To find it, you'll need to do some hands-on investigation:
1. Consult a Repair Manual: A Haynes or Chilton repair manual specific to your 1988 Pontiac LeMans with the 1.6L engine is your best bet. These manuals will have diagrams showing the sensor's location.
2. Visual Inspection: The crank sensor is usually mounted on the engine block, near the crankshaft pulley, but it could be on the transmission bell housing in some cases. Look for a small sensor with a single wire connector. It might be near the oil pan or distributor (if equipped).
3. Follow the Wiring: If you can locate the crank sensor's wire harness connector (it's usually a single wire or a small bundle), trace the wiring back to the sensor itself. This can be a more effective method than just visually searching the engine.
4. Use a Shop Manual/Online Diagram (If Possible): Some online resources might have diagrams for that specific engine, but finding a reliable one for such an older model can be difficult.
Remember to be careful when working near the engine. Disconnect the negative battery cable before beginning any work.