Vehicle Inspection

Vehicle inspections protect the driver, passengers, and other road users by identifying unsafe conditions before they cause an accident. Whether you are performing a multi-point inspection as part of a service visit, conducting a state safety inspection, or preparing a vehicle for emissions testing, a systematic approach ensures nothing is missed. This guide covers inspection procedures, pass/fail criteria, common failure items, and the documentation standards you need to know.

Types of Vehicle Inspections

Multi-Point Inspection (MPI)

A comprehensive check performed during routine service visits (oil changes, tire rotations, etc.). Not mandated by law, but expected by dealerships and professional shops. Serves as a sales tool for needed repairs and a customer safety net.

State Safety Inspection

Required in approximately 16 states (as of 2025). Mandated pass/fail criteria vary by state. Covers critical safety items: brakes, tires, lights, steering, suspension, windshield, horn, mirrors, and more. The vehicle must pass to be registered or renewed.

Emissions Inspection

Required in many metro areas and some entire states. Tests whether the vehicle's emissions control systems are functioning properly. May be OBD-II based (plug-in test), tailpipe measurement (sniffer), or visual inspection of emissions components.

Pre-Purchase Inspection

A thorough evaluation of a used vehicle performed before a buyer commits. Should cover every system comprehensively. Typically takes 1-2 hours and may include a road test.

Multi-Point Inspection Procedure

A professional MPI follows a consistent sequence. Most shops use a color-coded system: Green (OK), Yellow (Needs Attention Soon), Red (Needs Immediate Attention/Safety Concern).

Under-Hood Inspection

Engine Oil:

• Check level on the dipstick. Should be between the low and full marks.
• Check color: amber/golden (fresh), dark brown (normal used), black and gritty (overdue for change), milky/frothy (coolant contamination - possible head gasket)
• Smell for burned odor (overheating or breakdown)

Coolant:

• Check level in the reservoir (cold). Should be at or near the cold fill line.
• Visually check color - should match the type specified. Brown, rusty, or oily coolant needs attention.
• Check the radiator cap seal and spring condition
• Inspect hoses for cracks, bulges, soft spots, or weeping at clamp connections
• Check the radiator for bent fins, debris, and external leaks

Transmission Fluid (if equipped with a dipstick):

• Check level and condition at operating temperature
• Fresh ATF is red and translucent. Worn ATF is darker. Brown or burnt-smelling ATF indicates overheating or worn clutches.

Brake Fluid:

• Check level in the reservoir. Should be between MIN and MAX marks.
• Low brake fluid usually means the pads are worn (fluid fills the caliper space as pads thin) or there is a leak
• Check color: clear/light amber (good), dark brown (old, moisture-contaminated, needs replacement)

Power Steering Fluid:

• Check level. Listen for whining from the pump (indicates low fluid or failing pump).

Belts:

• Inspect the serpentine belt for cracks, fraying, glazing, and chunk loss
• Check belt tensioner: the belt should deflect approximately 1/4" to 1/2" with firm thumb pressure between pulleys, or the auto-tensioner should be within its indicator range
• Some belts show wear as rib material loss rather than cracks (use a belt wear gauge if available)

Battery:

• Visual condition: clean terminals, no corrosion, secure hold-down
• Test with a conductance tester: compare CCA to the battery's rated CCA
• Check the date code (most batteries last 3-5 years in hot climates, 4-6 in mild climates)

Air Filter:

• Remove and inspect. Hold up to a light source. If light does not pass through, replace.
• Check the filter box and intake tract for debris, rodent nests, or damage

Windshield Washer Fluid:

• Top off. Check wiper spray pattern and nozzle aim.

Exterior Walk-Around

Lighting:

• Check all exterior lights while an assistant operates the controls, or use a wall/reflection to verify:
  • Headlights (low and high beam)
  • Front and rear turn signals
  • Brake lights (all three, including center high-mount)
  • Taillights and running lights
  • Reverse (backup) lights
  • License plate light
  • Fog lights (if equipped)
  • Hazard flashers
• Check for cracked, fogged, or discolored lenses
• Check headlight aim (many states have specific aim requirements for safety inspection)

Tires:

• Measure tread depth at three points across each tire (inside, center, outside)
• Inspect sidewalls for cracking, bulging, cuts, or embedded objects
• Check for uneven wear patterns (see alignment section)
• Record tire pressures and adjust to door placard specification
• Check the spare tire (if equipped): pressure, tread, and tools
• Check DOT date code: flag tires older than 6 years

Windshield and Glass:

• Check for cracks, chips, and delamination
• Safety inspection: most states fail cracks larger than 6 inches or any crack in the driver's primary viewing area (the swept area of the driver-side wiper)
• Check mirrors for cracks and secure mounting

Wipers:

• Inspect rubber blades for tearing, cracking, or streaking
• Test operation on all speeds
• Typical replacement interval: every 6-12 months

Body and Frame:

• Check for excessive rust, especially on structural components (frame rails, subframe, rocker panels)
• Check for fluid leaks under the vehicle: oil (dark brown/black), coolant (green/orange/pink), transmission fluid (red), power steering fluid (clear/amber), brake fluid (clear/light yellow)

Undercarriage Inspection (on Lift)

Brakes:

• Measure pad thickness with a caliper or calibrated ruler
• Measure rotor thickness with a micrometer (compare to minimum spec)
• Check for rotor scoring, grooving, or heat spots
• Inspect brake hoses for cracks and chafing
• Check brake lines for corrosion, kinks, or leaks (especially in salt-belt states)
• Inspect drum brakes: shoe thickness, wheel cylinder leaks, hardware condition

