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Practice questions · 310S H

Diagnoses and repairs hybrid and electric vehicle (EV) systems

2 questions from this exam area, each with the full explanation shown — not just the answer. Free, no account.

7% of the exam

1

A technician is testing a 5-pin relay from a cooling fan circuit. The relay has pins 85, 86, 30, 87, and 87a. With the relay unpowered, the DMM shows continuity between pins 30 and 87a. This indicates:

  1. The relay is shorted and must be replaced.
  2. Pin 87a is the Normally Closed (N.C.) contact.Answer
  3. Pin 87a is the Normally Open (N.O.) contact.
  4. The relay's control coil is good.

Why that is right

In relay terminology 'normally' means the de-energized (at-rest) state. Pin 30 is the common contact, so continuity between pin 30 and pin 87a with the coil unpowered proves that 87a is the Normally Closed (N.C.) contact.

Why the other options are wrong

  • The relay is shorted and must be replaced. — This continuity is the expected behavior of a good 5-pin SPDT relay, not a fault; it shows the N.C. path is intact, so the relay should not be condemned.
  • Pin 87a is the Normally Open (N.O.) contact. — The Normally Open contact (pin 87) is open at rest and would show no continuity to pin 30 until the coil is energized, so 87a cannot be the N.O. contact here.
  • The relay's control coil is good. — Testing across 30 and 87a checks the switch/contact side of the relay; the control coil is tested across pins 85 and 86, so this reading says nothing about coil condition.

2

When does an "overdrive" ratio (where the wheels turn faster than the engine) occur in a power split device?

  1. When MG1 (on the sun gear) is stopped.
  2. When MG1 (on the sun gear) is turning slower than the ICE (on the carrier).
  3. When MG1 (on the sun gear) is turning faster than the ICE (on the carrier).Answer
  4. When MG1 and MG2 match speeds.

Why that is right

In a power-split (planetary) device, overdrive occurs when MG1 on the sun gear spins faster than the ICE on the carrier; this drives the ring gear (output) faster than the engine, so the wheels turn faster than the engine.

Why the other options are wrong

  • When MG1 (on the sun gear) is stopped. — When MG1 is stopped, the sun gear is held and the ring output turns slower than the carrier, giving a reduction (underdrive), not overdrive.
  • When MG1 (on the sun gear) is turning slower than the ICE (on the carrier). — When MG1 turns slower than the ICE, the output is still below engine speed, so this produces underdrive rather than overdrive.
  • When MG1 and MG2 match speeds. — MG1 and MG2 matching speeds describes a locked/direct-drive-like condition, not the sun-gear overspeed that creates an overdrive ratio.

Exam-style practice written to the published Red Seal standard. These are not real exam questions — the official Red Seal sample questions are deliberately excluded from everything we publish.

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