Oil Pressure Sensor Circuit Fault, Code 141 (Cummins N14 Celect Plus)

This week in the shop we did some cleanup. Pretty standard stuff, but while looking for a magnet I found this:

Mechanic ingenuity?

Someone had welded a socket to a long piece of all-thread. What the purpose of this tool was I did not learn.

What I did learn, however, was how to read flash codes on a Cummins N14 Celect Plus in the school's International sleeper truck. Courtesy of some quick research on Cummins Quickserve and Google, we ascertained exactly how to read the code flashed on the dash, and found one code, 141. Once again with the help of Google we found this to be an oil pressure sensor circuit fault. So we printed out a component location diagram and went to look:

Oil pressure sensor location. Right under the ECM on the driver's side, mounted in the block.

The actual sensor on the vehicle.

When we checked the sensor, it was unplugged. Mistake from a previous team? Deliberate bugging? Who knows, but once we plugged the sensor back in, the check engine light went out and we were good to go.

Reflection:

Once again we get back to "keep it simple, stupid," the sensor was simply unplugged. However, that might not have been the only problem with it. So what is the next step in the repair process? Verify that the seemingly obvious fix did indeed correct the problem. In our case, it did. But what if there were wiring issues down the line? Then the diagnostic process would continue, with one possible cause (disconnected connector) eliminated. That would have been our next step, had the check engine light stayed illuminated.