20 Automotive Mechanic Assessment Quiz

Toyota specifies 5 minutes for capacitor discharge after service plug removal. This is manufacturer-specific - other brands may have different requirements. Voltage testing requires special high-voltage meters and isn't the standard protocol.

Pressure should drop at idle due to manifold vacuum on the regulator. When vacuum line is removed, pressure should rise. No change indicates a stuck regulator not responding to vacuum changes.

High low-side pressure with normal high-side pressure indicates restricted metering device (expansion valve/orifice tube). Overcharge would show high pressure on both sides; undercharge would show low pressure both sides.

Slow pedal sink with no external leaks indicates internal master cylinder bypass past worn seals. Booster issues affect pedal effort, not sinking. ABS/proportioning valve issues would show different symptoms.

Modern vehicle programming requires stable voltage above 13.0V throughout the process. Even with good battery voltage, programming draws significant current. External power supply ensures stable voltage preventing corruption during critical programming phases.

CAN High at 2.5V and CAN Low at 2.5V is normal idle state (some variance acceptable). Since other modules communicate, the network is functional. ABS module likely has power/ground issues preventing operation.

Both banks running lean with similar fuel trim corrections indicates a common cause affecting both banks - typically a large vacuum leak after the MAF sensor. Individual bank issues would show different patterns.

Frequent regeneration indicates the DPF isn't getting clean during regeneration cycles, often due to incomplete burns caused by low exhaust temperature, fuel system issues, or sensor problems preventing proper regeneration.

Voltage dropping below 10V during cranking indicates insufficient battery capacity. 12.4V static is borderline (should be 12.6V+), and while charging voltage is acceptable, the cranking test reveals the true problem.

PCM circuits should draw 25-50mA maximum. 145mA drop (180-35) indicates excessive current in PCM-controlled circuits, requiring systematic investigation of modules/components on that circuit.

Pull during driving but not braking, with even tire wear, indicates caster difference between sides. Brake drag would cause pull during braking and uneven wear. Bearing/pressure issues would affect both driving and braking.

Rising oil temperature with declining pressure while coolant temperature remains stable indicates developing oil system issues - likely pump wear, pickup screen restriction, or internal clearance increases. This pattern enables predictive maintenance intervention.

Shift points are primarily controlled by throttle position and vehicle speed inputs. A consistently high shift point with normal feel suggests slightly high TPS signal causing the PCM to interpret higher load than actual.

Proper sequence is: eliminate ignition sources first, provide ventilation to prevent vapor accumulation, then use explosion-proof lighting for inspection. Options A and B miss critical steps, while D creates additional hazards.

Dark red color with burnt odor and metallic particles indicates severe overheating and internal clutch/band material breakdown. Normal service fluid wouldn't have metallic particles or burnt smell.

Inner edge wear with proper pressure typically indicates excessive negative camber. Tire rotation wouldn't cause this pattern, and under-inflation would show outer edge wear first.

8% overnight loss (approximately 6-8 kWh) is excessive even for Tesla vampire drain (should be 1-3% maximum). Isolation resistance is excellent (680 megohms), so the issue is parasitic draw in 12V or HV systems requiring systematic diagnosis.

Most modern ADAS systems require both static calibration (targets in controlled environment) followed by dynamic calibration (road test) to verify proper operation under real-world conditions.

0.8mS spark line with 1.2mS burn time and normal oscillations indicates proper ignition performance. Lean mixtures show longer spark duration; rich mixtures show shorter duration; worn plugs show irregular patterns.

Contaminated MAF sensors typically under-report airflow, causing the PCM to deliver insufficient fuel, triggering positive fuel trim corrections to compensate for lean conditions.