DTC P0851 Park/Neutral Switch Input Circuit Low: Trouble Symptom

WARNING: This page is about a different variant/trim than selected.

Improper idling

CAUTION: After servicing or replacing faulty parts, perform Clear Memory Mode < Ref. to OPERATION , Clear Memory Mode. >, and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. >.

Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) Ref. to the appropriate SYSTEM WIRING diagram article. ENGINE TYPE EJ (WITHOUT PUSH BUTTON START).
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) Ref. to the appropriate SYSTEM WIRING diagram article. ENGINE TYPE EJ (WITH PUSH BUTTON START).

Fig 1: Engine Electrical System - Wiring Diagram (Engine Type EJ)
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK INPUT SIGNAL OF ECM. Turn the ignition switch to ON. Place the shift lever in a position other than neutral. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 35 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Repair the poor contact of ECM connector.	Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR. Turn the ignition switch to OFF. Disconnect the connectors from ECM and neutral position switch. Measure the resistance between ECM connector and chassis ground. Connector & terminal (B136) No. 35 - Chassis ground:	Is the resistance 1 MΩ or more?	Replace the neutral position switch. < Ref. to NEUTRAL POSITION SWITCH . >	Repair the short circuit to ground harness between ECM connector and neutral position switch connector.