DTC P0037 - Ho2S Heater Control Circuit Low (Bank 1 Sensor 2) -

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: HO2S Heater Control Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK GROUND CIRCUIT OF ECM. Turn ignition switch to OFF. Disconnect connector from ECM. Measure resistance of harness between ECM connector and chassis ground. Connector & terminal (B136) No. 5 - Chassis ground: (B136) No. 16 - Chassis ground:	Is the measured value less than 5 Ω?	Go to step 3.	Go to step 2.
2 CHECK CURRENT DATA. Start engine. Read data of rear oxygen sensor heater current using Subaru Select Monitor or general scan tool. NOTE: Subaru Select Monitor For detailed operation procedure, refer to the "READ CURRENT DATA FOR ENGINE". < Ref. to SUBARU SELECT MONITOR . > OBD-II scan tool For detailed operation procedures, refer to the General Scan Tool Instruction Manual.	Is the measured value more than 0.2 A?	Repair connector. NOTE: In this case, repair the following: Poor contact in rear oxygen sensor connector Poor contact in rear oxygen sensor connecting harness connector Poor contact in ECM connector	Go to step 3.
3 CHECK OUTPUT SIGNAL FROM ECM. Start and idle the engine. Measure voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 4 (+) - Chassis ground (-):	Is the measured value less than 1.0 V?	Go to step 6.	Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM. Measure voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 4 (+) - Chassis ground (-):	Is the measured value less than 1.0 V when shaking harness and connector of ECM?	Repair poor contact in ECM connector.	Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM. Disconnect connector from rear oxygen sensor. Measure voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 4 (+) - Chassis ground (-):	Is the measured value less than 1.0 V?	Contact with SOA (distributor) service. NOTE: Inspection by DTM is required, because probable cause is deterioration of multiple parts.	Repair battery short circuit in harness between ECM and rear oxygen sensor connector. After repair, replace ECM. < Ref. to ENGINE CONTROL MODULE . >
6 CHECK POWER SUPPLY TO REAR OXYGEN SENSOR. Turn ignition switch to OFF. Disconnect connector from rear oxygen sensor. Turn ignition switch to ON. Measure voltage between rear oxygen sensor connector and engine ground or chassis ground. Connector & terminal (T6) No. 2 (+) - Chassis ground (-):	Is the measured value more than 10 V?	Go to step 7.	Repair power supply line. NOTE: In this case, repair the following: Open circuit in harness between main relay and rear oxygen sensor connector Poor contact in rear oxygen sensor connector Poor contact in coupling connector
7 CHECK REAR OXYGEN SENSOR. Turn ignition switch to OFF. Measure resistance between rear oxygen sensor connector terminals. Terminals No. 1 - No.2:	Is the measured value less than 30 Ω?	Repair harness and connector. NOTE: In this case, repair the following: Open circuit in harness between rear oxygen sensor and ECM connector Poor contact in rear oxygen sensor connector Poor contact in ECM connector Poor contact in coupling connector	Replace rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >