Suzuki 2000 Grand Vitara SQ625 Service Manual page 70

6-66 ENGINE DIAGNOSIS (G16 / J20 ENGINES)
DTC P0171 FUEL SYSTEM TOO LEAN
DTC P0172 FUEL SYSTEM TOO RICH
SYSTEM DIAGRAM
Refer to Section 6E1.
DTC DETECTING CONDITION AND POSSIBLE CAUSE
DTC DETECTING CONDITION
When running after engine warmed
D Short term fuel trim exceeding 15 % or long term
fuel trim exceeding 20% and total trim exceeding
43 % is detected.
—— Fuel system too lean
D Short term fuel trim less than –11% or long term fuel
trim less than –11% and total trim less than –30%
is detected.
—— Fuel trim too rich
(2 driving cycles detection logic)
DTC CONFIRMATION PROCEDURE
WARNING:
D When performing a road test, select a place where there is no traffic or possibility of a traffic accident
and be very careful during testing to avoid occurrence of an accident.
D Road test should be carried out with 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that the following conditions are satisfied when using this DTC CONFIRMATION PRO-
CEDURE.
D Intake air temp. at start: –8 – 60_C (18 – 140_F)
D Engine coolant temp. at start: –8 – 95_C (18 – 203_F)
D Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
D Intake air temp.: –8_C, 18_F or higher
D Engine coolant temp.: 110_C, 230_F or lower
1) Connect scan tool to DLC with ignition switch OFF.
2) Turn ON ignition switch and clear DTC, pending DTC and freeze frame data by using scan tool and warm up
engine completely.
3) Increase vehicle speed to 50 – 60 km/h (30 – 40 mph).
4) Keep driving above vehicle speed for 3 min. or more.
5) Stop vehicle and check DTC and pending DTC by using scan tool.
POSSIBLE CAUSE
D Vacuum leaks (air inhaling)
D Exhaust gas leakage
D Fuel pressure out of specification
D Heated oxygen sensor malfunction
D EGR system malfunction
D MAF sensor poor performance
D ECT sensor poor performance
D Fuel level sensor