P0171
Read the instructions below then
start the fault diagnostic procedure.
Symptom: CHECK ENGINE comes on after two driving cycles.
Engine may stop after starting, uneven running and misfiring.
Long Term Fuel Trim Multiplicative. Max Value, Air/Fuel too Lean.
Fault symptoms
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CHECK ENGINE comes on after two driving cycles.
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Engine may stop after starting, uneven running and misfiring.
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Conditions
The following conditions apply for this DTC.
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Engine running and closed loop control is active.
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Multiplicative adaptation exceeds 25 % for more than 30 s.
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Note
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P1171, P0171 and P1181 may be generated if the heated oxygen sensor input is shorted to ground as there is no diagnosis for this event.
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Diagnostic help
Under partial load the engine's 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 mass air flow is OK, then the fuel supply must be checked, i.e. pressure, pressure response, pump flow and then the injectors.
Diagnostic tool functions related to this fault are:
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Multiplicative adaptation, in %
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Short term fuel trim, in %.
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Purge adaptation, in %.
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Airmass deviation from calculated, in %.
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See also the description of test values under ”Fault diagnosis, general” for more information.
Check the wiring
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Note
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Jiggle the leads and in-line connectors at various points and in different directions to detect any intermittent breaks or short circuits in the wiring. Observe the multimeter, test lamp or diagnostic tool while doing this.
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