CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM
40
connectors C (white) and D (white) using multimeter,
and observe if it is 2-5Ω when it is 20★.
No Change sensor
Yes Change fuse
4
Check the fuse inside of oxygen sensor heating circuit
and observe if it is blow.
Next step
Yes
Repair or change
cable
5
Check if there is open circuit or short circuit to power
supply between ECU pin No.1, main relay sensor
No.87 and pin C (opposite to oxygen sensor white
connecting line), D (opposite to oxygen sensor white
connecting line) of sensor joint.
No Diagnosis help
DTC: P0171 Closed loop air fuel ratio control self adapting exceeds it maximum 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 100mV 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 Next step
Yes
Repair or replace
cable
4
Check if there is short circuit to ground 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 data
5
A, check if there is a heavy leaking in air intake system
B, check if the injector is jammed
C, check if the clearance of spark plug is too big
D, check if the sub live wire resistance is too big
E, check if the valve clearance is too big etc.
No Diagnosis help
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