I am trying to find the location for my crankshaft position sensor on my 1999 Mitsubishi Diamante

Your 1999 Mitsubishi Diamante is a 3.5L MFI SOHC 6cyl engine.
MFI = multi-port fuel injection
SOHC = single overhead camshaft
This answer covers Mitsubishi Diamante1.8L, 2.4L, 3.0L (SOHC and DOHC), 3.5L, and 1997-2000 1.5L Engines.

2.4L engine shown, others similar.

Fig.1 - CKP position and its two mounting bolts


In Fig. 1, the two arrows point to the CKP (crankshaft position sensor) mounting bolts to remove. 2.4L engine shown.

Fig.2 - CKP reluctor removal

Remove the sensor and slide the reluctor wheel off of the crankshaft-2.4L engine shown.

1. Disconnect the negative battery cable.
2. Remove the timing belt.
3. Unplug the sensor connector.
4. Unfasten the two retaining bolts, then remove the CKP sensor from the vehicle.
5. Installation is the reverse of the removal procedure.

Reference: Autozone online repair guide: Mitsubishi Galant/Mirage/Diamante 1990-2000, at
www.autozone.com

Fig.3 - photo - new 99Diamante CKP, a Wells part #SU4313