P1172
Read the instructions below then
start the fault diagnostic procedure.
Symptom: Engine may stop straight after starting, run unevenly and misfire.
Short Term Fuel Trim. Min Value, Air/Fuel too Rich.
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 adaptation has been made. No change in status of brake light switch.
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Fault criteria:
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Closed loop below -25%.
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Dependents:
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P0116, P0117, P0118, P0131, P0132, P0134, P0444, P0445 and P1105.
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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.)
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Type II. CHECK ENGINE does not go on.
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Diagnostic help
At some time, the engine fuel requirement has been 25% lower than calculated by the control module 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, then air leaks between the compressor and the throttle are checked for first and then the mass air flow sensor is changed.
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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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 readings under
"Read Values" menu
for more information.
See
P0172
.
