11. DTC: P0171, Air Fuel Ratio Closed Loop Control Self-adaptation Upper Limit Break (see
Table (1-24)
(Note: If the DTC related to intake air pressure sensor, canister control valve, oxygen sensor is
produced, please remove these troubles at first, and then go to the following steps.)
Table 1-24
S/N Operation Test Results Actions
1
Connect the diagnostic instrument and adapter, and turn the
ignition switch to ON.
Next step
Yes Next step
2
Start the engine, and keep idle speed until the coolant reaches
the normal temperature.
Check the “oxygen sensor voltage” on the diagnostic
instrument. At this moment, does it keeps around 100mV for a
long time under certain working conditions?
No Diagnosis help
Yes Next step
3
Connect the fuel pressure gauge to the intake end of the fuel
system. Check if the fuel pressure keeps around 380kPa.
No
Check and repair fuel
system
Yes
Repair or replace
harness
4
Check for short to ground between pin 36#, 18# of the ECU and
pin A# (to the grey connection line of the oxygen sensor), B# (to
the black connection line of the oxygen sensor) of the sensor
with a multimeter.
No Next step
Yes
Check and repair as
per diagnosis
5
A. Check the intake air system for serious leakage;
B. Check if the fuel injector is blocked;
C. Check the spark plug for over-sized gap
D. Check the distribution line for overhigh resistance;
E. Check the valve for over-sized gap.
No Diagnosis help
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