Electronic Engine Management Questions and Answers

Answer: A

A knock sensor detects abnormal combustion vibration and says nothing about how much air the engine is drawing. The other three are the recognised load determination strategies. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Checking which component actually carries the load settles most questions of this kind at once.

Answer: B

A fixed size leak is a large proportion of the small idle airflow and a negligible one at load. That load dependence is the signature of a vacuum leak rather than a proportional fuelling error. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Tracing the requirement back to the physical constraint that produces it makes the answer follow.

Answer: C

Open loop applies during warm up, at full load and on overrun, when feedback is either unavailable or deliberately suspended. Most of a journey's emissions are produced during that warm up period. Naming what changes and what stays the same is the reliable route through questions of this shape. Most errors here come from carrying across a result from a neighbouring case where it does not hold. The shared behaviour explains why these belong together and the differences explain why both exist.

Answer: D

Freeze frame captures the moment, the readiness monitor says whether a test has run, and long term trim is the stored correction. All three appear in a generic scan tool and each answers a different question. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. Naming what changes and what stays the same is the reliable route through questions of this shape. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.

Answer: A

Controllers keep a permanent feed for adaptations and control their own main relay so they can run on after shutdown. The last option describes exactly that arrangement, which makes it a correct and more detailed version of the same answer. The order in which the effects act is what decides the outcome, so it is worth establishing first. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: B

The unit holds its own relay closed to write memory and to run cooling where required. The last option lists exactly those two functions, which makes it a correct and more specific restatement. Checking which component actually carries the load settles most questions of this kind at once. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: C

Interrupting the run on can lose the values being written. Relearning genuinely follows, which makes the last option a correct description of the consequence. Waiting a minute after shutdown avoids it. Tracing the requirement back to the physical constraint that produces it makes the answer follow. The order in which the effects act is what decides the outcome, so it is worth establishing first. A symptom that appears under one condition and not another is what narrows the diagnosis quickly.

Answer: D

Power stage earths carry amps while signal earths carry milliamps, and mixing them corrupts readings. The last option states exactly that reasoning, which makes it a correct and more explanatory version of the same answer. The shared behaviour explains why these belong together and the differences explain why both exist. Checking which component actually carries the load settles most questions of this kind at once. The order in which the effects act is what decides the outcome, so it is worth establishing first.

Answer: A

A common impedance in the earth shifts every reading and confuses every strategy. The last option describes exactly how that presents, which makes it a correct and more useful statement for diagnosis. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Checking which component actually carries the load settles most questions of this kind at once.

Answer: B

Volt drop under operating conditions reveals resistance an ohmmeter cannot resolve. The last option explains exactly why, which makes it a correct and more instructive version of the same answer. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. The shared behaviour explains why these belong together and the differences explain why both exist. Tracing the requirement back to the physical constraint that produces it makes the answer follow.