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ASE Transit Bus

H2 Transit Bus — Diesel Engines — practice test

Studying for H2 (Transit Bus — Diesel Engines)? Overhaul Prep has 171 verified H2 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.

171H2 questions
100%with explanations
9,711questions in total
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Sample H2 questions

Straight from the bank — answers highlighted, with the explanation underneath.

Diesel exhaust fluid (DEF) used in an SCR aftertreatment system is a solution of:

  1. 32.5% urea and 67.5% deionized water
  2. 50% urea and 50% distilled water
  3. Pure anhydrous ammonia
  4. 32.5% ammonia and 67.5% diesel fuel
WhyDEF meeting ISO 22241 is 32.5% high-purity urea and 67.5% deionized water; heat in the exhaust decomposes the urea to ammonia, which then reacts with NOx over the SCR catalyst.

Two technicians discuss a diesel that is hard to start and runs rough. Technician A says air leaking into the fuel on the suction side can cause this. Technician B says a loose or cracked line fitting between the tank and transfer pump can draw air in. Who is correct?

  1. Technician A only
  2. Technician B only
  3. Both Technicians A and B
  4. Neither Technician
WhyAir drawn into the low-pressure suction side (loose fittings, cracked lines, bad filter seals) causes hard starting, rough running, and power loss; both technicians describe valid sources.

A diesel bus loses coolant with no external leak and emits white, sweet-smelling exhaust. The MOST likely cause is:

  1. A plugged air filter
  2. A worn serpentine belt
  3. An internal coolant leak (EGR cooler, head gasket, or cracked head)
  4. A dirty fuel filter
WhyCoolant loss without an external leak plus white sweet smoke indicates coolant entering the combustion/exhaust path through an EGR cooler, head gasket, or crack.

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