DTC P0866 - TCM Communication circuit high -

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

DTC DETECTING CONDITION:
- Two consecutive driving cycles with malfunction
CAUTION: After repair or replacement of malfunctioning parts, conduct Clear Memory Mode < Ref. to OPERATION , CLEAR MEMORY MODE > and INSPECTION MODE < Ref. to OPERATION , INSPECTION MODE. >
WIRING DIAGRAM:

Fig 1: TCM Communication Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR. Turn ignition switch to ON. Measure voltage between ECM and chassis ground. Connector & terminal (B137) No. 19 (+) - Chassis ground (-):	Is the measured value more than 10 V?	Repair battery short circuit in harness between ECM and TCM connector. After repair, replace ECM. < Ref. to ENGINE CONTROL MODULE . >	Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR. Measure voltage between ECM connector and chassis ground. Connector & terminal (B137) No. 19 (+) - Chassis ground (-):	Is the measured value more than 4 V?	Go to step 5.	Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR. Measure voltage between ECM connector and chassis ground. Connector & terminal (B137) No. 19 (+) - Chassis ground (-):	Is the measured value less than 1 V?	Repair poor contact in ECM connector.	Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM. Measure voltage between ECM and chassis ground. Connector & terminal (B137) No. 19 (+) - Chassis ground (-):	Is the measured value within 1 to 4V?	Even if MIL lights up, the circuit has returned to a normal condition at this time. NOTE: In this case, repair the following: Poor contact in ECM connector Poor contact in TCM connector	Contact with SOA service center. NOTE: Inspection by DTM is required, because probable cause is deterioration of multiple parts.
5 CHECK HARNESS BETWEEN ECM AND TCM CONNECTOR. Measure voltage between TCM and chassis ground. Connector & terminal (B54) No. 4 (+) - Chassis ground (-):	Is the measured value more than 4 V?	Go to step 6.	Repair open circuit in harness between ECM and TCM connector.
6 CHECK POOR CONTACT. Check poor contact in TCM connector.	Is there poor contact in TCM connector?	Repair poor contact in TCM connector.	Check TCM power supply line and grounding line.