Free T1 Practice Questions

Question 1

A Class 5 gasoline delivery truck has a rough warm idle and lean-mixture codes for both cylinder banks. In closed loop, long-term fuel trims are +23% and +25% at idle, but fall to +3% and +4% at 2,500 rpm without load. Short-term trims remain near zero at both speeds. Fuel pressure meets specification, and no exhaust leaks are found ahead of the oxygen sensors. Which test should receive priority?

Accepted Answer

Smoke-test the intake manifold and its vacuum connections for leaks.

Answer

Check fuel-pump delivery volume under sustained engine load.

Answer

Compare the mass-airflow sensor output with a known-good airflow trace.

Answer

Test both upstream oxygen sensors for a persistent lean-signal bias.

Question 2

A truck cranks slowly even though its battery passes a load test. During cranking, voltage measured directly across the battery posts is 10.7 V. The drop from the positive post to the starter B+ terminal is 0.18 V; the drop from the starter housing to the negative post is 1.25 V. Service information allows no more than 0.30 V on either path. Where should the technician isolate the excessive resistance?

Accepted Answer

Between the starter housing and the battery negative post.

Answer

Between the battery positive post and the starter B+ terminal.

Answer

Across the starter relay contacts in the control circuit.

Answer

Inside the starter motor at the brush connections.

Question 3

After a valve adjustment, a gasoline engine with mechanical valve lash runs smoothly cold but misfires at hot idle. The exhaust-valve specification is 0.016-0.020 in., measured cold with each cam lobe on its base circle. Two exhaust valves now measure 0.002 in. cold. Ignition and injector operation on those cylinders are normal. What is the appropriate first correction?

Accepted Answer

Readjust the exhaust valves cold, then repeat the hot-idle test.

Answer

Set the hot exhaust valves to the cold-clearance specification.

Answer

Remove the head and renew the two exhaust valves and seats.

Answer

Replace the affected valve springs before resetting the lash.

Question 4

Low-signal codes appear together for the manifold-pressure and throttle-position sensors. The wiring diagram shows that both share a five-volt reference with the A/C refrigerant-pressure sensor. The reference measures 0.6 V at all three connectors. Unplugging only the refrigerant-pressure sensor restores 5.0 V and normal readings from the other two sensors; reconnecting it reproduces the fault. The harness remains stationary during repeated checks. What do these results establish?

Accepted Answer

The refrigerant-pressure sensor branch is pulling down the shared reference.

Answer

The throttle-position signal wire is open between its sensor and the ECM.

Answer

The manifold-pressure sensor's ground circuit is open.

Answer

The ECM's five-volt regulator has an internal open requiring module replacement.

Question 5

An overhaul worksheet records the following measurements:
Piston skirt at the specified gauge point: 3.9992 in.
Piston crown: 3.9970 in.
Finished bore at the prescribed checking location: 4.0016 in.
Specified piston-to-cylinder clearance: 0.0018-0.0030 in.
Bore taper and out-of-round are within limits. Which clearance and assembly decision are correct?

Accepted Answer

0.0024 in.; this piston and cylinder meet the clearance specification.

Answer

0.0012 in.; increase the clearance before assembling this piston.

Answer

0.0046 in.; select a piston that provides less clearance.

Answer

0.0048 in.; machine for an approved oversize piston.

Question 6

Every fuel stop is followed by a hard start and a brief rough idle; the truck otherwise runs normally. Its EVAP purge valve is normally closed when de-energized. With purge commanded off, manifold vacuum is present at the valve's canister-side port. Vacuum remains there after the electrical connector is unplugged. The tank vent path is unrestricted. Which repair is supported by the valve test?

Accepted Answer

Replace the canister purge valve because it does not seal.

Answer

Replace the canister vent valve because it is not sealing.

Answer

Replace the fuel tank pressure sensor because it is biased.

Answer

Reprogram the ECM because it is commanding excessive purge.

Question 7

Cylinder 6 of a gasoline V8 produces 86 psi on a cranking compression test; the other seven produce 171-179 psi. Adding the specified amount of oil raises cylinder 6 to only 89 psi. During leak-down testing at top dead center on its compression stroke, strong airflow is heard at the throttle body, with no unusual airflow at the tailpipe and only faint crankcase leakage. Where is the principal compression loss?

Accepted Answer

Across an intake valve's sealing contact with its seat.

Answer

Between the compression rings and the cylinder wall.

Answer

Through the head gasket into an adjacent combustion chamber.

Answer

Across an exhaust valve's sealing contact with its seat.

Question 8

During a secured, stationary power-take-off load test, a mechanical oil-pressure gauge falls from 42 psi to 3 psi at 1,500 rpm. The engine's minimum specification at that speed and oil temperature is 30 psi. A deep knocking sound begins, and the oil-pressure warning illuminates. What takes priority?

Accepted Answer

Disengage the power take-off and shut down the engine.

Answer

Reduce the engine to idle and listen for the source of the knock.

Answer

Raise engine speed briefly to see whether oil pressure recovers.

Answer

Continue at light load while checking the oil-pressure sender circuit.

Question 9

Several spark plugs removed for inspection have a light tan ring on the outside of the ceramic, immediately above the metal shell. The discoloration extends around the insulator rather than forming a narrow track toward the terminal. The firing ends and plug boots are intact, and the truck has no misfire. What does this appearance indicate?

Accepted Answer

Normal corona staining on the exposed ceramic insulator.

Answer

Combustion gases leaking past the seal between the insulator and shell.

Answer

An external flashover path carrying ignition voltage directly to ground.

Answer

Overheating that has glazed the insulator at the firing end.

Question 10

A utility truck's battery goes flat after two days parked. Battery capacity and charging-system tests pass. Ten minutes after the last door was closed, a current logger still reads 1.2 A. The manufacturer's procedure allows up to 45 uninterrupted minutes for module sleep and specifies a settled draw below 50 mA. How should the draw be evaluated next?

Accepted Answer

Leave the truck undisturbed and log current through the specified sleep period.

Answer

Pull fuses one at a time now until the current falls below 50 mA.

Answer

Disconnect the battery overnight and compare its voltage the following morning.

Answer

Isolate the alternator from the circuit now and repeat the draw test.

Free T1 Practice Questions

Domain 1: General Engine Diagnosis 28% of exam

Question 1

Question 2

Question 3

Domain 2: Cylinder Head and Valve Train Diagnosis and Repair 8% of exam

Question 4

Domain 3: Engine Block Diagnosis and Repair 8% of exam

Question 5

Domain 4: Lubrication and Cooling Systems Diagnosis and Repair 6% of exam

Question 6

Domain 5: Ignition System Diagnosis and Repair 12% of exam

Question 7

Domain 6: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair 12% of exam

Question 8

Domain 7: Emissions Control Systems Diagnosis and Repair 10% of exam

Question 9

Domain 8: Computerized Engine Controls Diagnosis and Repair 16% of exam

Question 10

That's 10 of 1,030