[Previous][Next]
Inspection Procedure 13: Ignition circuit system
 
 
 
 
CIRCUIT OPERATION
  • The MFI relay is built into the IPDM E/R.
  • The 12V battery voltage is supplied to each ignition coil connector terminal number 3 from the MFI relay, and each ignition coil connector terminal number 2 is grounded.
  • The 12V battery voltage is supplied to each ignition coil connector terminal number 1 from the ECM connector terminal number 10, 11, 12 and 13.
 
 
COMMENT
  • When the ECM turn the power transistor in the unit to OFF, the 12V battery voltage is applied to the power transistor in the ignition coil, resulting that the power transistor is ON. And, when the ECM turns the power transistor in the unit to ON, the power transistor in the ignition coil will be turned OFF.
  • When the power transistor in the ignition coil is turned to ON with any signal from the ECM, the primary voltage will be applied through the ignition coil. When the power transistor in the ignition coil is turned OFF, the primary current is blocked and high voltage is generated in the secondary coil.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this case:)
  • Ignition coil failed.
  • Spark plug failed.
  • Open or shorted ignition circuit, harness damage or connector damage.
  • ECM failed.
 
 
DIAGNOSIS
1.STEP 1. Visual check of ignition spark.
(1) Remove the spark plug and attach the removed spark plug to the ignition coil (Refer to ENGINE, Engine Electrical – Ignition Coil IGNITION COIL REMOVAL AND INSTALLATION).
(2) Disconnect the fuel injector connectors for all cylinders.
(3) Connect the ignition coil connector.
(4) Ground the ground electrode of the spark plug, and set the vehicle to the continuous idling mode (Refer to GENERAL INFORMATION, General Information – Precautions CONTINUOUS IDLING MODE).
(5) Check that the electrode of the spark plug sparks.
Q: Is the check result normal?
 
2.STEP 2. Check the spark plug.
Check the number 1 cylinder spark plug, number 2 cylinder spark plug, number 3 cylinder spark plug and number 4 cylinder spark plug itself (Refer to ENGINE , Engine Electrical – On-vehicle Service SPARK PLUG CHECK AND CLEANING).
Q: Are the check result normal?
Replace the faulty spark plug (Refer to ENGINE , Engine Electrical – Ignition Coil IGNITION COIL REMOVAL AND INSTALLATION).
 
3.STEP 3. Check the ignition coil.
Check the number 1 cylinder ignition coil, number 2 cylinder ignition coil, number 3 cylinder ignition coil and number 4 cylinder ignition coil itself (Refer to ENGINE , Engine Electrical – On-vehicle Service IGNITION COIL CHECK).
Q: Are the check result normal?
Replace the faulty ignition coil (Refer to ENGINE , Engine Electrical – Ignition Coil IGNITION COIL REMOVAL AND INSTALLATION).
 
4.STEP 4. Perform voltage measurement at each ignition coil connector terminal number 3.
  • Disconnect connector, and measure at harness side.
  • Power supply mode of electric motor switch: ON
  • Voltage between each ignition coil connector terminal number 3 and ground.
OK: 12V battery positive voltage
Is the check result normal?
Repair the wiring harness between IPDM E/R connector terminal number 66 and each ignition coil connector terminal number 3.
 
5.STEP 5. Perform resistance measurement at each ignition coil connector terminal number 2.
  • Disconnect connector, and measure at harness side.
  • Resistance between each ignition coil connector terminal number 2 and ground.
OK: Continuity (2 ohms or less)
Q: Is the check result normal?
Repair the ground line between the each ignition coil connector terminal number 2 and ground.
 
6.STEP 6. Check of open circuit, short circuit and damage in wiring harnesses between number 1 cylinder ignition coil connector terminal number 1 and ECM connector terminal number 10, between number 2 cylinder ignition coil connector terminal number 1 and ECM connector terminal number 11, between number 3 cylinder ignition coil connector terminal number 1 and ECM connector terminal number 12 and between number 4 cylinder ignition coil connector terminal number 1 and ECM connector terminal number 13.
Q: Are the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
7.STEP 7. Check of damage in wiring harness between IPDM E/R connector terminal number 66 and each ignition coil connector terminal number 3.
Q: Is the check result normal?
Repair or replace the connector, or repair the damaged harness wire.
 
8.STEP 8. 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).