CHERY·A21 SERVICE MANUAL ENGINE EFI SYSTEM
55
DTC: P0646 Much lower voltage of air conditioner compressor relay control circuit
No. Operating steps Result Follow up steps
1
Connect the diagnostic tester and commutator, put the
ignition switch to “OFF”.
Next step
Yes To step No.4
2
Take off air conditioner compressor relay; put ignition
switch to “ON”; check the voltage value between relay
power supply ends that relay pin No.30, No.85 and
power cathode and observe if it is around 12V.
No Next step
Yes
Repair or
replace cable
3
Check if there is open circuit or short circuit to ground of
the relay power supplying ends circuit.
No To step No.2
Yes Replace relay
4
Check the voltage value by the multimeter between air
conditioner compressor relay control ends that is relay
pin No.86 and power cathode and observe if it is around
3.7V.
No Next step
Yes
Repair or
replace cable5
Check if there is short circuit to ground between the
circuit of air conditioner compressor relay control ends
that is relay pin No.86 and ECU pin No.70.
No Diagnosis help
DTC: P0647 Much higher voltage of air conditioner compressor relay control circuit
No. Operating steps Result
Follow up
steps
1
Connect the diagnostic tester and commutator, put the
ignition switch to “OFF”.
Next step
Yes To step No.4
2
Take off air conditioner compressor relay; put ignition
switch to “ON”; check the voltage value between relay
power supply ends that relay pin No.30, No.85 and
power cathode and observe if it is around 12V.
No Next step
Yes
Repair or
replace cable
3
Check if there is open circuit or short circuit to ground of
the relay power supplying ends circuit.
No To step No.2
Yes Replace relay
4
Check the voltage value by the multimeter between air
conditioner compressor relay control ends that is relay
pin No.86 and power cathode and observe if it is around
3.7V.
No Next step
Yes
Repair or
replace cable5
Check if there is short circuit to power supply between
the circuit of air conditioner compressor relay control
ends that is relay pin No.86 and ECU pin No.70.
No
Diagnosis
help
