PIAGGIO PORTER 1.3 16V 2008, Service Manual

Page: 481 / 892

air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio. Therefore, if the air-fuel ratio
is rich, the fuel injection decreases. Vice versa, if the air-fuel ratio is lean, the fuel injection increases.
Long term fuel trim is a fuel compensation which is detected in a long term period to offset a constant
drift of short term fuel trim with respect to the central value, caused by the intrinsic characteristics of
the vehicle, due to long term use or a variation of the operative environment.
If the total of the short and long term fuel trim exceeds a certain value, and if it turns rich or lean, the
system turns the warning light MIL on to indicate it as a malfunction.
Diagnostic failure code
No.
Diagnostic failure code detection
conditions
Affected area
P0171 If the following conditions are detected
during the execution of the air-fuel return
after warming up the engine:
- Air-fuel too lean: The total of fuel trim
(total of short term and long term fuel trim)
exceeds the set value
- Air intake (pipe loosened)
- Fuel duct pressure
- Injector locking or leakage
- Interrupted or short-circuited wire in the
oxygen sensor circuit.
- Oxygen sensor malfunction
- Manifold absolute pressure sensor
- Engine coolant temperature sensor
- Gas leak in the exhaust system
- Vacuum switching valve for vapour
bleeding
- Engine electronic control unit
P0172 - Air-fuel too rich: (the total of fuel trim is
lower than the set value). (detection logic
with 2 interventions)
IF THE VEHICLE HAS RUN OUT OF FUEL, THE AIR-FUEL RATIO TURNS LEAN, THEREFORE,
THE DIAGNOSTIC FAILURE CODE P0171 IS INDICATED.
READ THE FROZEN IMAGE DATA USING THE DIAGNOSTIC TESTER DS-21 OR OBD II GENERAL
SCANNING DEVICE. AS FROZEN IMAGE DATA RECORD THE ENGINE CONDITIONS AT THE
MOMENT THE DEFECT IS DETECTED, THESE DATA ARE USEFUL TO DETERMINE DURING THE
TROUBLESHOOTING PHASE, IF AT THE MOMENT OF FAILURE CHECKING, THE VEHICLE WAS
WORKING OR AT STANDSTILL, IF THE ENGINE WAS HOT OR NOT, IF THE AIR/FUEL RATIO
WAS LEAN OR RICH ETC.
Functional check
•
With the ignition switch set to OFF, connect the diagnostic tester DS-21 to the Data Link
Connector through the special tool. Set the ignition switch and the tester main switch to ON.
Set the tester to "Continuous monitoring results" of the CARB mode.
•
Start the engine. Warm up the engine for more than five minutes, until the engine cooling
water temperature reaches 90°C or a higher value.
•
Run the vehicle for more than five minutes at a speed of 70 km/h after engaging the 5th gear
or in range D.
•
After one minute the engine is running at idle, press the F1 key on the tester. Check if the
diagnostic failure code P0171/0172 is indicated
PORTER 1.3 16V
Iniection System
IS - 481