Steering and Suspension:

• Check tie rod ends: grab the tire at 3 and 9 o'clock and rock it - any play indicates worn tie rods
• Check ball joints: grab the tire at 12 and 6 o'clock and rock it (on SLA front ends). Check for play and torn boots.
• Check wheel bearings: spin the wheel and listen for roughness or growling. Check for play by rocking the wheel at 12 and 6.
• Inspect control arm bushings for cracking and separation
• Check struts/shocks for leaking oil
• Bounce test: push down on each corner and release - the vehicle should return to ride height and stop. More than one oscillation indicates worn dampers.
• Check sway bar links and bushings for play and deterioration
• Inspect CV boots (FWD) and U-joints (RWD/4WD) for tears, grease leaks, and play

Exhaust System:

• Check from the manifold/headers to the tailpipe for leaks, rust-through, loose hangers, and damage
• Shake the catalytic converter to listen for broken substrate (rattling = failed catalyst internals)
• Check for exhaust leaks before the O2 sensors (causes false lean codes)

State Safety Inspection - Common Fail Items

These items cause the most safety inspection failures nationwide:

1. Lighting failures: Burned-out bulbs, cracked lenses, misaimed headlights
2. Tire problems: Tread below 2/32", sidewall damage, mismatched sizes on the same axle
3. Brake issues: Pads below minimum, leaking wheel cylinder, hose damage, low fluid
4. Windshield cracks: In the driver's viewing area
5. Wipers: Torn or inoperative
6. Horn: Inoperative
7. Exhaust leaks: Especially forward of the passenger compartment
8. Steering play: Excessive free play in the steering wheel (typically more than 2 inches for manual steering, 3 inches for power steering on vehicles with a steering box)
9. Suspension: Broken springs, leaking struts, worn ball joints with excessive play
10. Mirrors: Missing, cracked, or loose side mirrors

OBD-II Emissions Inspection

Most state emissions programs (post-2000 vehicles) use an OBD-II plug-in test rather than a tailpipe sniffer.

What the OBD-II Test Checks:

1. Malfunction Indicator Lamp (MIL/Check Engine Light): Must be OFF. A MIL that is on is an automatic fail.
2. Stored DTCs: Any emissions-related DTC is a fail.
3. Readiness monitors: A maximum number of monitors can be "not ready" (varies by state - typically 0-1 for 2001+ vehicles, 0-2 for 1996-2000 vehicles).
4. Communication: The scan tool must be able to communicate with the vehicle's PCM.

Common Emissions Failures and Fixes

Failure	Common Code	Typical Fix
Catalytic converter efficiency	P0420/P0430	Replace catalytic converter (after confirming upstream O2 sensors are good)
EVAP small leak	P0442	Gas cap, EVAP hose crack, purge valve, vent valve
EVAP large leak	P0455	Missing or broken gas cap, major hose disconnection
O2 sensor circuit	P0130-P0167	Replace failed O2/AF sensor
Misfire	P0300-P0312	Plugs, coils, injectors, or mechanical
EGR flow	P0401	Clean or replace EGR valve, clean intake ports
Thermostat	P0128	Replace thermostat (monitors require operating temp)

Readiness Monitor Drive Cycle Tips

If monitors are "not ready" after a repair:

• Ensure the gas tank is between 1/4 and 3/4 full (EVAP monitor needs this)
• Drive a mix of city and highway for 30-60 minutes with varied speeds
• Include a cold start, warm-up idle, steady-state cruise at 55 mph, and deceleration
• Specific drive cycles vary by manufacturer - consult the service manual for stubborn monitors

Pre-Purchase Inspection Checklist

A thorough pre-purchase inspection should include everything in the MPI above, plus:

• Vehicle history report: Check for accidents, title issues, odometer rollback
• Frame inspection: Check for accident repair evidence (mismatched paint, uneven panel gaps, welding marks on structural components)
• Compression test: Especially on high-mileage vehicles (over 100K)
• Road test: 15-20 minutes covering city and highway driving. Check for:
  • Straight tracking (let go of the steering wheel briefly on a flat road)
  • Smooth shifting (automatic) or easy engagement (manual)
  • No vibrations at speed
  • Effective braking with no pulsation or pulling
  • No unusual noises (clunks, whines, rattles)
  • A/C blows cold (should be 35-45 deg F at the center vent)
  • Heater blows hot
  • All electronics function (windows, locks, radio, backup camera)
• Scan tool check: Read all modules for stored codes, not just the engine

Documentation and Reporting

• Record all findings on a standardized inspection form with the customer's information, vehicle details, mileage, and date
• Use the color-coded system (green/yellow/red) for easy customer understanding
• Include measurements (pad thickness in mm, tread depth in 32nds, battery CCA)
• Take photos of any concerning findings to show the customer
• Present the inspection results to the customer in person - explain priorities and safety concerns
• File the inspection record for future reference and liability protection

Key Takeaways

• Follow a consistent inspection sequence every time - checklists prevent missed items
• Measure, do not guess. Use gauges, micrometers, and testers for objective results.
• Separate safety items (red) from maintenance items (yellow) when communicating with customers
• OBD-II readiness monitors must be complete for an emissions test to pass - do not clear codes and send a customer straight to the test station
• Document everything: measurements, photos, and customer communication
• A thorough inspection builds trust and identifies revenue opportunities for the shop