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)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0171 system too lean bank 1

Refer to DTC P0172 for diagnostic procedure. Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0172 SYSTEM TOO RICH BANK 1

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

DTC DETECTING CONDITION:Detected when two consecutive driving cycles with fault occur.TROUBLE SYMPTOM:• Improper idling• Engine stalls.• Poor driving performanceCAUTION:After servici ...

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To help prevent corrosion
Wash the vehicle regularly to prevent corrosion of the body and suspension components. Also, wash the vehicle promptly after driving on any of the following surfaces. roads that have been salted to prevent them from freezing in winter mud, sand, or gravel coastal road ...