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Inspection Procedure 11: ECM Power Supply, MFI Relay, Ignition Switch-IG1 System
 
 
 
 
CIRCUIT OPERATION
  • The MFI relay and ignition relay are built into the IPDM E/R.
  • ECM connector terminal number 95 applies current to the MFI relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
  • When the MFI relay is turned ON, the 12V battery positive voltage will be supplied from the MFI relay connector terminal to the ECM connector terminal number 79.
  • IPDM E/R operates the ignition relay when it receives an ignition ON signal from BCM via CAN communication.
  • When the ignition relay is turned ON, the 12V battery positive voltage will be supplied from the ignition relay connector terminal to the ECM connector terminal number 84
  • A 12V battery positive voltage is constantly supplied to the ECM connector terminal number 100 as the backup power.
 
 
COMMENT
When the power supply mode of electric motor switch ON signal is input into the ECM, the ECM turns ON the MFI relay. This causes 12V battery voltage to be supplied to the ECM.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • 12V battery failed.
  • IPDM E/R failed.
  • Ignition relay failed.
  • MFI relay failed.
  • Open or shorted ignition relay control circuit, harness damage or connector damage.
  • Open or shorted MFI relay control circuit, harness damage or connector damage.
  • Open or shorted power supply circuit, harness damage or connector damage.
  • Open or shorted battery backup line, harness damage or connector damage.
  • ECM failed.
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
1.STEP 1. Check the 12V battery.
Check 12V battery (Refer to ELECTRICAL & POWER CONTROL, Power Supply, Ground & Circuit Element – Basic Inspection – Battery Inspection – Work Flow Work Flow ).
Q: Is the check result normal?
Replace the 12V battery (Refer to ELECTRICAL & POWER CONTROL, Power Supply, Ground & Circuit Element – Removal and Installation – Battery Removal and Installation ).
 
2.STEP 2. Using scan tool (M.U.T.-III SE), read the other system DTC.
Use scan tool (M.U.T.-III SE) to check and see if a DTC is set in the IPDM E/R [Refer to ELECTRICAL & POWER CONTROL, Power Control System – IPDM E/R – System Description – Diagnosis System (IPDM E/R) M.U.T.-III SE Function (IPDM E/R)].
Q: Is any DTC set in the IPDM E/R?
Perform troubleshooting of IPDM E/R system (Refer to ELECTRICAL & POWER CONTROL, Power Control System – IPDM E/R – System Description – Diagnosis System (IPDM E/R) M.U.T.-III SE Function (IPDM E/R)).
 
3.STEP 3.Perform voltage measurement at ECM connector terminal number 9.
  • Disconnect connector, and measure at harness side.
  • Voltage between ECM connector terminal number 95 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
Repair the wiring harness between IPDM E/R connector terminal number 93 and ECM connector terminal number 95.
 
4.STEP 4.Perform voltage measurement at ECM connector terminal number 79.
  • Disconnect connector, and measure at harness side.
  • Short-circuit the ECM connector terminal number 95 to the ground.
  • Voltage between ECM connector terminal number 79 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
 
5.STEP 5. Check of open circuit and short circuit in wiring harness between IPDM E/R connector terminal number 73 and ECM connector terminal number 79.
Q: Is the check result normal?
Repair the wiring harness between IPDM E/R connector terminal number 93 and ECM connector terminal number 95.
Repair or replace the connector, or repair the damaged harness wire.
 
6.STEP 6. Check of damage in wiring harness between IPDM E/R connector terminal number 73 and ECM connector terminal number 79.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
7.STEP 7. Perform voltage measurement at ECM connector terminal number 84.
  • Disconnect connector, and measure at harness side.
  • Power supply mode of electric motor switch: ON
  • Voltage between ECM connector terminal number 84 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
Repair the wiring harness between IPDM E/R connector terminal number 19 and ECM connector terminal number 84.
 
8.STEP 8. Check of damage in wiring harness between IPDM E/R connector terminal number 19 and ECM connector terminal number 84.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
9.STEP 9. Perform voltage measurement at ECM connector terminal number 100.
  • Disconnect connector, and measure at harness side.
  • Voltage between ECM connector terminal number 100 and ground.
OK: 12V battery positive voltage
Q: Is the check result normal?
Repair the wiring harness between IPDM E/R connector terminal number 44 and ECM connector terminal number 100.
 
10.STEP 10. Check of damage in wiring harness between IPDM E/R connector terminal number 44 and ECM connector terminal number 100.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
11.STEP 11. Check of open circuit and damage in ground lines between ECM connector terminal number 61 and ground, and between ECM connector terminal number 69 and ground.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
12.STEP 12. Check the malfunction symptoms.
Q: Does the malfunction symptom persist?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).