ASE Practice Test #5 3 — Questions and Answers
Question 1: A technician is testing an ignition coil on a COP (coil-on-plug) system. The coil primary resistance tests within specification. What additional test should be performed?
- No further testing needed — primary resistance confirms coil condition
- Test the secondary resistance (high-voltage winding) of the coil using the specified high-range resistance scale and compare to specification (Correct answer)
- Test the coil output with an oscilloscope only at the ECM
- Replace the coil regardless of test results as a precaution
Correct answer: Test the secondary resistance (high-voltage winding) of the coil using the specified high-range resistance scale and compare to specification
An ignition coil has two windings: the primary (low voltage, low resistance — typically 0.5–2 ohms) and the secondary (high voltage, high resistance — typically 6,000–15,000 ohms). Testing only the primary confirms the trigger circuit, but the secondary can fail (open or shorted windings) while the primary tests fine. A failed secondary produces insufficient spark energy, causing misfires especially at high RPM or under load. Both primary and secondary resistance must be measured to fully evaluate the coil.
Question 2: What is the purpose of the TPMS (Tire Pressure Monitoring System) sensor, and what triggers an illuminated TPMS warning light?
- TPMS monitors tire tread depth — a light comes on when tread is below 2/32"
- TPMS uses pressure sensors in each wheel to monitor tire inflation — the warning light illuminates when one or more tires is 25% or more below the vehicle's recommended inflation pressure (Correct answer)
- TPMS controls automatic tire inflation from the vehicle's air system
- The TPMS light only illuminates during wheel speed sensor failures
Correct answer: TPMS uses pressure sensors in each wheel to monitor tire inflation — the warning light illuminates when one or more tires is 25% or more below the vehicle's recommended inflation pressure
Federal law (TREAD Act) requires TPMS on all new vehicles sold in the US after 2008. TPMS sensors mounted in each wheel transmit pressure data to a receiver module. The TPMS warning light illuminates when any tire's pressure drops to 25% below the placard recommended pressure — alerting the driver of a potentially dangerous condition. Underinflated tires reduce handling, increase stopping distances, and risk overheating and blowout. After inflating tires, many systems require a relearn procedure to reset the warning light.
Question 3: What is the difference between "hard" and "soft" diagnostic codes (DTCs)?
- Hard codes are only stored in diesel ECMs; soft codes are only in gasoline ECMs
- A hard (current) code indicates a fault that is present right now; a soft (intermittent) code was detected at some point but is not currently active — the condition comes and goes (Correct answer)
- Hard codes require immediate engine shutdown; soft codes are informational only
- Hard codes are stored in permanent memory; soft codes erase when the key is turned off
Correct answer: A hard (current) code indicates a fault that is present right now; a soft (intermittent) code was detected at some point but is not currently active — the condition comes and goes
In automotive diagnostics, "hard" codes indicate a fault that is currently active — the failure condition exists right now and can typically be diagnosed during that session. "Soft" or "intermittent" codes indicate a fault that was detected during a previous drive cycle but is not currently present. Intermittent codes are more challenging to diagnose because the fault may not be reproducible immediately. Checking freeze frame data and using enhanced data logging to capture the fault during operation are strategies for diagnosing soft codes.
Question 4: A vehicle has a complaint of "hesitation during acceleration from a stop." The MAP sensor, MAF sensor, and O2 sensors all read correctly. Which component is MOST likely causing the hesitation?
- The thermostat is opening too early
- A faulty throttle position sensor (TPS) that has a dead spot or dropout in the signal during initial throttle opening — the ECM receives no accurate throttle position data at tip-in (Correct answer)
- Low transmission fluid level
- A faulty camshaft position sensor
Correct answer: A faulty throttle position sensor (TPS) that has a dead spot or dropout in the signal during initial throttle opening — the ECM receives no accurate throttle position data at tip-in
Hesitation on initial acceleration (tip-in hesitation) from a stop is a classic symptom of a throttle position sensor with a "dead spot" — a section of the resistive track that has worn away, causing a momentary dropout in the signal as the throttle initially opens. The ECM uses TPS data for accelerator enrichment (similar to the old accelerator pump in a carburetor). If TPS signal drops out during tip-in, the ECM does not provide proper enrichment, causing a momentary lean stumble. Monitoring TPS voltage on a scan tool while slowly opening the throttle reveals voltage dropouts.
Question 5: What is the purpose of a four-gas exhaust analyzer in automotive diagnosis, and what do high HC readings specifically indicate?
- Four-gas analysis measures coolant, oil, transmission fluid, and exhaust quality
- A four-gas analyzer measures HC (hydrocarbons), CO (carbon monoxide), CO2 (carbon dioxide), and O2 (oxygen) in exhaust — high HC readings indicate unburned fuel from misfires, ignition failure, rich running, or low compression (Correct answer)
- HC readings indicate catalytic converter substrate temperature
- High HC means the oxygen sensors are functioning correctly
Correct answer: A four-gas analyzer measures HC (hydrocarbons), CO (carbon monoxide), CO2 (carbon dioxide), and O2 (oxygen) in exhaust — high HC readings indicate unburned fuel from misfires, ignition failure, rich running, or low compression
A four-gas exhaust analyzer measures the chemical composition of exhaust gases and provides direct insight into combustion quality. HC (hydrocarbons) represents unburned or partially burned fuel — elevated HC always indicates a combustion problem: misfires from bad ignition components, fuel-soaked plugs, low compression, rich air-fuel mixture, or retarded timing. CO indicates the richness of combustion. CO2 reflects combustion efficiency (higher is better, max ~14.5%). O2 shows excess air. Together these gases paint a complete picture of engine combustion health.
Question 6: Which ASE certification area covers diagnosis and repair of automatic transmission slipping, delayed engagement, and harsh shifting?
- A1 — Engine Repair
- A2 — Automatic Transmission/Transaxle (Correct answer)
- A4 — Steering and Suspension
- A6 — Electrical/Electronic Systems
Correct answer: A2 — Automatic Transmission/Transaxle
ASE certification A2 covers Automatic Transmission and Transaxle diagnosis and repair. The A2 exam includes diagnosing and repairing hydraulic pressure concerns, clutch pack and band adjustment, converter clutch operation, electronic shift controls, and fluid condition issues. Slipping, delayed engagement, and harsh shifting are covered in the A2 content area under general diagnosis and transmission mechanical/hydraulic/electronic system repair. Technicians pursuing A2 certification demonstrate competency in all aspects of automatic transmission service.
ASE Practice Test #5 3
A technician is testing an ignition coil on a COP (coil-on-plug) system.
The coil primary resistance tests within specification.
What additional test should be performed?