12. DTC: P0172, Air Fuel Ratio Closed Loop Control Self-adaptation Bottom Limit Break (see
Table 1-25)
(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 1-25
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 900mV 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 power supply 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 fuel injector for leakage;
B. Check the exhaust pipe for leakage;
C. Check the ignition timing for normal operation;
D. Check the intake valve guide for abrasion;
E. Check if the valve gap is too narrow.
No Diagnosis help
To Next Page
Loading...