P1171
Read the instructions below then
start the fault diagnostic procedure.
Symptom: The engine may stop after starting, run unevenly and misfire, or idle speed too fast.
Short Term Fuel Trim. Max Value, Air/Fuel too Lean.
Fault symptoms
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The engine may stop after starting, run unevenly and misfire, or idle speed too fast.
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Conditions
The following conditions apply for this DTC:
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Engine running and a multiplicative adaptation has been carried out during the current driving cycle.
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Closed loop exceeding 25% for more than 20 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
At some time, the engine fuel requirement has been 25% greater than calculated by the control module using information from the mass air flow sensor.
Fault diagnosis first determines whether the pressure sensors show about the same value with the ignition 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 is incorrect then check for air leaks after the throttle and thereafter, change the mass air flow sensor.
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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Additive Adaptation, unit mg/c.
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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.
