Problem: Vehicle had DTC faults: P0335 for crankshaft position sensor, P0642 for sensor reference voltage 1 circuit low and P2122 for APP sensor circuit. The engine also lacked power.
Details: The technician found a wiring diagram included with the P0642 DTC diagnosis chart. All three (3) codes could be set by the sensors residing on the same circuit. The technician tested the circuit to verify a 5-volt reference. The pink/yellow wire was only showing 1.6 volts at the PCM. The technician thought one of the sensors could be shorted so he disconnected all of them – the wire was still reading 1.6 volts. He then disconnected the pink/yellow wire from the PCM – now there was 5 volts coming out of the PCM. Using the wiring diagrams, he located the engine oil pressure sensor that was also powered-up on the same circuit. Once that sensor was disconnected, he finally got 5 volts back at the PCM.
Confirmed Repair: Once the engine oil pressure sensor was replaced, the technician cleared the codes and road tested until all the monitors were complete and the problem was corrected.