SKM Motor Vehicle Mechanic Level 3 cheat sheet

OSHA general industry permissible exposure limit (PEL) for carbon monoxide is 50 ppm as an 8-hour time-weighted average; the short-term exposure limit is 200 ppm for a 5-minute maximum in any 2-hour period.

Abrasive blasting and spray painting with isocyanate paints require supplied-air respirators; dust and mist filtering facepieces are insufficient for isocyanates.

Compressed gas cylinders must be secured upright, stored with valve protection caps fitted, and separated so oxygen and fuel gas are at least 20 ft apart or divided by a 5 ft high fire-rated barrier.

Flash point below 60 C (140 F) classifies a liquid as flammable; flammable liquids are stored in approved safety cans or cabinets with a maximum 60 gal per cabinet.

Used oil, spent solvents, and lead-acid batteries are regulated wastes: keep manifests, label containers with accumulation start date, and never pour to storm drains.

Refrigerant recovery is mandatory under Section 608; venting CFC, HCFC, or HFC refrigerant to atmosphere is prohibited, and technicians handling refrigerant must hold EPA Section 609 certification for MVAC.

Lockout/tagout requires a personal lock and tag per worker, verification of zero energy by test, and removal only by the person who applied it.

Forklift and vehicle lift operations: rated capacity must never be exceeded, and a vehicle on a two-post lift needs the center of gravity between the posts with arms locked.

Torque wrench accuracy is typically plus or minus 4 percent of indicated value; store at the lowest scale setting and recalibrate annually or after a drop.

Micrometer reading = (barrel reading) + (thimble reading x 0.01 mm) for a metric 0.01 mm thimble; a 0.5 mm sleeve mark must be added when visible.

Vernier caliper resolution equals main scale division divided by number of vernier divisions, e.g., 1 mm / 20 divisions = 0.05 mm.

Bolt grade markings: metric property class 8.8, 10.9, and 12.9 give proof strengths roughly 580, 830, and 970 MPa; never substitute a lower class in suspension or brake joints.

Feeler gauge use requires the blade to drag slightly; a blade that enters freely or will not enter at all means the gap is outside tolerance.

Dial indicator magnetic base must be set so plunger travel is perpendicular to the measured surface; cosine error grows with the angle between plunger and surface normal.

Thread pitch is measured with a pitch gauge or by counting threads over a known length; metric fasteners are identified by diameter x pitch, e.g., M10 x 1.25.

Stoichiometric air-fuel ratio is about 14.7:1 for gasoline; lambda 1.00 means the measured ratio matches stoichiometry regardless of fuel blend.

Compression test: throttle wide open, all plugs removed, engine at operating temperature; a cylinder more than 10 percent below the highest cylinder is suspect, and a wet test rise indicates worn rings.

Cylinder leakage test: rotate each cylinder to TDC compression and apply regulated air; leakage past the intake, exhaust, or crankcase localizes the fault to valve or ring sealing.

Fuel trim: positive long-term trim above roughly plus 10 percent indicates a lean condition (vacuum leak, low fuel pressure, dirty MAF); negative trim indicates rich.

Timing belt replacement intervals are typically 60,000 to 105,000 miles or 5 to 7 years; interference engines suffer valve damage if the belt fails.

Engine vacuum at idle should be steady at 17 to 22 in-Hg at sea level; a fluctuating needle indicates a vacuum leak, valve problem, or exhaust restriction.

Coolant boiling point rises about 0.5 C per 1 psi of cap pressure; a 15 psi cap raises boiling point roughly 45 C above the unpressurized value.

Clutch pedal free play is typically 10 to 25 mm; excessive free play prevents full disengagement, and zero free play causes release bearing wear and slipping.

Automatic transmission fluid level is checked with the engine running, transmission in Park or Neutral per manufacturer, at operating temperature, on a level surface.

CV joint diagnosis: a clicking noise on turns indicates outer joint wear; vibration under acceleration indicates inner joint or axle imbalance.

