Subaru Crosstrek Service Manual: Dtc p0171 system too lean bank 1

Subaru Crosstrek Service Manual / Engine (diagnostics)(h4do) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0171 system too lean bank 1

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.

Diagnostic method

Fuel system is diagnosed by comparing the target air fuel ratio calculated by ECM with the actual air fuel ratio measured by sensor.

2. EXECUTION CONDITION

Secondary parameters	Execution condition
Main feedback	In operation

3. GENERAL DRIVING CYCLE

Perform the diagnosis continuously at idling or at a constant speed after warming up the engine.

4. DIAGNOSTIC METHOD

Compare the diagnostic value 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
Offset amount of main feedback compensation	≥ Value from Map

Map

Amount of air g/s (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)
Threshold Value	1.33	1.33	1.33	1.33	1.33	1.33	1.33

Amount of air

g/s (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)

Threshold Value

1.33

Time needed for diagnosis: 10 s ? 3 time(s)

Malfunction indicator light illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

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