Ford Ranger Maintaince And Repair Manual page 250

Oil Pressure Sender
Use the accompanying diagnostic chart to help pinpoint oil pressure sender and oil pressure gauge
malfunctioning.
Oil Pressure Switch
1. To test the oil pressure switch, open the hood and locate the switch.
2. Disconnect the wire from the switch. Attach one end of a jumper wire to the terminal on the end of
the wire, then touch the other end of the jumper wire to a good engine ground (any bare metal engine
surface). Have an assistant observe the instrument gauge cluster while you do this and tell you if the
low oil warning lamp illuminates or not; the low oil warning lamp should illuminate.
1. If the lamp does not illuminate, skip to Step 3.
2. If the lamp does illuminate, replace the switch with a new one.
3. Before jumping to any bad conclusions, try a different area for grounding the jumper wire on the
engine. If the lamp still does not illuminate, touch the jumper wire end to the negative (−) battery
post.
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HOW TO USE THIS BOOK
Oil pressure gauge diagnostic chart
Click to enlarge
TESTING