OC means Open Circuit. The OHC is smart enough to display that - it will also display SC if the two wires are shorted. Check the connector with the violet/green and black/light blue wires around or under the front end of the power distribution center. Unplug it and use your multimeter on the 20k ohms scale to check the wiring leading down past the battery - if it reads as open, the problem lies in that wiring harness or the sensor itself. If it reads as a value in the 10k range or so (may be different depending on your weather) you have a problem in the engine wiring harness, interior wiring harness, cross body wiring harness, or overhead wiring harness.