Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc p0171 system too lean bank 1

Subaru Legacy BN/BS (2015-2019) Service Manual / Engine (diagnostics)(h6do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0171 system too lean bank 1

NOTE:

Refer to DTC P0175 for diagnostic procedure. Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0175 SYSTEM TOO RICH BANK 2

1. OUTLINE OF DIAGNOSIS

Detect fuel system malfunction by the amount of main feedback control.

2. EXECUTION CONDITION

Secondary Parameters	Execution condition
Closed loop control with main feedback	Operation

3. GENERAL DRIVING CYCLE

Perform the diagnosis continuously during the closed loop.

4. DIAGNOSTIC METHOD

Compare the diagnostic value (fsobd) with the threshold value, and if a condition meeting the malfunction criteria listed below continues for 10 s - 3 time(s) or more, judge that there is a fault in the fuel system.

Judgment Value

Malfunction Criteria	Threshold Value
fsobd = (sglmd − tglmda) + faf + flaf	≥ Value from Map
In this case: sglmd = measured lambda
tglmda = target lambda
faf = main feedback compensation coefficient (every 64 milliseconds)
flaf = main feedback learning compensation coefficient

Map

Amount of air (g (oz)/s)	0 (0)	3.2 (0.11)	6.4 (0.23)	9.6 (0.34)	12.8 (0.45)	16 (0.56)	19.2 (0.68)
fsobdL1 (%)	1.33	1.33	1.33	1.33	1.33	1.33	1.33

Time Needed for Diagnosis: 10 s - 3 time(s)

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

Dtc p0172 system too rich bank 1

NOTE:Refer to DTC P0175 for diagnostic procedure. Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0175 SYSTEM TOO RICH BANK 21. OUTLINE OF DIAGNOSISDetect fuel system malfunction by th ...

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NOTE:For the diagnostic procedure, refer to DTC P014C. Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P014C A/F / O2 SENSOR SLOW RESPONSE - RICH TO LEAN BANK 1 SENSOR 11. OUTLINE OF DI ...

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Caution
• Prior to starting work, pay special attention to the following:1. Always wear work clothes, a work cap, and protective shoes. Additionally, wear a helmet, protective goggles, etc. if necessary.2. Protect the vehicle using a seat cover, fender cover, etc.3. Prepare the service tools, clean cl ...