6-1-78 ENGINE GENERAL INFORMATION AND DIAGNOSIS (H27 ENGINE)
DTC P0174/P0175 Fuel System Too Lean/Rich (Bank 2)
DTC DETECTING CONDITION AND POSSIBLE CAUSE
DTC CONFIRMATION PROCEDURE
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 pending DTC by using scan tool.
DTC DETECTING CONDITION TROUBLE AREA
When running after engine warmed (2 driving cycle
detection logic).
• Short term fuel trim exceeding 15 % or long term fuel
trim exceeding 20 % and total trim exceeding 43 % is
detected.
– Fuel system too lean
• 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
• Vacuum leaks (air inhaling)
• Exhaust gas leakage
• Fuel pressure out of specification
• Heated oxygen sensor malfunction
• EGR system malfunction
• MAF sensor poor performance
• ECT sensor poor performance
• Fuel level sensor.
WARNING:
• When performing a road test, select a place where there is no traffic or possibility of a traffic acci-
dent and be very careful during testing to avoid occurrence of an accident.
• Road test should be carried out with 2 persons, a driver and a tester, on a level road.
NOTE:
Check to make sure that following conditions are satisfied when using this “DTC CONFIRMATION
PROCEDURE”.
• Intake air temp. at start : – 8 – 60°C (18 – 140°F)
• Engine coolant temp. at start : – 8 – 95°C (18 – 203°F)
• Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg (75 kPa) or more)
• Intake air temp. : – 8°C (18°F) or higher
• Engine coolant temp. : 110°C (230°F) or lower
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