DTC P0851 Neutral Switch Input Circuit Low (Mt Model): Wiring Diagram

Fig 1: Neutral Switch Input Circuit Low (MT Model) - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSIS PROCEDURE CHART

Step	Check	Yes	No
1 CHECK INPUT SIGNAL OF ECM. Turn the ignition switch to ON. Place the shift lever in a position except for neutral. Measure the voltage between ECM and chassis ground. Connector & terminal (B136) No. 31 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Go to step 2.	Go to step 4.
2 CHECK INPUT SIGNAL OF ECM. Place the shift lever in neutral. Measure the voltage between ECM and chassis ground. Connector & terminal (B136) No. 31 (+) - Chassis ground (-):	Is the voltage less than 1 V?	Go to step 3.	Go to step 4.
3 CHECK POOR CONTACT. Check poor contact of ECM connector.	Is there poor contact in ECM connector?	Repair poor contact in ECM connector.	Contact your SOA Service Center. NOTE: The probable cause is considered as the deterioration of multiple parts.
4 CHECK NEUTRAL POSITION SWITCH. Turn the ignition switch to OFF. Disconnect the connector from the transmission harness. Place the shift lever in a position except for neutral. Measure the resistance between transmission harness and connector terminals. Connector & terminal (T9) No. 1 - NO.3:	Is the resistance 1 MΩ or more?	Go to step 5.	Repair the short circuit in transmission harness, or replace the neutral position switch.
5 CHECK NEUTRAL POSITION SWITCH. Place the shift lever in neutral. Measure the resistance between transmission harness connector terminals.	Is the resistance less than 1 Ω?	Go to step 6.	Repair the short circuit in transmission harness, or replace the neutral position switch.
6 CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR. Measure the resistance between ECM and chassis ground. Connector & terminal (B136) No. 31 - Chassis ground:	Is the resistance 1 MΩ or more?	Go to step 7.	Repair the ground short circuit of harness between ECM and transmission harness connector.
7 CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR. Disconnect the connectors from ECM. Measure the resistance of harness between ECM and transmission harness connector. Connector & terminal (B136) No. 31 - (B128) No. 1:	Is the resistance less than 1 Ω?	Go to step 8.	Repair the open circuit of harness between ECM and transmission harness connector.
8 CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR. Measure the resistance of the harness between the ECM and transmission harness connector. Connector & terminal (B128) No. 3 - (B136) No. 6:	Is the resistance less than 5 Ω?	Go to step 9.	Repair the open circuit between the transmission harness connector and ECM.
9 CHECK POOR CONTACT. Check poor contact of transmission harness connector.	Is there poor contact in transmission harness connector?	Repair the poor contact of transmission harness connector.	Contact your SOA Service Center. NOTE: The probable cause is considered as the deterioration of multiple parts.