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P1172

Read the instructions below then start the fault diagnostic procedure.

Symptom: Engine may stop straight after starting, run unevenly and misfire.

P1172


Short Term Fuel Trim. Min Value, Air/Fuel too Rich.


Fault symptoms


• Engine may stop straight after starting, run unevenly and misfire.


On-Board Diagnostics

Type of diagnosis:


- Continuous. But interrupted when fault criteria fulfilled and will not restart until next driving cycle.


Enable criteria:


- Engine running and closed loop active. One multiplicative adaptation has been made. No change in status of brake light switch.


Fault criteria:


- Closed loop below -25%.


Dependents:


- P0115, P0116, P0117, P0118, P0119, P0131, P0132, P0134, P0444, P0445, P1105 and P1133.


System reaction to a fault:


- None.


OK report:


- Provided fault criteria are not fulfilled during the driving cycle, the OK report will made when the ignition is turned off and before the engine stops. Two other types of OK report can also be made:

Type 1: If a diagnostic trouble code has already been stored for the diagnosis and the same running conditions have occurred (coolant temperature above or below 71°C, engine speed ±375 rpm and load ±10%).

Type 2: If there is no diagnostic trouble code stored for the diagnosis or the same running conditions have not occurred.


Fault handling: (For more information, see .)


- Type II. CHECK ENGINE does not go on.


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:


• Diagnostic status for the diagnosis.

• Closed loop, unit %.

• Multiplicative Adaptation, unit %

• Additive adaptation, unit mg/c.

• Purge Adaptation, unit %.

• Air mass deviation from calculated, unit %.


For more information, see .