SKM Motor Vehicle Mechanic Level 3 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

CO exposure limit

OSHA general industry permissible exposure limit for carbon monoxide is 50 ppm as an 8-hour time-weighted average, with a 200 ppm short-term limit not exceeding 5 minutes in any 2 hours.

Refrigerant venting prohibition

Section 608 of the Clean Air Act prohibits knowingly venting ozone-depleting and substitute refrigerants during service, maintenance, repair, or disposal of appliances and motor vehicle air conditioners.

Flammable liquid threshold

A liquid with a flash point below 60 degrees Celsius is classified as flammable; storage in approved cabinets is limited to 60 gallons per cabinet for most shop solvents.

Lockout tagout verification

Each worker applies a personal lock and tag, then verifies zero energy state by attempting start or testing voltage before beginning work on the equipment.

Micrometer reading rule

The reading equals the sleeve value plus the thimble value times 0.01 mm for a metric micrometer; add 0.5 mm whenever a half-millimeter sleeve mark is exposed.

Torque wrench calibration

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

Cylinder leakage test

With the cylinder at top dead center on compression and regulated air applied, leakage heard at the intake, exhaust, or crankcase identifies valve or ring sealing faults.

Fuel trim interpretation

Long-term fuel trim above about plus 10 percent indicates a lean condition such as a vacuum leak or low fuel pressure; negative trim indicates a rich condition.

Stoichiometric ratio meaning

For gasoline the stoichiometric air-fuel ratio is about 14.7 to 1 by mass; lambda equals 1.00 whenever the actual ratio matches the fuel's stoichiometric requirement.

Clutch pedal free play

Free play is typically 10 to 25 mm; too much prevents full disengagement and causes gear clash, while none causes release bearing wear and clutch slip.

Differential backlash measurement

Backlash is measured with a dial indicator on a ring gear tooth, commonly 0.13 to 0.20 mm, and is corrected by changing shim thickness during assembly.

Torque converter stall test

With brakes held and throttle briefly applied in Drive, abnormally low stall speed suggests engine or stator faults, while high stall speed suggests slipping clutch packs.

DOT brake fluid classes

DOT 3 and DOT 4 are glycol-based and absorb moisture; DOT 5 is silicone-based and must never be mixed with glycol fluid because compatibility and boiling points differ.

Camber caster toe

Camber is wheel vertical tilt, caster is steering axis tilt affecting straight-line stability, and toe is the front-to-rear difference across the tires.

Brake disc runout limit

Lateral runout is typically limited to about 0.05 mm; excessive runout causes pedal pulsation and requires resurfacing within the stamped minimum thickness or replacement.

Ohm law and power

Voltage equals current times resistance, and power equals voltage times current; a 12 volt circuit drawing 5 amps has 2.4 ohms and dissipates 60 watts.

Battery state of charge

Open-circuit voltage near 12.6 volts indicates full charge, 12.4 volts about 75 percent, 12.2 volts about 50 percent, and 12.0 volts about 25 percent.

CAN bus resistance check

With power off, resistance between CAN high and CAN low near 60 ohms indicates both 120 ohm terminators are intact; about 120 ohms indicates an open terminator or bus break.

Voltage drop limit

Voltage drop is measured under load with the circuit operating; more than 0.5 volts on a power feed or ground indicates excessive resistance in that path.

PAG versus mineral oil

R-134a systems use polyalkylene glycol oil, while R-12 systems used mineral oil; mixing oils or refrigerants contaminates the system and damages the compressor.

Evacuation hold test

After evacuation, the system should hold vacuum for at least 10 to 15 minutes; a vacuum that rises during the hold indicates a leak in the system.

Blower high speed only

A blower that operates only on the highest speed usually indicates an open blower resistor or failed blower control module rather than a failed motor.

Four gas exhaust analysis

High hydrocarbons indicate misfire or unburned fuel, high carbon monoxide indicates a rich mixture, and high carbon dioxide with low oxygen indicates efficient combustion.

OBD readiness monitors

Readiness monitors must be complete before an emissions test; clearing codes resets them, and a manufacturer drive cycle is needed to set them again.

Battery load test

Apply half the cold cranking amp rating for 15 seconds; battery voltage should remain above 9.6 volts at 20 degrees Celsius for the battery to pass.

Three Cs of documentation

A repair order records the customer complaint, the verified cause, and the correction performed, along with parts, labor time, and technician identification.

Declined repair documentation

When a customer declines recommended work, record the recommendation, the customer's decision, and the date to protect both parties if a related failure occurs later.

Plain language explanation

State the symptom, the verified cause, the recommended repair, and the consequence of deferring it, avoiding jargon and confirming the customer's understanding.

Four step job instruction

On-the-job training follows prepare the learner, present the task, let the learner practice, and follow up with evaluation against the task standard.

Skills matrix purpose

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

Incident investigation record

The record captures the sequence of events, root cause, and corrective action; near misses are also recorded and reviewed with the team.

Job briefing content

A pre-task briefing covers hazards, required personal protective equipment, tools, and the work sequence, with attendance documented for high-risk tasks.