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Home >> Subaru >> 2006 >> Legacy GT spec.B >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls - Engine (Diagnostics) (H4SO)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0037 Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)

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: 

CAUTION: After repairing or replacing the defective part, perform the Clear Memory Mode < Ref. to OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to PROCEDURE , Inspection Mode. >.

WIRING DIAGRAM: 

Fig 1: HO2S Heater Control Circuit Low (Bank 1 Sensor 2) - Wiring Diagram
G05017538
DIAGNOSIS PROCEDURE

Step Check Yes No
1 CHECK CURRENT DATA. 
  1. Start the engine.
  2. Read the data of rear oxygen (A/F) sensor heater current using Subaru Select Monitor or general scan tool.
NOTE:
  • Subaru Select Monitor

    For detailed operation procedure, refer to "READ CURRENT DATA FOR ENGINE". < Ref. to SUBARU SELECT MONITOR . >

  • General scan tool

    For detailed operation procedure, refer to the general scan tool operation manual.

 Is the current more than 0.2 A? Repair the connector.
NOTE: In this case, repair the following item:
  • Poor contact of the rear oxygen sensor connector
  • Poor contact in rear oxygen sensor connecting harness connector
  • Poor contact in ECM connector
 Go to step 2. 
2 CHECK OUTPUT SIGNAL OF ECM. 
  1. Start and idle the engine.
  2. Measure the voltage between ECM connector and chassis ground.

    Connector & terminal 

    (B136) No. 4 (+) - Chassis ground (-): 

 Is the voltage less than 1 V? Go to step 5.  Go to step 3. 
3 CHECK OUTPUT SIGNAL OF ECM. 
Measure the voltage between ECM connector and chassis ground.
Connector & terminal 
(B136) No. 4 (+) - Chassis ground (-): 		 Does the voltage change by shaking the ECM harness and connector? Repair the poor contact of ECM connector. Go to step 4. 
4 CHECK OUTPUT SIGNAL OF ECM. 
  1. Disconnect the connector from the rear oxygen sensor.
  2. Measure the voltage between ECM connector and chassis ground.

    Connector & terminal 

    (B136) No. 4 (+) - Chassis ground (-): 

 Is the voltage less than 1 V? Replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . > Repair the battery short circuit of harness between ECM and rear oxygen sensor connector. After repair, replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >
5 CHECK POWER SUPPLY TO REAR OXYGEN SENSOR. 
  1. Turn the ignition switch to OFF.
  2. Disconnect the connector from the rear oxygen sensor.
  3. Turn the ignition switch to ON.
  4. Measure the voltage between rear oxygen sensor connector and engine ground or chassis ground.

    Connector & terminal 

    (E23) No. 2 (+) - Chassis ground (-): 

 Is the voltage more than 10 V? Go to step 6.  Repair the power supply line.
NOTE: In this case, repair the following item:
  • Open circuit of harness between main relay and rear oxygen sensor connector
  • Poor contact of the rear oxygen sensor connector
  • Poor contact of coupling connector
6 CHECK REAR OXYGEN SENSOR. 
  1. Turn the ignition switch to OFF.
  2. Measure the resistance between rear oxygen (A/F) sensor connector terminals.

    Terminals No. 1 - No. 2: 

 Is the resistance less than 30 Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit of harness between rear oxygen sensor and ECM connector
  • Poor contact of the rear oxygen sensor connector
  • Poor contact in ECM connector
  • Poor contact of coupling connector
 Replace the rear oxygen sensor. < Ref. to REAR OXYGEN SENSOR . >
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