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 multiplicative adaptation has been performed during present driving cycle.
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Closed loop control exceeds 25 % for more than 20 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
At some time, the engine's fuel requirement has been 25 % higher than that computed by the control module on the basis of information from the mass air flow sensor.
Fault diagnosis first determines 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, first check for any air leaks after the throttle and after that, replace the sensor.
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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Short term fuel trim, in %.
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Multiplicative adaptation, in %
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Additive adaptation, in mg/c.
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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 readings under
Menu "Read Values"
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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