MITO Light Auto L5 cheat sheet

Vehicle categories by EU framework: M = passenger transport (M1 up to 8 seats plus driver), N = goods (N1 gross mass ≤3.5 t), L = two/three-wheelers, O = trailers; MITO Light Auto scope centers on M1 and N1.

Gross vehicle mass (GVM) = kerb mass + payload + driver allowance; gross train mass (GTM) = GVM + towed trailer mass, limited by the lowest-rated component (hitch, towbar D-value, or drivetrain).

Kerb mass includes all fluids, tools, and 90% fuel; payload = GVM − kerb mass and must never be exceeded by axle loads, not just total mass.

Axle load distribution rule: front and rear axle ratings are independent limits; a legal total mass can still overload one axle if load is poorly distributed.

Chassis construction types: ladder-frame (body-on-frame, high torsional stiffness, typical of light trucks), unitary/monocoque (mass-efficient, crash-load paths through sills and pillars), and spaceframe.

Drive layouts: FF (transverse engine, compact, understeer-biased), FR (longitudinal, balanced, propshaft tunnel), AWD/4WD (transfer case or on-demand coupling).

Light vehicle classification by fuel/energy: ICE (petrol, diesel), HEV (series, parallel, power-split), PHEV, BEV, FCEV; each carries distinct inspection items (e.g., HV cables, hydrogen tanks).

Four-stroke cycle order: intake → compression → power (expansion) → exhaust; two crankshaft revolutions per cycle, one power stroke per cylinder per 720° of crank rotation.

Displacement = π/4 × bore² × stroke × number of cylinders; compression ratio = (swept volume + clearance volume) ÷ clearance volume.

Volumetric efficiency = actual intake air mass ÷ theoretical (displacement-derived) air mass; naturally aspirated ~80–90%, boosted engines exceed 100% relative to displacement.

Air-fuel ratio: stoichiometric petrol ≈ 14.7:1 by mass, diesel ≈ 14.5:1; lambda = actual AFR ÷ stoichiometric AFR, with lambda = 1 at stoichiometry.

Torque and power relation: P (kW) = T (N·m) × n (rpm) ÷ 9549; peak torque and peak power occur at different engine speeds.

Diesel combustion is compression-ignition (injection near TDC, ~17–22:1 CR); petrol is spark-ignition with knock limited by octane rating and ignition timing.

Transmission ratio and road speed: v = (n × 2πr) ÷ (60 × overall gear ratio), where r = tyre rolling radius; final drive ratio multiplies gearbox ratio.

Common rail diesel: high-pressure pump feeds a rail, ECU commands solenoid/piezo injectors for pilot, main, and post injections to reduce noise and emissions.

Ohm's law V = I × R; power P = V × I = I²R = V²/R; series resistances add, parallel resistances follow 1/R_total = Σ(1/Rn).

12 V nominal lead-acid battery: open-circuit voltage ≈ 12.6 V at full charge, ≈ 12.0 V at 50% state of charge; charging voltage from alternator typically 13.8–14.4 V.

Starter circuit voltage drop test: measure from battery positive to starter terminal and from starter body to battery negative while cranking; total drop above ~0.5 V indicates excessive resistance.

Alternator output test: measured voltage should rise to charging range with engine running; a diode failure shows as AC ripple, checked with a multimeter set to AC volts.

CAN bus: differential pair CAN-H/CAN-L, nominal 60 Ω termination (two 120 Ω resistors), recessive ≈ 2.5 V both lines, dominant ≈ 3.5 V / 1.5 V; a shorted or open bus disables communication.

High-voltage safety threshold: systems above 60 V DC or 30 V AC are classified hazardous; technicians require HV qualification, insulated tools, and verified de-energization before work.

Sensor and actuator basics: NTC coolant sensor resistance falls as temperature rises; MAP/MAF measure load; lambda sensor output switches around 0.45 V for narrowband zirconia types.

Wheel alignment angles: camber (vertical tilt), caster (steering-axis tilt, provides self-centering), toe (front/rear), and thrust angle (rear axle alignment relative to vehicle centerline).

Suspension types: MacPherson strut, double wishbone, multilink, torsion beam, and live axle; each defines camber/toe curves and adjustment points.

Tyre marking interpretation: e.g., 205/55 R16 91V = section width 205 mm, aspect ratio 55%, radial, 16-inch rim, load index 91, speed rating V.

Brake hydraulic principle: pedal force × pedal ratio × (master cylinder area ÷ caliper piston area) = clamping force; brake fluid is hygroscopic and DOT 4 has a minimum dry boiling point of 230 °C.

Disc vs drum: discs dissipate heat better and self-adjust; drums provide higher shoe self-energizing force but fade and require periodic adjustment.

ABS function: wheel-speed sensors detect lock-up, ECU modulates hydraulic pressure via solenoid valves; a wheel-speed sensor fault disables ABS and typically lights the warning lamp.

Steering geometry: Ackermann principle means inner wheel turns more than outer; excessive play in tie rods or rack indicates wear and fails inspection.

Diagnostic sequence: verify customer complaint → confirm symptom → retrieve DTCs → inspect wiring/connectors → test components → repair → clear codes and verify with road test.

OBD-II standard: 16-pin DLC, CAN pins 6 and 14; readiness monitors (misfire, fuel system, components, catalyst, EVAP, O2, EGR) must be complete before emissions testing.

DTC structure: Pxxxx (powertrain), B (body), C (chassis), U (network); first digit after letter indicates whether the code is generic or manufacturer-specific.

Service intervals: oil and filter per manufacturer schedule (typically 10,000–20,000 km or 12 months); brake fluid every 2 years; timing belt per OEM interval or mileage, whichever first.

Tyre tread minimum legal depth 1.6 mm (EU), recommended replacement at 3 mm; measure at three points across the tread and check for uneven wear indicating alignment faults.

Torque specification rule: always use a calibrated torque wrench, tighten in stages and in a cross pattern for multi-bolt joints; never reuse torque-to-yield bolts.

Pre-delivery and periodic inspection covers fluid levels, belt condition, brake pad thickness, suspension play, lighting, and battery state of charge.

Personal protective equipment: safety glasses, gloves, hearing protection above 85 dB(A), and steel-toe boots are mandatory in the workshop.

Lifting rule: use rated jacks and stands on a level surface; never work under a vehicle supported only by a hydraulic jack; chock wheels and follow lift-point diagrams.

Fuel and solvent storage: flammable liquids in approved containers, away from ignition sources; spill kits and eyewash stations must be accessible.

Exhaust emissions control: three-way catalyst reduces CO, HC, and NOx at stoichiometric operation; diesel uses DOC, DPF, and SCR with AdBlue (urea) for NOx reduction.

Waste handling: used oil, filters, coolant, and batteries are hazardous waste requiring licensed collection; never pour into drains or soil.

Refrigerant handling: R-1234yf and R-134a require recovery equipment; venting to atmosphere is prohibited; technician certification is required for A/C service.

High-voltage and battery safety: isolate HV systems per OEM procedure, verify zero energy, use insulated gloves rated for the system voltage, and never assume a vehicle is de-energized without testing.