Inspection Procedure 29
INSPECTION PROCEDURE 29Ignition Circuit System
Ignition Circuit
WIRING DIAGRAM and CONNECTOR VIEW
CIRCUIT OPERATION
- The battery positive voltage is applied on the ignition coil by the ignition switch-IG.
- When the ECM turns the power transistor in the ECM "OFF," battery positive voltage is applied on the ignition power transistor (terminal 1) and the ignition power transistor turns "on."
- When the ignition power transistor turns on, the ignition coil's primary circuit is grounded by the ignition power transistor terminal 2.
Then the primary current flows to the ignition coil.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the ignition switch.
- Malfunction of the ignition power transistor.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM.
DIAGNOSIS
STEP 1. Check the power supply line at the ignition coil connector A-66.
(1) Disconnect connector A-66 and measure at the harness side.
(2) Turn the ignition switch "ON."
(3) Connect terminal 2 and ground via a 20-ohms resistor. Measure the current at this time.
- The current should be 0.5 ampere or more.
(4) Turn the ignition switch "OFF."
If within specifications, go to Step 2.
If not within specifications, repair the harness wire and connector between the ignition coil and the ignition switch. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 2. Check the ground line at the ignition power transistor connector A-26.
(1) Disconnect connector A-26 and measure at the harness side.
(2) Check for the continuity between terminal 2 and ground.
- There should be continuity (0 ohms).
If continuity, go to Step 3.
If no continuity, repair the harness wire between the ignition power transistor connector A-26 and ground. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the ignition coil.
Refer to Ignition System.
If correct, go to Step 4.
If incorrect, replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
STEP 4. Check the ignition power transistor.
Refer to Ignition System.
If correct, go to Step 5.
If incorrect, replace the ignition power transistor. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check the power supply line at the ignition power transistor connector A-26.
(1) Disconnect connector A-26 and measure at the harness side.
(2) Turn the ignition switch "ON."
(3) Connect terminal 3 and ground via a 20-ohms resistor. Measure the current at this time.
- The current should be 0.5 ampere or more.
(4) Turn the ignition switch "OFF."
If not within specifications, go to Step 6. If within specifications, go to Step 7.
STEP 6. Check the harness wire between the ignition coil connector A-66 and the ignition power transistor connector A-26.
If the wire between the ignition coil connector A-66 and the ignition power transistor connector A-26 is damaged, repair it.
If the wire between the ignition coil connector A-66 and the ignition power transistor connector A-26 is not damaged, repair or replace the ignition coil connector A-66. Refer to Harness Connector Inspection.
Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the circuit at the ignition power transistor connector A-26.
(1) Disconnect connector A-26 and measure at the harness side.
(2) Crank the engine.
(3) Measure voltage between terminal 1 and ground.
- Voltage should be between 2 and 6 volts. If not within specifications, go to Step 8.
If within specifications, go to Step 10.
STEP 8. Check the harness wire between the ignition power transistor connector A-26 (terminal 1) and the ECM connector C-51 (terminal 10).
If the wire between the ignition power transistor connector A-26 and the ECM connector C-51 is not damaged, go to Step 9.
If the wire between the ignition power transistor connector A-26 and the ECM connector C-51 is damaged, repair it. Then confirm that the malfunction symptom is eliminated.
STEP 9. Check harness connector C-51 at the ECM for damage.
If harness connector C-51 is damaged, repair or replace it. Refer to Harness Connector Inspection.
If harness connector C-51 is in good condition, replace the ECM.
Then confirm that the malfunction symptom is eliminated.
STEP 10. Check the harness wire between the Ignition power transistor connector A-26 (terminal 3) and the ECM connector C-53 (terminal 31).
NOTE: After inspecting the intermediate connector C-78, inspect the wire. If the intermediate connector C-78 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
If the wire between the ignition power transistor connector A-26 and the ECM connector C-53 is damaged, repair it. Then confirm that the malfunction symptom is eliminated.
If the wire between the ignition power transistor connector A-26 and the ECM connector C-53 is not damaged, go to Step 11.
STEP 11. Check harness connector C-53 at the ECM for damage.
If harness connector C-53 is damaged, repair or replace it. Refer to Harness Connector Inspection.
If harness connector C-53 is in good condition, replace the ECM.
Then confirm that the malfunction symptom is eliminated.