P0171

DTC P0171 / P0172

DTC Detecting Condition and Trouble Area






Wiring Diagram

Refer to P0031 DTC P0031 / P0032
and P0037 DTC P0037 / P0038 / P0054.

DTC Confirmation Procedure

WARNING:

If you do not select a suitable route and take proper precautions when performing a road test, an accident can occur.

- Select a level road with no traffic to minimize the risk of accident.
- Perform the test extremely carefully.
- Perform the road test using 2 persons, a driver and an assistant.

NOTE:

- If DTCs other than aimed DTC are previously detected in DTC confirmation procedure, be sure to troubleshoot DTC previously detected
- Check to make sure that the following condition is satisfied when using this procedure.

- BARO > 75 kPa (0.8 kgf/cm2, 10.8 psi, 0.75 bar)

1) Start engine and warm up to normal operating temperature.
2) Drive vehicle at 50 - 60 km/h (31 - 37 mile/h) for 3 min. (Keep throttle valve opening constantly in this step.)

DTC Troubleshooting

1.
Was "Engine and Emission Control System Check" performed?
YES -
Go to Step 2.
NO -
Go to Engine and Emission Control System Check Engine and Emission Control System Check.

2. DTC check

Check DTC.

Is there DTC(s) other than P0171 and P0172?
YES -
Go to applicable DTC(s).
NO -
Go to Step 3.

3. Exhaust system and air intake system check

Check exhaust system and air intake system for clogging or leak.

Is it in good condition?
YES -
Go to Step 4.
NO -
Repair or replace defective parts.

4. Fuel system check

Check fuel system. Fuel System Inspection

Is it in good condition?
YES -
Go to Step 5.
NO -
Repair or replace defective parts or wire harness.

5. MAF sensor performance check

Turn OFF ignition switch and connect scan tool to DLC.
Start engine and warm up to normal operating temperature.
Check MAF value using scan tool. (Refer to Scan Tool Data Scan Tool Data
for normal value.)

Is normal value indicated?
YES -
Go to Step 6.
NO -
Repair or replace defective parts or wire harness.

6. ECT sensor circuit check

Check ECT sensor circuit referring to Step 3 of P0116 DTC P0116 / P0125 / P0128.

Are they in good condition?
YES -
Go to Step 7.
NO -
Repair or replace defective wire harness.

7. ECT sensor check

Check ECT sensor. ECT (Engine Coolant Temperature) Sensor Inspection

Is it in good condition?
YES -
Go to Step 8.
NO -
Replace ECT sensor.

8. DTC recheck

Replace A/F sensor. Service and Repair
Perform DTC confirmation procedure and check DTC.

Is DTC P0171 or P0172 still detected?
YES -
Substitute a known-good ECM and recheck.
NO -
End.