicing. This checklist is specifically designed for Freightliner highway truck models including Cascadia, Coronado, Classic, Century, and Columbia equipped with Detroit diesel engines. Following this PM Class C service schedule helps maximize vehicle uptime, extend component life, and ensure compliance with manufacturer warranty requirements.

Required Service Items

The following items must be replaced or serviced during a PM Class C maintenance service.

Engine Service Requirements

Change engine oil and filter(s)
Replace fuel filter(s) - primary and secondary
Replace coolant filter (if equipped)
Test coolant freeze protection and SCA level
Check/adjust valve lash (per Detroit specifications)
Inspect/replace crankcase ventilation filter
Clean/replace EGR cooler (as needed)

Drivetrain Service Requirements

Change transmission fluid and filter (DT12/manual)
Change drive axle lubricant
Service wheel bearings (clean and repack)
Change transfer case fluid (if equipped)
Lubricate universal joints and driveshaft splines
Check/adjust clutch free play (manual transmissions)
Inspect transmission mounts and isolators

Air System Service

Replace air dryer desiccant cartridge
Replace air filter element
Clean/replace air compressor inlet filter
Drain and inspect air tanks for contamination
Test air governor cut-in and cut-out pressure
Measure air compressor build time (0-120 PSI)
Test air dryer purge function

Emissions System Service

Clean/inspect DPF filter (per dash indicator)
Check/clean DEF tank strainer
Test DEF quality with refractometer
Inspect/clean NOx sensors
Check exhaust system for leaks or damage
Inspect SCR catalyst for damage
Perform DPF regen check and system test

Detroit Engine System Inspection

Comprehensive inspection of Detroit diesel engine components specific to Freightliner trucks.

Engine Mechanical Inspection

Perform cylinder compression test
Check engine mounts for damage or deterioration
Inspect fan hub and bearing for play
Check crankshaft endplay and thrust bearing wear
Inspect vibration damper for fluid leaks or wobble
Check turbocharger for shaft play or oil leaks
Inspect engine block heater function (if equipped)
Check EGR valve operation and carbon buildup

Engine Belt Drive System

Inspect/replace serpentine belt
Check automatic belt tensioner function
Inspect all belt-driven accessory pulleys
Verify belt alignment on all pulleys
Check for belt glazing or contamination
Inspect fan clutch for proper engagement
Test fan override switch function
Inspect belt guards and shrouds for damage

Cooling System Inspection

Pressure test cooling system (15 PSI minimum)
Inspect radiator for internal/external corrosion
Check radiator cap pressure relief function
Inspect water pump for bearing play and leakage
Check thermostat operation and opening temperature
Inspect all coolant hoses for deterioration
Verify coolant level sensor operation
Test radiator fan clutch temperature response

Fuel System Inspection

Check fuel pump pressure and volume
Inspect fuel tank for damage or contamination
Check for fuel leaks at all connection points
Test fuel water separator efficiency
Inspect electronic fuel injectors for leaks
Check high pressure fuel pump operation
Verify fuel filter restriction indicator
Test fuel level sensor accuracy

Air Intake System

Test intake restriction indicator function
Inspect charge air cooler for leaks or damage
Check turbocharger boost pressure
Inspect intake manifold for cracks or leaks
Check all intake hoses and clamps
Verify intake air temperature sensor
Inspect air filter housing seal integrity
Check air-to-air connections for leaks

Engine Electronic Systems

Connect DDDL/DiagnosticLink for fault code check
Verify all sensor inputs are within specifications
Check engine harness for chafing or damage
Test ECM power and ground integrity
Verify engine protection shutdown functions
Check cruise control operation
Update ECM software to latest version
Verify parameter settings match vehicle specs

Lubrication System

Check oil pressure at idle and rated RPM
Inspect oil cooler for leaks or restrictions
Verify oil pressure sensor accuracy
Check oil filter base for cracks or leaks
Inspect PCV system function
Check oil pan for damage or leaks
Verify oil level sensor operation
Inspect oil pump pickup screen for debris

Engine Wiring & Sensors

Check crankshaft position sensor mounting
Verify camshaft position sensor operation
Test coolant temperature sensor accuracy
Check oil pressure sensor function
Inspect all engine wiring harness connectors
Verify fuel pressure sensor reading
Test intake air temperature sensor
Check exhaust temperature sensors

Drivetrain & Chassis Inspection

Comprehensive inspection of Freightliner drivetrain and chassis components.

DT12 Automated Transmission

Check transmission ECU for fault codes
Inspect shift actuator operation
Test clutch actuator pressure
Check transmission oil cooler for leaks
Verify shift pattern and gear engagement
Inspect transmission mounts for deterioration
Check PTO operation (if equipped)
Verify transmission range sensors

Manual Transmission Inspection

Verify clutch free play and adjustment
Check clutch brake function (if equipped)
Inspect clutch linkage or hydraulic system
Verify shifter operation in all gears
Check for transmission oil leaks
Inspect transmission input shaft seal
Check PTO (if equipped) for leaks or noise
Verify speedometer drive function

Drive Axle Inspection

Check differential oil level and condition
Inspect axle breather for blockage
Verify differential lock function (if equipped)
Check pinion seal for leakage
Inspect axle housing for cracks or damage
Check inter-axle driveline (tandem axles)
Verify ABS sensor mounting and air gap
Check axle vent for proper operation

