Chery A21 2005 Service Manual page 361

CHERY·A21 SERVICE MANUAL
connectors C (white) and D (white) using multimeter,
Check the fuse inside of oxygen sensor heating circuit
4
Check if there is open circuit or short circuit to power
supply between ECU pin No.1, main relay sensor
5
No.87 and pin C (opposite to oxygen sensor white
connecting line), D (opposite to oxygen sensor white
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.
Connect the diagnostic tester and commutator, put the
1
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"
2
item on diagnostic meter, and the displayed value keeps
around the value of 100mV at some working conditions.
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
3
at idle speed conditions if it is around 260kpa; take off
the vacuum pipe on fuel pressure regulator, check the
Check if there is short circuit to ground between ECU
pin No.36, No.18 and pin A (opposite to oxygen sensor
4
gray connecting line), pin B (opposite to oxygen sensor
A, check if there is a heavy leaking in air intake system
5
D, check if the sub live wire resistance is too big
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and observe if it is 2-5Ω when it is 20℃.
and observe if it is blow.
connecting line) of sensor joint.
Operating steps
ignition switch to "ON".
pressure and observe if it is around 300kpa.
black connecting line) of sensor joint.
B, check if the injector is jammed
C, check if the clearance of spark plug is too big
E, check if the valve clearance is too big etc.
38
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ENGINE EFI SYSTEM
No Change sensor
Yes Change fuse
Next step
Repair or change
Yes
cable
No Diagnosis help
Result Follow up steps
Next step
Yes Next step
No Diagnosis help
Repair or replace
Yes
the cable
No Next step
Repair or replace
Yes
cable
No Next step
Repair according
Yes
to diagnosis data
No Diagnosis help