P0171
Read the instructions below then
start the fault diagnostic procedure.
Symptom: CHECK ENGINE goes on after two driving cycles.
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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CHECK ENGINE goes on after two driving cycles.
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Engine may stop straight after starting, run unevenly and misfire.
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Conditions
The following conditions apply for this DTC.
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Engine running and closed loop active.
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Multiplicative adaptation exceeding 25% for more than 30 s.
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Note
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P1171, P0171 and P1181 can be generated if the input to the sensor is short circuited to ground as there is no diagnosis for it.
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Diagnostic help
The engine's fuel requirement is 25% greater under partial load than that which the control module has calculated using information from the mass air flow sensor.
Fault diagnosis first determines if the pressure sensors indicate about the same value with the ignition ON, as the mass air flow sensor is then compared with the intake air pressure. If the pressure sensors are OK but the mass air flow sensor value is not correct, the mass air flow sensor must be changed. Air leaks will not generate this trouble code.
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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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 test readings,
, for more information.
Checking the wiring
Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits. Observe the multimeter, diagnostic tool or test lamp during the check.
