M/T

BU: DTC 1121 - NEUTRAL POSITION SWITCH CIRCUIT LOW INPUT [MT VEHICLES]

DTC DETECTING CONDITION:
- Two consecutive driving cycles with fault

TROUBLE SYMPTOM:
- Erroneous idling

CAUTION: After repair or replacement of faulty parts, conduct CLEAR MEMORY and INSPECTION MODES. Clearing Diagnostic Trouble Codes





WIRING DIAGRAM

10BU1: CHECK INPUT SIGNAL FOR ECM.
1) Turn ignition switch to ON.

Connector & Terminal (B135) No.26 (+) - Chassis Ground (-):

2) Measure voltage between ECM and chassis ground.

CHECK: Is the voltage between 4.5 and 5.5 V in neutral position?

YES: Go to step 10BU2.

NO: Go to step 10BU4.

10BU2: CHECK INPUT SIGNAL FOR ECM.

Connector & Terminal (B135) No.26 (+) - Chassis Ground (-):

Measure voltage between ECM and chassis ground.

CHECK: Is the voltage less than 1 V in other positions?

YES: Go to step 10BU3.

NO: Go to step 10BU4.

10BU3: CHECK POOR CONTACT.
Check poor contact in ECM connector.

CHECK: Is there poor contact in ECM connector?

YES: Repair poor contact in ECM connector.

NO: Contact with Subaru of America (SOA) service.

NOTE:
Inspection by Subaru of America's DTM is required, because probable cause is deterioration of multiple parts.

10BU4: CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR.
1) Turn ignition switch to OFF.

Connector & Terminal (B135) No.26 (+) - Chassis Ground (-):

2) Measure voltage between ECM and chassis ground.

CHECK: Is the voltage more than 10 V?

YES: Repair battery short circuit in harness between ECM and transmission harness connector.

NO: Go to step 10BU5.

10BU5: CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR.
1) Turn ignition switch to ON.

Connector & Terminal (B135) No.26 (+) - Chassis Ground (-):

2) Measure voltage between ECM and chassis ground.

CHECK: Is the voltage more than 10 V?

YES: Repair battery short circuit in harness between ECM and transmission harness connector.

NO: Go to step 10BU6.

10BU6: CHECK NEUTRAL POSITION SWITCH.

Connector & Terminal (T2) No.1 - No.2:

Measure resistance between transmission harness connector terminals.

CHECK: Is the resistance less than 1 Ohm in other positions?

YES: Go to step 10BU7.

NO: Repair open circuit in transmission harness or replace neutral position switch.

10BU7: CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR.
1) Disconnect connector from ECM.

Connector & Terminal(B135) No.26 - (B25) No.1:

2) Measure resistance of harness between ECM and transmission harness connector.

CHECK: Is the resistance less than 1 Ohm?

YES: Go to step 10BU8.

NO: Repair open circuit in harness between ECM and transmission harness connector.

10BU8: CHECK HARNESS BETWEEN ECM AND NEUTRAL POSITION SWITCH CONNECTOR.

Connector & Terminal(B25) No.2 - Engine Ground:

Measure resistance of harness between transmission harness connector and engine ground.

CHECK: Is the resistance less than 10 V?

YES: Go to step 10BU9.

NO: Repair harness and connector.

NOTE:
In this case repair the following:
- Open circuit in harness between transmission harness connector and engine grounding terminal
- Poor contact in coupling connector (B21)

10BU9: CHECK POOR CONTACT.
Check poor contact in transmission harness connector.

CHECK: Is there poor contact in transmission harness connector?

YES: Repair poor contact in transmission harness connector.

NO: Contact with Subaru of America (SOA) service.

NOTE:
Inspection by Subaru of America's DTM is required, because probable cause is deterioration of multiple parts.