Manual transmission synchronizer wear shows as gear clash when shifting; check clutch release and lubricant specification before condemning the gearbox.

Differential backlash is measured with a dial indicator on the ring gear tooth; typical specification is 0.13 to 0.20 mm, adjusted by shims.

Torque converter stall test: hold brakes, apply throttle briefly in Drive; low stall speed suggests engine power loss or converter stator fault, high stall suggests slipping clutch packs.

Driveshaft phasing requires universal joint yokes at each end to be in the same plane to avoid vibration.

Brake fluid DOT 3 and DOT 4 are glycol-based and hygroscopic; DOT 5 is silicone-based and must never be mixed with glycol fluid. Wet boiling point drops as moisture is absorbed.

Minimum brake pad friction material thickness is commonly 2 to 3 mm; brake disc minimum thickness is stamped on the hub and must not be machined below it.

Wheel alignment: camber is vertical tilt, toe is the difference in distance between front and rear of the tires, and caster is the steering axis tilt affecting straight-line stability.

Runout limits: lateral disc runout typically 0.05 mm or less; excessive runout causes pedal pulsation and requires disc replacement or resurfacing within limits.

ABS diagnosis starts with a scan tool for wheel speed sensor codes; a sensor air gap and tone ring condition must be checked before replacing the module.

Suspension bounce test: more than one rebound after pushing down a corner suggests worn dampers; also inspect for leaks and worn strut mounts.

Tire placard pressure is cold inflation; pressure rises about 1 psi per 10 F of temperature increase, so hot readings should not be used for adjustment.

Ohm's law: V = I x R; power P = V x I. A 12 V circuit drawing 5 A has 2.4 ohms resistance and dissipates 60 W.

Battery open-circuit voltage indicates state of charge: about 12.6 V is 100 percent, 12.4 V about 75 percent, 12.2 V about 50 percent, and 12.0 V about 25 percent.

Parasitic draw testing uses a clamp meter or an ammeter in series after modules sleep; typical acceptable draw is under 50 mA.

Voltage drop testing is done under load with the circuit operating; more than 0.5 V drop on a ground or power feed indicates excessive resistance.

CAN bus diagnosis: measure resistance between CAN high and CAN low with power off; about 60 ohms indicates two 120-ohm terminators intact, 120 ohms indicates an open terminator or bus break.

Alternator charging voltage is typically 13.5 to 14.8 V at idle with loads off; low output at idle but normal at speed suggests a worn belt or diode fault.

Starter current draw: a healthy starter draws roughly 150 to 250 A; excessive draw with slow cranking suggests a seized bearing or high circuit resistance.

Refrigerant identification must be confirmed with an identifier before recovery; R-12 and R-134a systems use different service fittings and oils and are never interchangeable.

R-134a uses PAG oil; R-12 used mineral oil. Mixing oils or refrigerants causes compressor failure and system contamination.

System pressures: low side typically 25 to 45 psi and high side roughly 2.2 to 2.8 times ambient temperature in C plus 100 psi on a properly charged system.

Superheat and subcooling: low superheat suggests overcharge, high superheat suggests undercharge; subcooling at the condenser outlet confirms charge on an expansion valve system.

Recovery must achieve at least 80 percent removal of refrigerant per EPA requirements before component service; evacuated systems must be leak-tested and evacuated before recharge.

A/C leak detection uses UV dye, electronic sniffers, or nitrogen pressure testing; never use compressed air or oxygen in a refrigerant system.

Cabin air filters and blower resistor diagnosis: a blower working only on high speed usually indicates an open blower resistor or module.

Pre-delivery and post-repair road tests should cover braking, steering, and speedometer function; document the test route and observations on the job card.

Four-gas exhaust analysis: high HC indicates misfire or unburned fuel, high CO indicates rich mixture, and high CO2 with low O2 indicates efficient combustion.

OBD-II readiness monitors must be complete before an emissions test; clearing codes resets monitors and may require a drive cycle to set them.

