Why does 3400 Chevy have 2 crank sensors?

The 3400 Chevy engine, specifically the 3400 L67 Supercharged engine found in some GM vehicles (like the Grand Prix GTP), uses *two* crankshaft position sensors (CKP sensors) for redundancy and improved performance/reliability. While not strictly necessary for basic engine operation in a way that one sensor is, the second provides:

* Improved Accuracy and Reliability: Having two sensors allows for cross-referencing the crankshaft's rotational position. If one sensor fails, the other can still provide a signal, preventing a complete engine shutdown. This is particularly important in a high-performance engine like the supercharged L67.

* Enhanced Fault Detection: The engine control module (ECM) can compare signals from both sensors. Any discrepancies could indicate a problem with one of the sensors or another component related to crankshaft position, enabling earlier diagnosis and preventing more serious damage.

* Improved Ignition Timing Precision: Precise ignition timing is crucial for power and efficiency. Using two sensors allows for more accurate and refined timing control, optimizing the engine's performance.

In short, while a single CKP sensor *could* work, using two in the 3400 L67 provides a significantly improved level of redundancy, reliability, and performance. The extra cost and complexity are justified by the benefits in a high-output engine. This is a common practice in higher-performance or safety-critical automotive applications.