3.
Monitor items related to "A/C" on Current Data
A/C compressor raises pressure to condense the evaporated refrigerant at evaporator in A/C system more easily. Without A/C signal, A/C compressor does not operate but with ON signal, PCU activates A/C compressor relay. With the relay activation, A/C compressor turns on using the power of the engine.
PCM monitors inputted voltage through A/C compressor relay. Checking voltage every 10 sec. under detecting condition, if the voltage lower than the specified value is detected for more than 5 sec., PCM sets P0646.
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Detects circuit short to low voltage | ● Poor connection ● Open or short to ground in A/C relay circuit ● Faulty A/C relay ● Faulty PCM | |||||
Enable Conditions | ● After 0.5 sec under conditions below ● No DTC exists ● Engine works ● 11V ≤ Battery voltage ≤ 16V | ||||||
Threshold value | ● Open or short to ground | ||||||
Diagnosis Time | ● Continuous (More than 5 seconds failure for every 10 seconds test) | ||||||
MIL On Condition | ● DTC only (NO MIL ON) | ||||||
Coil Resistance |
70Ω ~ 120Ω |
Ignition "OFF"
Connect Scantool and Engine "ON"
Monitor items related to "A/C" on Current Data
Are those related current data displayed correctly ?
▶ Fault is intermittent caused by poor contact in Sensor’s and/or PCM’s connector or was repairedand PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection,bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and goto "Verification of Vehicle Repair" procedure
▶ Go to "Terminal and Connector Inspection" procedure.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to " Power Circuit Inspection " procedure.
Check voltage
IG "OFF".
Disconnect A/C relay connector.
IG "ON" and ENG "OFF"
Measure the voltage between terminal 2 of A/C relay harness connector and chassis ground.
Measure the voltage between terminal 4 of A/C relay harness connector and chassis ground.
Specification : B+
Is the measured voltage normal?
▶ Go to "Control circuit inspection" procedure.
▶ Check the fuse between Battery and A/C relay.
▶ Check Chassis ground 1 and 2 for looseness.
▶ Repair Open or Short to ground in power circuit and go to "Verification of Vehicle Repair" procedure.
Check short in harness
IG "OFF".
Disconnect A/C relay and PCM connector.
Measure the resistance between terminal 3 of A/C relay harness connector and chassis ground.
Specification : Infinite
Is the measured resistance within specification ?
▶ Go to "Check open in harness" as follows.
▶ Repair Short in Coil control harness and go to "Verification of Vehicle Repair" procedure.
Check open in harness
IG "OFF".
Disconnect A/C relay and PCM connector.
Measure the resistance between terminal 3 of A/C relay harness connector and terminal 64 of PCM harness connector.
Specification : Approx. below 1Ω
Is the measured resistance within specification ?
▶ Go to "Component inspection" procedure.
▶ Repair Open in Coil control harness and go to "Verification of Vehicle Repair" procedure.
Check A/C relay
IG "OFF".
Disconnect A/C relay.
Measure the resistance between terminal 2 and 3 of A/C relay.
Measure the resistance between terminal 1 and 4 of A/C relay.
Terminal | Power approval |
1~4 | NO |
2~3 | YES (약 70Ω ~ 120Ω) |
Is the measured resistance within specification ?
▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
▶ Substitute with a known - good A/C relay and check for proper operation. If the problem is corrected, replace A/C relay and go to "Verification of Vehicle Repair" procedure.
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. After testing PCM on the vehicle, use this function to reuse the PCM on the others
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
