DTC P0851 Park/Neutral Switch Input Circuit Low: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

Improper idling

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

1. CHECK SELECT CABLE. 

   Is there any fault in select cable?

   • Yes  : Repair or adjust the select cable. Ref. to CONTROL SYSTEMS>Select Cable .
   • No  : Go to 2. 
2. CHECK INPUT SIGNAL OF ECM. 
   1. Turn the ignition switch to ON.
   2. Place the select lever in other than "P" range and "N" range.
   3. Measure the voltage between ECM and engine ground.

      Connector & terminal 

      (B134) No. 33 (+) - Engine ground (-):

      Is the voltage 10 V or more?

      • Yes  : Repair the poor contact of ECM connector.
      • No  : Go to 3. 
3. CHECK HARNESS BETWEEN ECM AND TRANSMISSION HARNESS CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the transmission harness connector (T3).
   3. Disconnect the connector from ECM.
   4. Measure the resistance between ECM and engine ground.

      Connector & terminal 

      (B134) No. 33 - Engine ground:

      Is the resistance 1 MΩ or more?

      • Yes  : Go to 4. 
      • No  : Repair the ground short circuit of harness between ECM and transmission harness connector.
4. CHECK TRANSMISSION HARNESS CONNECTOR. 
   1. Disconnect the connector from inhibitor switch.
   2. Measure the resistance between transmission harness connector and engine ground.

      Connector & terminal 

   (T3) No. 12 - Engine ground:

   Is the resistance 1 MΩ or more?

   • Yes  : Replace the inhibitor switch. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>Inhibitor Switch .
   • No  : Repair short circuit to ground in harness between transmission harness connector and inhibitor switch connector.