P0172
Read the instructions below then
start the fault diagnostic procedure.
Symptom: CHECK ENGINE.
Engine may stop after starting, uneven running and misfiring.
Long Term Fuel Trim Multiplicative. Min Value, Air/Fuel too Rich.
Fault symptoms
|
•
|
Engine may stop after starting, uneven running and misfiring.
|
On-Board Diagnostics
Type of diagnosis:
|
-
|
Continuous. But interrupted when fault criteria fulfilled and will not restart until next driving cycle.
|
Enable criteria:
|
-
|
The engine is running and the closed loop is active. A multiplicative and an additive adaptation have been done.
|
Fault criteria:
|
-
|
Multiplicative adaptation below -25%.
|
Dependents:
|
-
|
P0116, P0117, P0118, P0131, P0132, P0134, P0444 and P0445.
|
System reaction to a fault:
OK report:
|
-
|
Provided the fault criteria is not fulfilled during the driving cycle the OK report occurs at ignition off before the engine stops. 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.
|
Fault handling:
(See “Fault diagnosis, general” for more information.)
Diagnostic help
Under partial load, the engine fuel requirement is 25 % lower than that computed 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:
|
•
|
Diagnostic status for the diagnosis.
|
|
•
|
Multiplicative adaptation, unit %
|
|
•
|
Short term fuel trim, unit %.
|
|
•
|
Purge adaptation, unit %.
|
|
•
|
Airmass deviation from calculated, in %.
|
See also the description of test values under ”Fault diagnosis, general” for more information.
