P0171
Read the instructions below then
start the fault diagnostic procedure.
Symptom: CHECK ENGINE.
Engine may stop straight after starting, run unevenly and misfire.
Long Term Fuel Trim Multiplicative. Max Value, Air/Fuel too Lean.
Fault symptoms
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Engine may stop straight after starting, run unevenly and misfire.
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On-Board Diagnostics
Type of diagnosis:
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Continuous. But interrupted when fault criteria fulfilled and will not restart until next driving cycle.
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Enable criteria:
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Engine running and closed loop active. One multiplicative and one additive adaptation has been performed.
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Fault criteria:
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Multiplicative adaptation exceeds 25 % for more than 30 s.
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Dependents:
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P0116, P0117, P0118, P0131, P0132, P0134, P0444 and P0445.
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System reaction to a fault:
OK report:
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Provided the fault criteria are not fulfilled during the driving cycle the OK report occurs at ignition off before the engine stalls. Two types of OK reports can be given: Type 1: If a DTC is already stored for the diagnosis and similar operating conditions have occurred (coolant temperature above or below 71°C, engine speed 375 rpm and load 10%). Type 2: If there is no DTC stored for the diagnosis or similar operating conditions have not occurred.
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Fault handling:
(See section
Fault handling II, emission-related misfiring or fault in fuel system
for more information.)
Diagnostic help
Under partial load the engine fuel requirement is 25 % higher than that calculated by the control module on the basis of information from the mass air flow sensor.
When carrying out fault diagnosis, first determine whether the pressure sensor readings are approximately the same when the ignition is ON, as the mass air flow sensor is later compared with the intake air pressure. If the pressure sensors are OK but the mass air flow sensor reading is incorrect, the mass air flow sensor must be replaced. Air leaks will not generate this DTC.
If the air quantity is OK, then the fuel supply is checked, i.e. pressure, response, pump flow and finally the injectors.
Functions in the diagnostic tool related to the fault:
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Diagnostic status for the diagnosis.
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Multiplicative Adaptation, unit %
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Purge Adaptation, unit %.
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Air mass deviation from calculated, unit %.
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See also description of readings under
"Read Values" menu
for more information.
