Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc u0284 lost communication with active grille shutter module "a"

Subaru Legacy BN/BS (2015-2019) Service Manual / Engine (diagnostics)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc u0284 lost communication with active grille shutter module "a"

DTC DETECTING CONDITION:

Immediately at fault recognition

CAUTION:

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

WIRING DIAGRAM:

Active grille shutter Active Grille Shutter

STEP	CHECK	YES	NO
1.CHECK DTC. Check for DTC. Read Diagnostic Trouble Code (DTC)	Is U0284 displayed in «Present fault»-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC U0284 LOST COMMUNICATION WITH ACTIVE GRILLE SHUTTER MODULE "A"	The circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again. NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2.CHECK FOR ANY OTHER DTC ON DISPLAY.	Is any other DTC displayed for engine control system-	Check the appropriate DTC using the “List of Diagnostic Trouble Code (DTC)”. List of Diagnostic Trouble Code (DTC)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC U0284 LOST COMMUNICATION WITH ACTIVE GRILLE SHUTTER MODULE "A"
3.CHECK HARNESS BETWEEN ECM AND ACTIVE GRILLE SHUTTER CONNECTOR. 1) Turn the ignition switch to OFF. 2) Disconnect the battery. 3) Disconnect the connectors from ECM and active grille shutter. 4) Measure the resistance between active grille shutter connector and chassis ground. Connector & terminal (B63) No. 3 — Chassis ground:	Is the resistance 1 M- or more-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC U0284 LOST COMMUNICATION WITH ACTIVE GRILLE SHUTTER MODULE "A"	Repair the short circuit to ground in harness between ECM and active grille shutter connector.
4.CHECK HARNESS BETWEEN ECM AND ACTIVE GRILLE SHUTTER CONNECTOR. Measure the resistance of harness between ECM and active grille shutter connector. Connector & terminal (B134) No. 55 — (B63) No. 3:	Is the resistance less than 10 --	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC U0284 LOST COMMUNICATION WITH ACTIVE GRILLE SHUTTER MODULE "A"	Repair the harness and connector. NOTE: In this case, repair the following item: • Open circuit of harness between ECM and active grille shutter connector • Poor contact of coupling connector
5.CHECK ACTIVE GRILLE SHUTTER POWER SUPPLY. 1) Connect the battery. 2) Measure the voltage between active grille shutter connector and chassis ground. Connector & terminal (B63) No. 2 (+) — Chassis ground (−):	Is the voltage 9 V or more-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC U0284 LOST COMMUNICATION WITH ACTIVE GRILLE SHUTTER MODULE "A"	Repair the power supply circuit.
6.CHECK HARNESS BETWEEN ACTIVE GRILLE SHUTTER CONNECTOR AND CHASSIS GROUND. Measure the resistance of harness between active grille shutter connector and chassis ground. Connector & terminal (B63) No. 4 — Chassis ground:	Is the resistance less than 10 --	Replace the active grille shutter.	Repair the harness and connector. NOTE: In this case, repair the following item: • Open circuit of harness between active grille shutter connector and chassis ground • Poor contact of coupling connector

1. OUTLINE OF DIAGNOSIS

Detect malfunction of LIN communication.

Judge as NG if LIN communication failure has occurred with the active grille shutter.

2. COMPONENT DESCRIPTION

(Common Specifications)

Communication protocol: LIN 2.0

Communication Speed: 19.20 kbps

3. EXECUTION CONDITION

Secondary Parameters	Execution condition
Battery voltage	≥ 10.9 V

4. GENERAL DRIVING CYCLE

Always perform the diagnosis continuously.

5. DIAGNOSTIC METHOD

Judge as NG when the following conditions are established.

Judgment Value

Malfunction Criteria	Threshold Value
Data from control modules connected to LIN	None

Time Needed for Diagnosis: 3000 ms

Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.

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