Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc p0030 a/f / o2 heater control circuit bank 1 sensor 1

Subaru Legacy BN/BS (2015-2019) Service Manual / Engine (diagnostics)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0030 a/f / o2 heater control circuit bank 1 sensor 1

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode Clear Memory Mode > OPERATION, and Inspection Mode Inspection Mode > PROCEDURE.

WIRING DIAGRAM:

• Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM

• Engine Electrical System ENGINE TYPE FB (WITH PUSH BUTTON START) Engine Electrical System > WIRING DIAGRAM

STEP	CHECK	YES	NO
1.CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR. 1) Start and warm up the engine. 2) Turn the ignition switch to OFF. 3) Disconnect the connectors from ECM and front oxygen (A/F) sensor. 4) Measure the resistance of harness between ECM connector and front oxygen (A/F) sensor connector. Connector & terminal (B158) No. 5 — (E24) No. 1: (B158) No. 46 — (E24) No. 3: (B158) No. 33 — (E24) No. 4:	Is the resistance less than 1 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0030 A/F / O2 HEATER CONTROL CIRCUIT BANK 1 SENSOR 1	Repair the open circuit of harness between ECM connector and front oxygen (A/F) sensor connector.
2.CHECK FRONT OXYGEN (A/F) SENSOR. Measure the resistance between front oxygen (A/F) sensor terminals. Terminals No. 1 — No. 2:	Is the resistance 2 — 3 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0030 A/F / O2 HEATER CONTROL CIRCUIT BANK 1 SENSOR 1	Replace the front oxygen (A/F) sensor. Front Oxygen (A/F) Sensor
3.CHECK FOR POOR CONTACT. Check for poor contact of ECM and front oxygen (A/F) sensor connector.	Is there poor contact of ECM or front oxygen (A/F) sensor connector-	Repair the poor contact of ECM or front oxygen (A/F) sensor connector.	Replace the front oxygen (A/F) sensor. Front Oxygen (A/F) Sensor

1. OUTLINE OF DIAGNOSIS

Detect functional errors of the front oxygen (A/F) sensor heater.

Judge as NG when it is determined that the front oxygen (A/F) sensor impedance is large when looking at engine status such as deceleration fuel cut.

2. COMPONENT DESCRIPTION

(1)	Element cover (outer)	(3)	Sensor element	(4)	Sensor housing
(2)	Element cover (inner)

3. EXECUTION CONDITION

Secondary Parameters	Execution condition
Battery voltage	≥ 10.9 V
Front oxygen (A/F) sensor heater control duty	> 17 %
After fuel cut	≥ 20000 ms

4. GENERAL DRIVING CYCLE

Perform the diagnosis continuously when 20000 ms have elapsed since the fuel cut was initiated after starting the heater control.

5. DIAGNOSTIC METHOD

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Judgment Value

Malfunction Criteria	Threshold Value
Front oxygen (A/F) sensor impedance	> 82 -

Time Needed for Diagnosis: 10000 ms

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

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