3.
Monitor "Main Relay" parameter on Current Data
The purpose of the System Voltage is to detect an excessively low or high system voltage that may be caused by a malfunctioning charging system.
System Voltage is the ignition voltage potential at the Powertrain Control Module (PCM).PCM measures and compares voltage from ignition key and each relay. With this mechanism, PCM knows if the main relay switch turns on after IG on or if turns OFF after IG off.
During engine running, if battery voltage is above 16V, PCM sets P0563. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till cosecutive 2 driving cycle.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Voltage too high | ● Poor connection ● Short in circuit ● Faulty charging system ● Faulty main relay ● Faulty PCM | |
Enable Conditions | ● Engine works | ||
Thresh old value | ● System voltage 〉16V | ||
Diagnosis Time | ● Continuous | ||
MIL On Condition | ● 2 driving cycles | ||
Coil Resistance | 70Ω ~ 120Ω |
Ignition "OFF"
Connect Scantool and Engine "ON"
Monitor "Main Relay" parameter on Current Data
Is the "Main Relay" parameter displayed correctly ?
▶ Fault is intermittent caused by poor contact in Sensor’s and/or PCM’s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "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.
Power circuit inspection
Key "OFF".
Disconnect the main relay connector.
Key "ON".
Measure the voltage between terminal 2 of main relay harness connector and chassis ground.
Measure the voltage between terminal 5 of main relay harness connector and chassis ground.
Specification : B+
Is the measured voltage within specification ?
▶ Go to "Check short in harness" procedure.
▶ Repair Short in power harness and go to "Verification of Vehicle Repair" procedure.
Check short in harness
Key "ON".
Measure the voltage between terminal 38, 40 of PCM harness terminal and chassis ground.
Specification : B+
Is the measured voltage within specification ?
▶ Go to "System inspection" procedure.
▶ Repair short in power harness and go to "Verification of Vehicle Repair" procedure .
Check Alternator circuit
Key "OFF".
Disconnect alternator connector.
Key "ON".
Measure the voltage between terminal 2 of alternator and chassis gound.
Measure the voltage between terminal 3 of alternator and chassis gound.
Specification : B+
Is the measured voltage within specification?
▶ Go to "Component inspection" procedure.
▶ Repair short in Sensing circuit or MIL circuit and go to "Verification of Vehicle Repair" procedure.
Main relay inspection
Key "OFF".
Disconnect the main relay.
Measure the resistance between terminal 3 and 5 of main relay.
Measure the resistance between terminal 2 and 4 of main relay.
Specification : 70 ~ 120Ω
Terminal | Power approval |
3 ~ 5 | NO |
2 ~ 4 | YES (Approx. 70Ω ~ 120Ω) |
Is the measured resistance within specification ?
▶ Go to "Check Alternator" procedure.
▶ Substitute with a known - good Main relay and check for proper operation. If the problem is corrected, replace Main relay and go to "Verification of Vehicle Repair" procedure.
Check Alternator
Key "OFF".
Check the tension of the belt.
Check Battery terminal and Alternator B+ terminal for looseness, corrosion or damage.
Engine "ON".
Operate electric equipments (Head lamp, Hot wire, etc).
accelerate engine to 2000 RPM and measure the battery voltage.
Specification : Approx. 12.5V ~ 14.5V
Is the measured voltage 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 Alternator and check for proper operation. If the problem is corrected, replace Alternator 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.
