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Difficulty: MediumDrawing Logical Conclusions

Read the following passage:

Standard zirconia oxygen sensors in internal combustion engines generate a reliable voltage signal only after reaching an operating temperature of approximately 600°F (315∘C315^\circ\text{C}). To minimize harmful emissions during cold engine starts, modern vehicles incorporate internal ceramic heating elements into the sensor rather than relying solely on hot exhaust gas. Until the sensor reaches this activation threshold, the engine control module operates in "open-loop" mode, calculating fuel delivery strictly from preset base maps and air intake measurements without real-time exhaust feedback.

Statement: Based on the passage, a vehicle with a malfunctioning oxygen sensor heater circuit will take longer to transition out of open-loop mode during a cold start than a vehicle with an operational heater.

Answer: Answer

Answer

True
The statement is strictly supported by the text. The passage establishes that internal ceramic heaters were introduced so sensors would reach the 600°F (315∘C315^\circ\text{C}) activation threshold faster than by exhaust heat alone, and that open-loop mode continues until this threshold is reached. Therefore, a disabled heater forces reliance on exhaust heat alone, extending the duration of open-loop operation during a cold start.

Step-by-Step Solution

1
Identify the conditions required for the engine control module to exit open-loop mode.
The sensor must reach an activation threshold of approximately 600°F (315∘C315^\circ\text{C}) to provide the real-time feedback required to exit open-loop mode.
The passage specifies that open-loop operation continues until the sensor attains this operating temperature.
2
Determine the functional role of the internal ceramic heating element during a cold start.
The ceramic heater warms the sensor to operating temperature faster than relying solely on hot exhaust gas.
The text states that manufacturers added heaters rather than relying entirely on exhaust gas warming.
3
Synthesize the impact of a failed heater circuit on warm-up time and operating mode.
Without the heater, the sensor relies exclusively on slower exhaust warming, extending the time needed to reach 600°F (315∘C315^\circ\text{C}) and prolonging open-loop mode.
Connecting the purpose of the heater to the operational condition proves the statement is logically valid.

Key Concept

Synthesizing passage constraints to deduce the operational outcome of a failed component in a technical system.
Estimated Time:1m 0s
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