Quality control requires a second-person check on safety-critical fasteners and a torque-marker or paint mark on suspension and brake fasteners.

Brake performance test: a vehicle should stop in a straight line without pull; a pull indicates a dragging caliper, collapsed hose, or uneven friction.

Measurement records should include tool used, specification, and measured value; out-of-tolerance results require documented corrective action.

Tire tread depth minimum is 1.6 mm in most jurisdictions; measure in three grooves around the circumference and record the lowest value.

A repair order must record customer complaint, cause, correction, parts used, labor time, and technician identification; the three Cs (complaint, cause, correction) are the standard documentation format.

Written estimates require customer authorization before work begins; additional findings need a supplementary authorization recorded with date and time.

Warranty documentation must state the failure mode and the diagnostic steps taken; parts retained for warranty inspection must be tagged with the repair order number.

Communicate technical findings in plain language: state the symptom, the verified cause, the recommended repair, and the consequence of deferring it.

Customer data and vehicle access are confidential; share service history only with the vehicle owner or an authorized representative.

Follow-up communication after a major repair should confirm the symptom is resolved and record customer feedback on the job file.

A job briefing before each task should cover hazards, required PPE, tools, and the sequence of work; document attendance for high-risk tasks.

Competency assessment uses observed performance against a checklist of task steps and tolerances, not self-report alone.

On-the-job training follows a four-step method: prepare the learner, present the task, have the learner practice, and follow up with evaluation.

Delegation requires matching task authority to demonstrated competence; safety-critical tasks such as brake and steering repairs need verified sign-off.

Incident investigation records the sequence of events, root cause, and corrective action; near misses are recorded and reviewed with the team.

Workplace housekeeping and tool control reduce lost-time incidents; a shadow board or tool inventory check confirms nothing is left in a vehicle or engine bay.

Hazard communication requires a safety data sheet for every chemical in the shop and labels on all secondary containers.

Eye and face protection is required during grinding, cutting, and battery service; face shields supplement but do not replace safety glasses.

Battery charging releases hydrogen; keep ignition sources away and ventilate the area to stay below the lower explosive limit.

Spill response: absorbent material and a spill kit must be available near fuel and oil storage; reportable releases follow the local environmental authority's threshold.

Hand and arm vibration exposure from impact tools should be limited; use low-vibration tools and anti-vibration gloves for extended use.

Hydraulic press and puller use requires the workpiece to be centered and supported; never stand in line with the press ram.

Bench grinder safety: the tool rest gap should not exceed 2 mm and the tongue guard gap about 6 mm; ring-test wheels before mounting.

Torque-to-yield bolts must be replaced, not reused, because they stretch permanently past the elastic limit.

Precision measuring tools should be checked against a known standard before use; a micrometer zero check uses the anvil faces closed on the standard.

Air tool pressure should match the tool rating, typically 90 psi at the tool inlet; excessive pressure accelerates wear and increases hazard.

Valve clearance is measured cold or hot per specification; incorrect clearance causes noise, poor sealing, or valve damage.

Head bolt torque sequence starts at the center and spirals outward in stages; torque-to-yield bolts are tightened by angle after reaching the torque value.

Oil pressure specification is typically 1 bar at idle and 3 to 4 bar at speed; low pressure may indicate worn bearings, a faulty relief valve, or a clogged pickup.

Turbocharger diagnosis: excessive shaft play, oil in the intake, or a whining noise indicates bearing wear; verify oil supply and return before replacement.

EGR and PCV faults cause rough idle and oil consumption; a stuck-open EGR valve produces a lean misfire at idle.

Automatic transmission line pressure testing identifies hydraulic faults; low pressure in all ranges suggests a pump or pressure regulator fault.

Shift solenoid and valve body faults produce harsh or delayed shifts; a scan tool can command each solenoid to verify operation.

Clutch hydraulic system bleeding removes air that causes a spongy pedal and incomplete release.

Constant velocity boot inspection: a torn boot allows grease loss and dirt ingress, leading to joint failure; replace the boot before the joint fails.

