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 ...

Dtc p015b a/f / o2 sensor delayed response - lean to rich bank 1 sensor 1

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 ...

Other materials:

Preparation tool
1. SPECIAL TOOLILLUSTRATIONTOOL NUMBERDESCRIPTIONREMARKS18471AA000FUEL PIPE ADAPTERUsed for draining fuel.42099AE000QUICK CONNECTOR RELEASEUsed for removing the quick connector of the fuel delivery tube.18460AA050CHECK BOARDUsed for inspecting the fuel system. — (Newly adopted tool)SUBARU SELECT M ...