Inspection Procedure 33
Ignition Circuit System
CIRCUIT OPERATION
- The ignition coil is energized by Battery positive voltage from the ignition switch through the ignition failure sensor.
- When the ECM
- 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
DIAGNOSIS
STEP 1. Check the ignition failure sensor.
Q: Are there any abnormalities?
YES: Go to Step 2.
NO: Replace the ignition failure sensor. Then confirm that the malfunction symptom is eliminated.
STEP 2. Check the ignition coil.
Q: Are there any abnormalities?
YES: Go to Step 3.
NO: Replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check harness connectors B-03 at ignition failure sensor for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 4.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 4. Using the oscilloscope, check the ignition failure sensor.
1. Disconnect the ignition failure sensor connector B-03, and connect test harness special tool (MB991658) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to the ignition failure sensor side connector terminal 3.
3. Start the engine and run at idle.
4. Check the waveform.
- The waveform should show a pattern similar to the illustration.
5. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the waveform normal?
YES: Go to Step 11.
NO: Go to Step 5.
STEP 5. Check the power supply voltage at ignition failure sensor harness side connector B-03.
1. Disconnect the connectors B-03 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 4 and ground. Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the voltage normal?
YES: Go to Step 6.
NO: Check connectors C-26, C-209 and C-301 at intermediate connectors for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connectors are in good condition, repair harness wire between ignition switch connector C-202 terminal 2 and ignition failure sensor connector B-03 terminal 4 because of open circuit. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check harness connector B-16, B-21 at ignition coil for damage.
Q: Is the harness connector in good condition?
YES: Go to Step 7.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the power supply voltage at ignition coil connectors B-16, B-21.
1. Disconnect the connector B-16, B-21 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 1 and ground.
- Voltage should be battery positive voltage.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the voltage normal?
YES: Go to Step 8.
NO: Repair harness wire between ignition failure connectors B-03 terminal 3 and ignition coil connectors B-16, B-21 terminals 1 because of open circuit. Then confirm that the malfunction symptom is eliminated.
STEP 8. Check the circuit at ignition coil harness side connector B-16, B-21.
1. Disconnect the connectors B-16, B-21 and measure at the harness side.
2. Engine cranking.
3. Measure the voltage between terminal 3 and ground.
- Voltage should be 0.3 and 3.0 volts.
4. Turn the ignition switch to the "LOOK"(OFF) position.
Q: Is the voltage normal?
YES: Repair harness wire or harness damage between ignition coil connector B-16, B-21 terminal 2 and ground because of open circuit or harness damage. Then confirm that the malfunction symptom is eliminated.
NO: Go to Step 9.
STEP 9. Check connector C-109 at ECM
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 10. Check for open circuit between ignition coil connector and ECM connector
a. Check the harness wire between ignition coil connector B-16 terminal 3 and ECM connector C-109 terminal 10
b. Check the harness wire between ignition coil connector B-21 terminal 3 and ECM connector C-109 terminal 23
Q: Is the harness wire in good condition?
YES: Replace the PCM. Then confirm that the malfunction symptom is eliminated.
NO: Repair it. Then confirm that the malfunction symptom is eliminated.
STEP 11. Using the oscilloscope, check the ignition failure sensor.
1. Disconnect the ignition failure sensor connector B-03, and connect test harness special tool (MB991658) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to the ignition failure sensor side connector terminal 2.
3. Start the engine and run at idle.
4. Check the waveform.
- The waveform should show a pattern similar to the illustration.
5. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the waveform normal?
YES: It can be assumed that this malfunction is intermittent.
Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 12.
STEP 12. Check the circuit at ignition failure sensor harness side connector B-03.
1. Disconnect the connectors B-03 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 2 and ground.
- Voltage should be 4 volts or more.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the voltage normal?
YES: Repair harness wire between ignition failure sensor connector B-03 terminal 1 and ground because of open circuit or harness damage. Then confirm that the malfunction symptom is eliminated.
NO: Go to Step 13.
STEP 13. Check connector C-116 at ECM
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
STEP 14. Check for open circuit between ignition failure sensor connector B-03 terminal 2 and ECM connector C-116 terminal 58
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then confirm that the malfunction symptom is eliminated.
NO: Repair it. Then confirm that the malfunction symptom is eliminated.