Driveline Components

Inspect universal joints for wear
Check driveshaft carrier bearing (if equipped)
Verify driveshaft slip joint lubrication
Inspect driveshaft tube for damage or dents
Check driveline angles for proper alignment
Verify driveshaft balance and vibration
Inspect driveline guards (if equipped)
Check for loose or missing hardware

Steering System

Check steering gear box mounting
Inspect steering shaft and U-joints
Verify power steering pump pressure
Check power steering fluid condition
Inspect drag link and tie rod ends
Check steering damper operation
Verify steering stops are properly adjusted
Test steering wheel return to center

Suspension System

Inspect air bags for damage or leaks
Check air suspension height control valves
Verify shock absorber operation
Inspect torque rods and bushings
Check suspension mounting brackets
Verify leaf spring condition and alignment
Inspect frame rails for cracks or damage
Check air system dump valve operation

Wheel End Components

Inspect wheel bearings for wear or damage
Check wheel seals for leakage
Verify hub cap condition and venting
Inspect wheel studs and nuts for damage
Check wheel bearing adjustment
Verify hub oil level (oil lubricated hubs)
Inspect ABS sensors and wiring
Check for wheel end temperature issues

Fifth Wheel & Coupling System

Inspect fifth wheel top plate for wear
Check fifth wheel jaws and locking mechanism
Verify fifth wheel mounting bolts torque
Inspect sliding fifth wheel mechanism
Check slider locking pins for wear
Verify proper fifth wheel lubrication
Inspect air release system (if equipped)
Check secondary locking mechanism

Electrical & Safety Systems

Detailed inspection of electrical and safety systems specific to Freightliner trucks.

Battery & Charging System

Load test all batteries
Check battery electrolyte level (if applicable)
Clean and protect battery terminals
Verify battery box integrity and mounting
Test alternator output under load
Check alternator mounting and belt alignment
Verify battery disconnect switch function
Test charging system voltage regulation

Starting System

Measure starter current draw
Check starter mounting and security
Inspect starter solenoid function
Verify starter relay operation
Test neutral safety switch function
Inspect starter cables for damage
Check starter nose for alignment with flywheel
Verify cranking speed is adequate

Lighting & Instrumentation

Verify all exterior lighting operation
Check all dash gauges and indicators
Test low air pressure warning system
Verify ABS/stability control indicators
Check all indicator light brightness
Test dash illumination control
Verify horn operation (air and electric)
Check windshield wiper and washer function

Detroit Assurance System

Check radar sensor alignment and cleaning
Verify camera calibration and operation
Test active brake assist system
Check adaptive cruise control function
Verify lane departure warning system
Test headway alert function
Check Detroit Assurance ECU for fault codes
Verify system warning indicators

Chassis Electrical

Inspect main electrical harnesses for damage
Check all junction boxes and connections
Verify ground strap integrity
Test trailer electrical connection
Check body builder connections
Verify ABS/ESP harness connections
Inspect VECU (Vehicle Electronic Control Unit)
Check all circuit protection devices

HVAC System

Test air conditioning performance
Check heater output temperature
Verify HVAC control function
Inspect A/C compressor operation
Check coolant flow through heater core
Test defroster performance
Check cabin air filter condition
Verify blower motor operation at all speeds

Air Brake System

Verify brake chamber pushrod travel
Check slack adjuster function and angle
Test spring brake operation
Inspect brake drums/rotors for wear
Check brake lining condition and thickness
Verify ABS modulator valve function
Test air governor operation and settings
Check all air system pressure protection valves

Interior & Ergonomics

Check driver's seat mounting and adjustment
Verify seat belt function and condition
Test all door latches and window regulators
Check interior lights and dimmer function
Verify all dash switches and controls
Inspect steering wheel tilt/telescope function
Check sun visor operation
Verify all optional comfort accessories

Diagnostic & Software Updates

Complete these diagnostic procedures and software updates as part of PM Class C service.

Electronic Control Module Testing

Connect Detroit DDDL/DiagnosticLink software
Download and document all active/inactive fault codes
Verify ECM parameter settings match vehicle spec
Check for available software updates
Test all sensor inputs against specification
Verify component protection settings
Document performance data during test drive
Verify Virtual Technician system connectivity

Software Update Procedures

Update engine control module software
Update transmission control module software
Update aftertreatment control module
Update Detroit Assurance system
Verify all module versions are compatible
Document all software version changes
Verify proper system function after updates
Ensure all customer-specific parameters are retained

Functional Testing

Perform engine performance road test
Verify transmission shift pattern and timing
Test hill-holding function (DT12 transmission)
Verify engine brake operation (all stages)
Test cruise control and adaptive cruise
Verify Auto-shift and Skip-shift functions
Check throttle response and progressive shifting
Verify PPC (Predictive Powertrain Control) operation

Documentation Requirements

Complete all PM service documentation
Document all fault codes found/cleared
Record all fluid quantities and specifications used
Document all parts replaced with part numbers
Update maintenance tracking system
Create maintenance sticker for windshield
Document technician performing service
Schedule next PM service interval

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