Final drive ratio equals ring gear teeth divided by pinion teeth; it determines engine speed relative to road speed.

Brake bleeding sequence typically starts at the wheel farthest from the master cylinder; ABS systems may require a scan tool bleed procedure.

Parking brake adjustment should allow a specified number of clicks; excessive travel indicates worn shoes or a stretched cable.

Steering free play is measured at the steering wheel rim; more than about 25 mm indicates worn tie rods, a steering box, or a column joint.

Wheel bearing diagnosis: a growling noise that changes with steering load indicates a worn hub bearing; check for play and roughness.

Shock absorber and strut replacement should be done in axle pairs to preserve handling balance.

A relay coil draws a small current; a relay that clicks but does not pass power has burned contacts and should be replaced.

Fuse rating must match the circuit; a fuse that repeatedly blows indicates a short or an overloaded circuit, not a fuse problem.

Multimeter usage: voltage measured in parallel, current in series, resistance with the circuit de-energized.

Ground circuit testing: measure voltage between the component ground and battery negative while the load is on; more than 0.2 V indicates a poor ground.

Immobilizer and key programming require a scan tool with security access; record the programming event in the job file.

Compressor clutch does not engage: check refrigerant pressure switch, clutch coil resistance, and the control module command before replacing the compressor.

Condenser airflow restriction raises high-side pressure; clean the condenser fins and confirm the cooling fan operates at the correct speed.

Expansion valve and orifice tube faults: a stuck-closed valve gives low suction pressure, and a stuck-open valve gives high suction pressure with poor cooling.

Evacuation should hold vacuum for at least 10 to 15 minutes; a vacuum that rises indicates a leak.

Refrigerant charge must be weighed in per specification; overcharge reduces cooling and raises high-side pressure.

Brake fluid moisture testing uses a tester that reads percentage water; above about 3 percent requires fluid replacement.

Battery load test: apply half the cold cranking amp rating for 15 seconds; voltage should stay above 9.6 V at 20 C.

Cooling system pressure test: pressurize to cap rating and hold; a falling gauge indicates a leak, and a rising gauge with the engine running may indicate a head gasket fault.

Road test after wheel alignment should confirm a centered steering wheel and no pull.

Final inspection checklist should include fluid levels, torque marks, tool inventory, and a clean vehicle interior.

A declined repair should be documented with the customer's decision and the date, protecting both parties if a related failure occurs later.

Labor time should be recorded against the operation performed; flat-rate and actual time should be reconciled for warranty claims.

Parts return and core documentation must reference the repair order; core credits depend on returning the old component.

Explain technical terms with analogies and avoid jargon; confirm customer understanding by asking them to restate the plan.

Complaint handling: acknowledge the concern, gather facts, state the resolution options, and record the agreed outcome.

Training records should list the task, the trainer, the date, and the assessment result, and be retained for audit.

A toolbox talk should be short, topic-specific, and tied to a recent incident or near miss in the shop.

Performance feedback should reference observable behavior and measured outcomes rather than personality.

Work allocation must respect the legal limits on apprentice supervision for safety-critical repairs.

A supervisor should verify that personal protective equipment is worn and that guards are in place before work starts.

Noise exposure above 85 dBA as an 8-hour average requires a hearing conservation program with audiometric testing and hearing protection.

Confined space entry into fuel tanks or pits requires atmospheric testing for oxygen, flammables, and toxics before entry.

Waste segregation: chlorinated solvents, waste oil, and aqueous parts-washer fluid are separate waste streams with separate containers.

Emergency eyewash and shower stations must be within 10 seconds' travel of corrosive chemical handling areas.

Vehicle exhaust must be vented to outdoors during engine running in an enclosed shop to keep CO below the PEL.

Lift point location must follow the manufacturer's diagram; lifting at the wrong point can crush floor pans or damage fuel and brake lines.

Jack stands must be rated for the load and placed on a hard level surface; a hydraulic jack alone is not a support.

