NVQ L4 Automobile Technician cheat sheet

COSHH requires a current safety data sheet for every hazardous substance on site; assessment must be reviewed when the product, task or exposure changes.

Workplace exposure limits are expressed as 8-hour time-weighted average (WEL-TWA) and 15-minute short-term (WEL-STEL); both must be controlled, not just the TWA.

Manual handling risk is assessed against the load, posture, repetition and environment; a two-person lift is required when a component exceeds the individual's safe handling capacity, not a fixed 25 kg figure.

Vehicle lifting: jacking points are defined by the manufacturer; axle stands must be rated above the supported load and placed on load-bearing chassis or subframe points, never on sills or floor pans.

Fire classification: Class A solids, Class B flammable liquids, Class C gases, Class D metals, Class F cooking oils; electrical fires require CO2 or dry powder, never water.

Battery charging releases hydrogen; the charging area requires ignition-source control and ventilation, and lead-acid electrolyte is a corrosive requiring eye protection and eyewash access.

Housekeeping: 5S (sort, set, order, standardise, sustain) is the audit framework; walkways and fire exits must remain clear, and spill kits are positioned at the point of risk, not centrally.

RIDDOR reporting thresholds include over-7-day incapacitation, specified injuries, dangerous occurrences and occupational disease; the report must be made within 10 days of the incident.

Diagnostic sequence: verify the complaint, gather symptoms, check for technical bulletins and known fixes, test systematically, confirm the repair - never replace parts on symptom alone.

DTCs are stored as confirmed, pending and permanent; a permanent code clears only after the ECU completes its self-test cycle, so erasing codes does not prove a fault is fixed.

Freeze-frame data records operating conditions at the moment of fault storage; it is the primary evidence for intermittent faults and must be captured before codes are cleared.

Voltage drop testing measures circuit loss under load: probe across the conductor or connection while current flows; more than 0.5 V on a power or ground circuit indicates excessive resistance.

Parasitic drain: measure with a current clamp or in series after all modules sleep; typical acceptable values are 20–50 mA, and a higher reading requires a timed sleep and module-by-module isolation.

Fuel trim: positive long-term trim means the ECU is adding fuel (lean condition - vacuum leak, low fuel pressure, dirty MAF); negative trim means it is removing fuel (rich condition).

OBD readiness monitors must be complete before an emissions test; clearing codes resets monitors, so a drive cycle is required to re-run them.

Root-cause discipline: a repaired symptom that recurs within the same operating conditions indicates the underlying cause was not identified; document the test evidence for each replaced component.

Cylinder head torque sequences are manufacturer-specific and typically spiral from the centre outward; torque-to-yield bolts must be replaced and tightened to angle, not reused.

Valve clearance is measured cold or hot per specification; incorrect clearance causes burnt valves (too tight) or noise and cam wear (too loose).

Compression test interpretation: a dry test followed by a wet test that rises significantly indicates worn rings; no rise indicates valves, head gasket or cam timing.

Cylinder leakage test: leakage past the intake indicates intake valve, past the exhaust indicates exhaust valve, into the crankcase indicates rings or piston, and bubbles in coolant indicate head gasket or crack.

Timing belt and chain: alignment marks must be verified at crank and cam before and after tensioning; an interference engine will suffer valve-to-piston contact if timing is lost.

Bearing clearance is checked with plastigauge or micrometers against specification; oil clearance that is too tight causes seizure, too loose causes low oil pressure and knock.

Engine oil pressure: low at idle with normal at speed suggests worn bearings or a worn pump; low across the range suggests a relief valve, pickup restriction or sender fault.

After overhaul, a running-in procedure includes correct oil, priming the oil system before first start, retorquing where specified, and a post-run leak and compression check.

CAN bus: dominant bit (0) overwrites recessive (1); the bus is a twisted pair with 120 Ω termination at each end, giving about 60 Ω measured across the pair with the network powered down.

CAN fault diagnosis: a shorted bus reads near 0 Ω, an open termination reads about 120 Ω, and a single-wire short to ground or battery is isolated by disconnecting nodes and re-measuring.

LIN bus is single-wire, master-slave, typically 9.6–20 kbit/s, and used for low-speed body functions such as mirrors, seats and sensors; a LIN node cannot communicate if the master is faulty.

FlexRay and automotive Ethernet are used for high-speed safety and camera systems; Ethernet uses point-to-point links through a switch, so a single faulty node does not necessarily disable the network.

High-voltage systems (typically 400–800 V DC) require a verified isolation test, PPE rated to 1000 V, lockout/tagout, and a waiting period per manufacturer before work; the isolation resistance minimum is manufacturer-specified.

Sensor types: inductive (passive, generates AC, no supply), Hall-effect (three-wire, digital square wave), and potentiometer (three-wire, analogue voltage divider) - the test method differs for each.

Actuator testing: PWM-controlled actuators are verified with duty-cycle measurement or current waveform, not a simple voltage check, because average voltage depends on duty.

Battery management: state of charge and state of health are separate values; a battery that accepts charge but has low state of health will fail under load despite a normal open-circuit voltage.

Brake fluid is hygroscopic; absorbed moisture lowers boiling point and causes pedal fade, so fluid is tested for water content and replaced on the manufacturer's interval.

