Inspection Procedure 34
Ignition Circuit:
Connectors: B-03, B-16, B-21, C-49, C-55 <M/T>, C-50, C-54 <A/T>:
CIRCUIT OPERATION
- The ignition coil is energized by Battery positive voltage from the ignition switch through the ignition failure sensor.
- When the ECM or PCM turns off its internal power transistor, battery positive voltage is applied to the ignition power transistor (terminal 3) inside the ignition coil, causing the ignition power transistor to be turned on.
- If the ignition power transistor is turned on, the primary circuit of the ignition coil is energized by grounding the ignition coil through terminal 2, causing the primary current to flow to the ignition coil.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the ignition coil.
- Malfunction of the ignition power transistor.
- Malfunction of the ignition failure sensor.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM
- Malfunction of the PCM .
DIAGNOSIS
STEP 1. Using an oscilloscope, check the ignition failure sensor.
1. Disconnect ignition failure sensor connector B-03, and connect test harness special tool MB991658 between the disconnected connectors (All terminals should be connected).
2. Connect the oscilloscope probe to the ignition failure sensor-side connector terminal 3.
3. Crank the engine or run it at idle.
4. Inspect the waveform.
- The waveform should show a normal pattern similar to the illustration.
5. Turn the ignition switch to "LOCK" (OFF) position.
If a normal waveform is shown, go to Step 11.
If the waveform does not show a normal pattern, go to Step 2.
STEP 2. Check the ignition failure sensor.
NOTE: An analog-type ohmmeter should be used.
1. Check that the resistance between terminals 3 and 4 is at the standard value.
Standard value: 0.1 ohm or less
If correct, go to Step 3.
If incorrect, replace the ignition failure sensor. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the ignition coil.
1. Check the secondary coil resistance.
2. Measure the resistance between the high-voltage terminals of the ignition coil.
Standard value: 8.5 - 11.5 kohms
3. Check the continuity at the primary coil and ignition power transistor.
NOTE: An analog-type ohmmeter should be used.
NOTE: Connect the negative (-) probe of the ohmmeter to terminal 1.
CAUTION: This test must be performed quickly (in less than 10 seconds) to prevent the coil from burning and ignition power transistor from breaking.
If correct, go to Step 4.
If incorrect, replace the ignition coil.
Then confirm that the malfunction symptom is eliminated.
STEP 4. Check the power supply line at ignition failure sensor connector B-03.
1. Disconnect connector B-03 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 4 and ground.
- Voltage should be approximately 12 volts (battery positive voltage).
4. Turn the ignition switch to "LOCK" (OFF) position.
If within the specifications, go to Step 5.
If not within specification, repair the harness wire and connector between the ignition failure sensor and ignition switch.
Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 5. Check the power supply line at ignition coil connectors B-16 and B-21.
1. Disconnect connectors B-16 and B-21 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 1 and ground.
- Voltage should be approximately 12 volts (battery positive voltage).
4. Turn the ignition switch to "LOCK" (OFF) position.
If within the specifications, go to Step 7.
If not within the specifications, go to Step 6.
STEP 6. Check the harness wire between ignition failure sensor connector B-03 and ignition coil connectors B-16 and B-21.
If the wire between ignition failure sensor connector B-03 and ignition coil connectors B-16 and B-21 is not damaged, repair or replace ignition failure sensor connector B-03. Refer to Harness Connector Inspection.
If the wire between ignition failure sensor connector B-03 and ignition coil connectors B-16 and B-21 is damaged, replace it.
Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the ground line at ignition coil connectors B-16 and B-21.
1. Disconnect connectors B-16 and B-21 and measure at the harness side.
2. Check for continuity between terminal 2 and ground.
- Should be less than 2 ohms.
If less than 2 ohms, go to Step 8.
If open circuit, repair the harness wire between ignition coil connectors B-16 and B-21 and ground.
Then confirm that the malfunction symptom is eliminated.
STEP 8. Check the circuits at ignition coil connectors B-16 and B-21.
1. Disconnect connectors B-16 and B-21 and measure at the harness side.
2. Crank the engine or run it at idle.
3. Measure voltage between terminal 3 and ground.
- Voltage should be between 0.3 and 3.0 volts.
4. Turn the ignition switch to "LOCK" (OFF) position. If within the specifications, repair or replace the ignition coil connector B-16 or B-21.
Refer to Harness Connector Inspection.
If not within the specifications, go to Step 9. Then confirm that the malfunction symptom is eliminated.
STEP 9. Check the harness wire between ignition coil connectors B-16 and B-21 and ECM connector C-49
If the wires between ignition coil connectors B-16, B-21 and ECM connector C-49
If the wires between ignition coil connectors B-16, B-21 and ECM connector C-49
Then confirm that the malfunction symptom is eliminated.
STEP 10. Check harness connector C-49 at the ECM
If harness connector C-49
If harness connector C-49
Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 11. Using an oscilloscope, check the ignition failure sensor.
1. Disconnect ignition failure sensor connector B-03, and connect test harness special tool MB991658 between the disconnected connectors (All terminals should be connected).
2. Connect the oscilloscope probe to ignition failure sensor-side connector terminal 2.
3. Crank the engine and run it at idle.
4. Inspect the waveform.
- The waveform should show a normal pattern similar to the illustration.
5. Turn the ignition switch to "LOCK" (OFF) position.
If a normal waveform is shown, go to Step 12.
If the waveform does not show a normal pattern, go to Step 13.
STEP 12. Check the harness wire between ignition failure sensor connector B-03 and ECM connector C-56
If the wire between ignition failure sensor connector B-03 and ECM connector C-56
Refer to Harness Connector Inspection.
If the wire between ignition failure sensor connector B-03 and ECM connector C-56
Then confirm that the malfunction symptom is eliminated.
STEP 13. Check the circuit at ignition failure sensor connector B-03.
1. Disconnect connector B-03 and measure at the harness side.
2. Turn the ignition switch to "ON" position.
3. Measure the voltage between terminal 2 and ground.
- Voltage should be 4 volts or more.
4. Turn the ignition switch to "LOCK" (OFF) position.
If more than 4 volts, go to Step 14.
If less than 4 volts, go to Step 16.
STEP 14. Check the ground line at the ignition failure sensor connector B-03
1. Disconnect connector B-03 and measure at the harness side.
2. Check the continuity between terminal 1 and ground.
- Should be less than 2 ohms.
If less than 2 ohms, go to Step 15.
If open circuit, repair the harness wire between ignition failure sensor connector B-03 and ground.
Then confirm that the malfunction symptom is eliminated.
STEP 15. Check harness connector B-03 at the ignition failure sensor for damage.
If harness connector B-03 is in good condition, replace the ignition failure sensor.
If harness connector B-03 is damaged, repair or replace it.
Refer to Harness Connector Inspection.
Then confirm that the malfunction symptom is eliminated.
STEP 16. Check the harness wire between ignition failure sensor connector B-03 and ECM connector C-56
If the wire between ignition failure sensor connector B-03 and ECM connector C-56
is not damaged, go to Step 17.
If the wire between ignition failure sensor connector B-03 and ECM connector C-56
Then confirm that the malfunction symptom is eliminated.
STEP 17. Check harness connector C-56 at the ECM
If harness connector C-56
If harness connector C-56
Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.