In a modern common rail diesel engine, the ECM controls fuel injection timing and duration. If a faulty crankshaft position sensor is providing incorrect timing signals, how might this impact injection timing?

Question: In a modern common rail diesel engine, the ECM controls fuel injection timing and duration. If a faulty crankshaft position sensor is providing incorrect timing signals, how might this impact injection timing?

Answer options: ✅ The ECM would resort to a fixed, default injection timing, leading to poor performance.

• The ECM would compensate by increasing fuel pressure, causing over-fuelling.
• The ECM would advance injection timing to prevent pre-ignition.
• The ECM would retard injection timing to reduce NOx emissions.

Correct answer: The ECM would resort to a fixed, default injection timing, leading to poor performance.

Explanation: A faulty crankshaft position sensor provides inaccurate or no data to the ECM regarding piston position, which is critical for precise injection timing. Without this accurate data, the ECM cannot correctly synchronize fuel injection, often resulting in erratic operation or reverting to a limp-home mode with fixed, suboptimal timing.