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 and P0445.
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System reaction to a fault:
OK report:
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On condition that 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-relayed 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's fuel requirement has been 25 % lower than that calculated by the control module on the basis of information from the mass air flow sensor.
Fault diagnosis first determines if 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 air leaks between the compressor and throttle and then change the mass air flow sensor.
If the air mass 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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Diagnostic status for the diagnosis.
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Short term fuel trim, in %.
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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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Airmass deviation from calculated, in %.
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See also description of read values in
Menu "Read Values"
for more information.