Brake hydraulic diagnosis: a spongy pedal indicates air or a flexible hose expansion; a pedal that sinks under constant pressure indicates an internal master cylinder or ABS valve leak.

Disc thickness variation causes pulsation under braking and is measured with a micrometer at multiple points; runout is measured with a dial gauge on the hub face with the disc fitted.

Wheel alignment: toe is the primary tyre-wear angle; excessive toe causes feathered edge wear, camber causes one-sided wear, and incorrect caster affects straight-line stability and self-centring.

Suspension inspection: a failed damper shows as oil misting, excessive bounce, or cupped tyre wear; a worn bush shows as movement under load and clunk over bumps.

Steering: play is measured at the steering wheel rim against specification before suspecting the rack; a rack-end or track-rod-end fault produces play that changes with wheel position.

ABS diagnosis: wheel speed sensor air gap and tone-ring condition are checked first; a sensor signal can be verified on a scope for amplitude and consistency across wheels.

Parking brake and EPB systems require a service mode to retract the caliper; retracting without service mode can damage the motor and caliper.

Automatic transmission fluid level is checked at a specified fluid temperature with the engine running and the selector cycled; an incorrect level causes slip (low) or foaming and overheating (high).

Torque converter diagnosis: stall test compares engine speed against specification; high stall suggests a worn converter or slipping clutch pack, low stall suggests an engine or converter one-way clutch fault.

CV joint diagnosis: a clicking noise on full lock indicates an outer joint; vibration under acceleration indicates an inner joint or driveshaft imbalance.

Manual gearbox: oil is checked at the fill plug level; a whine that changes with gear indicates gear or bearing wear, and a whine in all gears suggests the input shaft bearing.

Dual-clutch and CVT systems require manufacturer-specific fluid and adaptation reset after fluid service or clutch replacement; using the wrong fluid causes judder and premature failure.

Differential: backlash and preload are set with shims and measured with a dial gauge; incorrect backlash causes whine on drive or overrun depending on which side of the gear tooth contacts.

Driveline vibration diagnosis distinguishes vehicle speed-related (wheels, propshaft balance) from engine speed-related (clutch, flywheel) by changing gear at the same road speed.

Four-wheel-drive systems: mismatched tyre circumference across axles causes wind-up and transfer case damage; tyres must be matched within the manufacturer's tolerance.

Inspection sequence: exterior and lighting, braking performance, steering and suspension, tyres and wheels, emissions and exhaust, structural corrosion, then documentation and advisories.

Brake performance is assessed against a specified efficiency figure and imbalance limit; a roller brake tester records each wheel's braking force for comparison.

Tyre inspection: legal minimum tread is 1.6 mm across the central three-quarters around the whole circumference; sidewall damage, exposed cords and incorrect load rating are rejectable.

Emissions testing: petrol engines are assessed on CO and HC at idle and raised idle plus lambda; diesel on smoke opacity, with limits depending on the test standard applied.

Corrosion assessment: a structural area within a specified distance of a suspension, steering or seat belt mounting point is rejectable if it affects strength.

Quality control uses a documented inspection and test plan with hold points; a first-off and last-off check catches process drift, and rework must be re-inspected to the same standard.

Calibration: measuring equipment must be within its calibration interval and traceable to a national standard; an out-of-calibration gauge invalidates the recorded result.

Record retention: inspection records, test results and technician identification must be retained for the period required by the scheme so a result can be audited later.

Job planning: confirm parts availability, special tooling, technical information and technician competence before the vehicle enters the bay; a job that stalls on a missing tool is a planning failure.

Critical path method identifies the longest dependent sequence; float is the slack on non-critical tasks, and reducing a critical-path task shortens the whole job.

Work allocation matches task complexity to competence level; a trainee may perform a task only under supervision appropriate to the risk and their recorded competence.

Time estimation uses standard times adjusted by vehicle condition; variance between estimated and actual time is the measure used to improve future estimates.

Delegation requires a clear outcome, authority, resources and a deadline; accountability for the result remains with the supervisor.

Tool and equipment control: special tools are logged in and out, calibrated equipment is checked before use, and missing tooling is investigated before the next job starts.

Handover communication uses a written record of work completed, work outstanding, parts fitted and safety-critical findings; verbal-only handover loses traceability.

Performance monitoring uses measurable indicators such as rework rate, comeback rate, on-time completion and utilisation; these are reviewed against targets, not impressions.

Complaint handling sequence: listen without interruption, acknowledge the concern, establish the facts, agree the remedy, confirm in writing, and follow up.

Technical explanation to a customer should state the fault, the evidence, the options and the cost consequence, in plain language without jargon or acronyms.

Estimates must distinguish between a quotation (fixed price) and an estimate (subject to change); any additional work requires fresh authorisation before it is carried out.

Consent and data: customer contact details, vehicle data and diagnostic records are personal data and must be stored and shared only for the agreed purpose.

Authorisation record: who authorised the work, what was authorised, the price and the date must be documented, because it is the evidence in a dispute over charges.

Managing expectations: give a realistic completion time that includes parts lead time and unforeseen findings, and notify the customer as soon as the expectation changes.

Vulnerable customers and safety-critical faults: where a vehicle is unroadworthy, the customer must be told clearly in writing that it should not be driven.

Feedback and comeback analysis: a returned vehicle is investigated for root cause and the result feeds back into the process, not just into the individual's work.