ENGINE GENERAL INFORMATION AND DIAGNOSIS (G16/J20 ENGINES) 6-83
TROUBLESHOOTING (DTC P0171/P0172)
Step Action Yes No
1Was “Engine Diag. Flow Table” performed? Go to Step 2. Go to “Engine Diag. Flow
Ta bl e ”.
2 Is there DTC(s) other than “DTC P0171/
P0172”?
Go to applicable “DTC
Flow Table”.
Go to Step 3.
3 Check intake system and exhaust system for
leakage.
Are intake system and exhaust system in good
condition?
Go to Step 4. Repair or replace.
4 Check fuel pressure referring to “TABLE B-3” in
this section.
Is check result satisfactory?
Go to Step 5. Repair or replace.
5 Check fuel injectors referring to “Fuel Injector”
in Section 6E1.
Is check result satisfactory?
Go to Step 6. Faulty injector(s).
6 Check fuel level sensor referring to “DTC P0460
Diag. Flow Table” in this section.
Is check result satisfactory?
Go to Step 7. Faulty fuel level sensor or
its circuit.
7 Check MAF sensor for performance referring to
“DTC P0100 Diag. Flow Table” in this section.
Is check result satisfactory?
Go to Step 8. Faulty MAF sensor or its
circuit.
8 Check ECT sensor referring to “Engine Coolant
Temperature Sensor (ECT Sensor)” in Section
6E1.
Is check result satisfactory?
Go to Step 9. Faulty ECT sensor.
9 Check HO2S-1 referring to “DTC P0131/P0132
Diag. Flow Table” in this section.
Is check result satisfactory?
Substitute a known-good
ECM (PCM) and recheck.
Faulty HO2S-1.
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