DTC Troubleshooting

DIAGNOSIS PROCEDURE

Step	Action	YES	NO
1	Was "Engine and Emission Control System Check" performed?	Go to Step 2.	Go to ENGINE AND EMISSION CONTROL SYSTEM CHECK .
2	Is there DTC(s) other than "P0171" and "P0172"?	Go to applicable DTC flow.	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 Check fuel pressure referring to FUEL PRESSURE CHECK . Is check result satisfactory?	Go to Step 5.	Repair or replace.
5	Check fuel injectors Check fuel injectors referring to FUEL INJECTOR INSPECTION . Is check result satisfactory?	Go to Step 6.	Faulty injector(s) or its circuit.
6	Visual inspection Check MAF sensor and air intake system. Objects which block measuring duct and resistor of MAF sensor. Other air flow which does not pass MAF sensor. Are they in good condition?	Go to Step 7.	Repair or replace defective part.
7	Check MAF sensor Check MAF sensor referring to Step 2 and 3 of DTC P0101: MASS AIR FLOW CIRCUIT RANGE / PERFORMANCE . Is check result satisfactory?	Go to Step 8.	Faulty MAF sensor or its circuit.
8	Check ECT sensor Check ECT sensor referring to Step 4 and 5 of DTC P0116: ENGINE COOLANT TEMPERATURE CIRCUIT RANGE / PERFORMANCE . Is check result satisfactory?	Go to Step 9.	Faulty ECT sensor or its circuit.
9	Check HO2S-1 Check HO2S-1 referring to Step 3 of DTC P2A00: O2 SENSOR CIRCUIT RANGE / PERFORMANCE OR DTC P0131 / P0132: O2 SENSOR CIRCUIT LOW / HIGH VOLTAGE (SENSOR- 1) (FOR VEHICLE WITHOUT ORVR) . Is check result satisfactory?	Substitute a known-good ECM and recheck.	Faulty HO2S-1 or its circuit.