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 below 11V, PCM sets P0562. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till cosecutive 2 driving cycle.
Item | Detecting Condition | Possible cause | |
DTC Strategy | ● Voltage too low | ● Poor connection ● Open in power circuit ● Faulty charging system ● Faulty main relay ● Faulty PCM | |
Enable Conditions | ● Engine works ● 11V ≤ Battery voltage ≤ 16V | ||
Thresh old value | ● System voltage〈 11V | ||
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 open in harness" procedure.
▶ Check the fuse between battery and main relay.
▶ Repair Open or Short to ground in power circuit and go to "Verification of Vehicle Repair" procedure
Check open in harness
Key "OFF".
Disconnect main relay and PCM connector.
Measure the resistance between terminal 3 of main relay harness connector and terminals 38,40 of PCM connector.
Specification : Approx. below 1Ω
Is the measured resistance within specification ?
▶ Go to "Check short in harness" procedure.
▶ Repair open in harness and go to "Verification of Vehicle Repair" procedure .
Check short in harness
Key "OFF".
Disconnect main relay and PCM connector.
Measure the resistance between terminal 3 of main relay harness connector and chassis ground.
Specification : Infinite
Is the measured resistance within specification ?
▶ Go to "Control circuit inspection" procedure.
▶ Repair short in harness and go to "Verification of Vehicle Repair" procedure.
Check short in harness
Key "OFF".
Disconnect main relay and PCM connector.
Measure the resistance between terminal 4 of main relay harness connector and chasses ground.
Specification : Infinite
Is the measured resistance within specification ?
▶ Go to "Check open in harness" procedure.
▶ Repair short in control harness and go to "Verification of Vehicle Repair" procedure.
Check open in harness
Key "OFF".
Disconnect main relay and PCM connector.
Measure the resistance between terminal 4 of main relay harness connector and terminal 43 of PCM connector.
Specification : Approx. below 1Ω
Is the measured resistance within specification ?
▶ Go to "Ground circuit inspection" procedure.
▶ Repair Open in control harness and go to "Verification of Vehicle Repair" procedure.
Open in circuit inspection
Key "OFF".
Disconnect PCM connector.
Measure the resistance between terminals 35,36 of PCM(C144-B) connector and chassis ground.
Measure the resistance between terminals 37,38,39 of PCM(C144-B) connector and chassis ground.
Specification : Approx. blow 1Ω
Is the measured resistance within specification ?
▶ Go to "System inspection" procedure.
▶ Repair Open in control 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.
▶ In case terminal 2 : Repair MIL circuit, MIL resistor or Open in circuit and go to "Verification of Vehicle Repair" procedure.
▶ In case terminal 3 : Repair the fuse(30A IG2) between battery and Ignition switch, the fuse(10A IG3) between Ignition switch and alternator or Open in 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 ?
▶ 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 Main relay and check for proper operation. If the problem is corrected, replace Main 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.
