CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM
41
DTC: P0172 Closed loop air fuel ratio control self adapting exceeds it minimum limit
(Notice: below diagnosis flow is fit for when air intake pressure sensor failure, canister
control valve failure and oxygen sensor failure are not appeared at the same time; if there are
failures existing at the same time please deal with other failures at first and then do as below.)
No. Operating steps Result Follow up steps
1
Connect the diagnostic tester and commutator, put the
ignition switch to “ON”
Next step
Yes Next step
2
Start the engine and leave it at idle speed until its
coolant temperature reaches to the normal value.
Observe the value changes of “oxygen sensor voltage”
item on diagnostic meter, and the displayed value
keeps around the value of 900mV at some working
conditions.
No Diagnosis help
Yes
Repair or replace
the cable
3
Connect the fuel pressure meter (connection position is
the front end of fuel distributing pipe assembly fuel
intake pipe); start the engine and check the fuel
pressure at idle speed conditions if it is around 260kpa;
take off the vacuum pipe on fuel pressure regulator,
check the pressure and observe if it is around 300kpa.
No
Check and repair
fuel system
Yes
Repair or replace
cable
4
Check if there is short circuit to power supply between
ECU pin No.36, No.18 and pin A (opposite to oxygen
sensor gray connecting line), pin B (opposite to
oxygen sensor black connecting line) of sensor joint.
No Next step
Yes
Repair according
to diagnosis data5
A, check if the injector is leaking
B, check if the exhaust pipe is jammed
C, check if the valve clearance is too small etc.
No Diagnosis help
DTC: P0201 The 1
st
cylinder injector circuit failure
No. Operating steps Result Follow up steps
1
Connect the diagnostic tester and commutator, put the
ignition switch to “ON”
Next step
Yes To step No.4
2
Take off the 1
st
cylinder injector joint from the cable,
check the voltage value between this joint pin No.1
and the power cathode by multimeter and observe if it
is 12V.
No Next step
Yes
Repair or replace
the cable3
Check if there is open circuit or short circuit to ground
between the 1
st
injector joint pin No.1 and main relay.
No Next step
Yes Next step
4
Check the resistance value by multimeter between 1
st
cylinder injector pin No.1 and No.2, and observe if it
is 11-13Ω when it is 20℃.
No Change injector
5 Check the voltage value by multimeter between 1
st
Yes Repair according to
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