1A
DTC P0171 / P0172: Fuel System Too Lean / Rich
DTC Detecting Condition and Trouble Area
DTC detecting condition Trouble area
DTC P0171:
Total fuel trim is higher than 35% or short term fuel trim is higher than 20% for more than 1 min. continuously.
(2 driving cycle detection logic)
DTC P0172:
Total fuel trim is lower than –35% or short term fuel trim is lower than –20% for more than 1 min. continuously.
(2 driving cycle detection logic)
Vacuum leaks
Exhaust gas leakage
Fuel pressure out of specification
Fuel injector malfunction
Heated oxygen sensor-1 malfunction
MAF sensor malfunction
ECT sensor malfunction
DTC Confirmation Procedure
WARNING:
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.
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 Procedure”.
Intake air temperature at engine start: –10 °C (14 °F) to 80 °C (176 °F)
Intake air temperature: –10 °C (14 °F) to 70 °C (158 °F)
Engine coolant temperature: 70 °C (158 °F) to 150 °C (302 °F)
Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
1) With ignition switch turned OFF, connect scan tool.
2) Turn ON ignition switch and clear DTC using scan tool.
3) Start engine and warm up to normal operating temperature.
4) Operate vehicle within freeze frame data condition as noted for 5 min.
5) Stop vehicle and check DTC and pending DTC.
DTC Troubleshooting
Step Action YES NO
1
Was “Engine and Emission Control System Check” performed?
Go to Step 2.
2
Is there DTC(s) other than fuel system (DTC P0171/P0172)?
Go to applicable DTC diag. flow.
Go to Step 3.
3
Intake system and exhaust system for leakage check
Are intake system and exhaust system in good condition?
Go to Step 4.
Repair or replace.
4
Fuel pressure check
1) Check fuel pressure referring to Fuel Pressure Inspection:M13A .
Is check result satisfactory?
Go to Step 5.
Repair or replace.
5
Fuel injectors and its circuit check
1) Check fuel injectors referring to Fuel Injector Inspection:M13A .
Is check result satisfactory?
Go to Step 6.
Faulty injector(s) or its circuit.
6
Visual inspection
1) Check MAF sensor and air intake system.
Objects which block measuring duct and resistor of MAF sensor.
Other air flow which does not pass the MAF sensor.
Are there in good condition?
Go to Step 7.
Repair or replace.
7
MAF sensor for performance check
1) With ignition switch turned OFF, install scan tool.
2) Start engine and warm up to normal operating temperature.
3) Check MAF value using scan tool (Refer to Scan Tool Data:M13A with VVT for normal value.).
Is each value within specified?
Go to Step 8.
8
ECT sensor for performance check
1) Check ECT sensor referring to Step 3 and 4 of DTC P0118: Engine Coolant Temperature Circuit High:M13A with VVT .
Is check result satisfactory?
Go to Step 9.
Faulty ECT sensor or its circuit.
9
HO2S-1 for performance check
Is check result satisfactory?
Substitute a known-good ECM and recheck.
Faulty HO2S-1 or its circuit.
NOTE:
Upon completion of inspection and repair work, perform “DTC Confirmation Procedure” and confirm that the trouble has been corrected.