Impact sockets are made of softer, thicker material than chrome hand sockets; using a chrome socket on an impact wrench can shatter it.

Torque angle gauges are used for torque-to-yield fasteners after the initial torque value is reached.

A tap and die set is matched to thread diameter and pitch; using the wrong pitch damages the thread.

Cooling system air pockets cause overheating; bleed the system at the highest point and run the heater to purge air.

Thermostat opening temperature is stamped on the part; a thermostat stuck open causes slow warm-up and poor heater output.

Fuel injector balance testing compares pressure drop across injectors; a low drop indicates a clogged or faulty injector.

Knock sensor faults cause retarded timing and reduced power; check the sensor mounting torque and wiring shield.

Serpentine belt routing must follow the underhood diagram; a misrouted belt can turn the water pump backward.

Transmission fluid color is not a reliable diagnosis alone; burned smell and clutch material in the pan indicate internal wear.

A torque converter that drains back overnight causes a delayed engagement; check the anti-drainback valve and fluid level.

Driveline vibration diagnosis: vibration that changes with vehicle speed points to the driveshaft or wheels; vibration that changes with engine speed points to the engine or converter.

Limited-slip differentials require friction modifier additive; omitting it causes chatter on turns.

Shift linkage adjustment should be verified in all ranges, including Park, before returning the vehicle.

Brake hose inspection: cracks, bulges, or a hose that holds pressure after release indicate internal collapse and require replacement.

Proportioning valve and load-sensing valve faults cause rear wheel lockup; verify rear brake pressure under load.

Tie rod end play is checked by rocking the wheel while an assistant holds the steering wheel; any visible play requires replacement.

Strut mount bearing noise is a popping sound when turning the steering wheel at low speed.

Tire wear patterns: inner or outer edge wear indicates camber or toe error; cupping indicates worn dampers or imbalance.

Wiring repair should use crimped and sealed connectors or solder with heat shrink; twisted wires and tape are not acceptable for a permanent repair.

Sensor reference voltage is typically 5 V; a shorted reference pulls down multiple sensors on the same circuit.

Actuator testing with a scan tool confirms the control module command and the circuit path.

Battery terminal corrosion increases resistance; clean and apply protective coating, then verify charging voltage.

LED and HID lighting conversions must meet the vehicle's lighting regulations and not blind oncoming traffic.

Blend door actuator faults cause temperature control problems; a scan tool can command the door and confirm feedback position.

Refrigerant oil must be replenished by the amount removed with the recovered refrigerant; overfilling reduces cooling.

Receiver-drier replacement is required whenever the system is opened to atmosphere for an extended period.

High-side pressure that rises quickly with low cooling may indicate a restricted condenser or an overcharged system.

Cabin temperature sensor and sunload sensor inputs affect automatic climate control; check sensor values before replacing the control head.

A pre-work inspection should record existing damage and fluid levels with the customer present where possible.

Wheel alignment printouts should show before and after values for camber, caster, and toe on all four wheels.

Diagnostic scan tool freeze-frame data should be recorded with the fault code to support the diagnosis.

A repair is not complete until the original complaint is verified as resolved by a road test or functional test.

Calibration records for torque wrenches, lifts, and diagnostic equipment support quality audits.

A written estimate should separate parts, labor, and tax and state the validity period.

Customer authorization by phone should be documented with the name of the person authorizing and the time.

Job documentation should be legible, use standard abbreviations, and avoid ambiguous terms such as 'fixed' without a described action.

Follow up on deferred work at the next service visit and record the recommendation again.

Data protection requires secure storage of customer records and controlled access to the workshop management system.

A skills matrix maps each technician to tasks and competence levels; it is used to plan training and allocate work.

Instruction should state the standard, demonstrate it, and then observe the learner performing it to the standard.

Safety induction for new staff covers emergency exits, first aid, fire equipment, and chemical handling.

Supervisors should audit completed jobs against the checklist and provide corrective feedback promptly.

Team briefings should review near misses and confirm that corrective actions from incidents have been implemented.