Inspection Procedure 26: Ignition Circuit System

OPERATION

The battery voltage is applied to the ignition coil (terminal No. 1) from the ignition switch and is earthed to the vehicle body from the ignition coil (terminal No. 2).
A power voltage of 12 V is applied to the ignition coil output terminal (terminal No. 3) from the engine-A/T-ECU (terminal No. 31, No. 32, No. 35 and No. 52).

FUNCTION

When the engine-A/T-ECU makes the power transistor in the unit be in OFF position, the battery voltage in the unit is applied to the power transistor unit, and that makes the power transistor unit be in ON position. The engine-A/T-ECU makes the power transistor in the unit be in ON, and that makes the power transistor unit be in OFF position.
In response to the signal from the engine-A/T-ECU, the power transistor unit is in ON position. The primary current is going to the ignition coil. When the power transistor unit is in OFF position, the primary current is interrupted and high voltage is generated in the secondary coil.

PROBABLE CAUSE

Failed ignition coil
Failed spark plug
Open/short circuit in ignition primary circuit or loose connector contact
Failed engine-A/T-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check spark plug.

Q. Is the check result normal?

	Go to Step 2 .

	Replace spark plug.

STEP 2. Connector check: B-02, B-03, B-04 and B-05 ignition coil connectors

Q. Is the check result normal?

Go to Step 3 .

Repair or replace.

STEP 3. Check ignition coil itself.

Check ignition coil itself (Refer to GROUP 16 - Ignition System - On-vehicle Service - Ignition coil check ).

Q. Is the check result normal?

	Go to Step 4 .

	Replace ignition coil.

STEP 4. Perform voltage measurement at B-02, B-03, B-04 and B-05 ignition coil connectors.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal No. 1 and earth.

OK: System voltage

Q. Is the check result normal?

Go to Step 6 .

Go to Step 5 .

STEP 5. Connector check: C-307 ignition switch connector

Q. Is the check result normal?

Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-02 (terminal No. 1) No. 1 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-03 (terminal No. 1) No. 2 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-04 (terminal No. 1) No. 3 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-05 (terminal No. 1) No. 4 ignition coil connector

Check power supply line for open/short circuit.

Repair or replace.

STEP 6. Perform voltage measurement at B-02, B-03, B-04 and B-05 ignition coil connectors.

Disconnect connector, and measure at harness side.
Engine: Cranking
Voltage between terminal No. 3 and earth.

OK: 0.1 - 2.0 V

Q. Is the check result normal?

Go to Step 11 .

Go to Step 7 .

STEP 7. Connector check: C-111 engine-A/T-ECU connector

Q. Is the check result normal?

Go to Step 8 .

Repair or replace.

STEP 8. Perform voltage measurement at C-111 engine-A/T-ECU.

Measure engine-A/T-ECU terminal voltage.
Disconnect B-02, B-03, B-04 and B-05 ignition coil connectors.
Engine: Cranking

Voltage between terminal No. 31 and earth (No. 1 Ignition coil).
Voltage between terminal No. 32 and earth (No. 2 Ignition coil).
Voltage between terminal No. 35 and earth (No. 3 Ignition coil).
Voltage between terminal No. 52 and earth (No. 4 Ignition coil).

OK: 0.1 - 2.0 V

Q. Is the check result normal?

Check and repair harness between B-02 (terminal No. 3) No. 1 ignition coil connector and C-111 (terminal No. 31) engine-A/T-ECU connector.
Check and repair harness between B-03 (terminal No. 3) No. 2 ignition coil connector and C-111 (terminal No. 32) engine-A/T-ECU connector.
Check and repair harness between B-04 (terminal No. 3) No. 3 ignition coil connector and C-111 (terminal No. 35) engine-A/T-ECU connector.
Check and repair harness between B-05 (terminal No. 3) No. 4 ignition coil connector and C-111 (terminal No. 52) engine-A/T-ECU connector.

Check output line for open circuit.

Go to Step 9 .

STEP 9. Check harness between ignition coil connector and engine-A/T-ECU connector.

Check and repair harness between B-02 (terminal No. 3) No. 1 ignition coil connector and C-111 (terminal No. 31) engine-A/T-ECU connector.
Check and repair harness between B-03 (terminal No. 3) No. 2 ignition coil connector and C-111 (terminal No. 32) engine-A/T-ECU connector.
Check and repair harness between B-04 (terminal No. 3) No. 3 ignition coil connector and C-111 (terminal No. 35) engine-A/T-ECU connector.
Check and repair harness between B-05 (terminal No. 3) No. 4 ignition coil connector and C-111 (terminal No. 52) engine-A/T-ECU connector.

Check output line for short circuit.

Q. Is the check result normal?

Go to Step 10 .

Repair.

STEP 10. Check the trouble symptom.

Q. Does the trouble symptom persist?

	Replace engine-A/T-ECU.

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points ).

STEP 11. Perform resistance measurement at B-02, B-03, B-04 and B-05 ignition coil connectors.

Disconnect connector, and measure at harness side.
Resistance between terminal No. 2 and earth.

OK: 2 Ω or less

Q. Is the check result normal?

Go to Step 12 .

Check and repair harness between B-02 (terminal No. 2) No. 1 ignition coil connector and body earth
Check and repair harness between B-03 (terminal No. 2) No. 2 ignition coil connector and body earth
Check and repair harness between B-04 (terminal No. 2) No. 3 ignition coil connector and body earth
Check and repair harness between B-05 (terminal No. 2) No. 4 ignition coil connector and body earth

Check earthing line for open circuit and damage.

STEP 12. Check harness between ignition switch connector and ignition coil connector.

Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-02 (terminal No. 1) No. 1 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-03 (terminal No. 1) No. 2 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-04 (terminal No. 1) No. 3 ignition coil connector
Check and repair harness between C-307 (terminal No. 2) ignition switch connector and B-05 (terminal No. 1) No. 4 ignition coil connector

note

Before checking harness, check intermediate connectors C-18, C-202 and C-205, and repair if necessary.

Check power supply line for damage.

Q. Is the check result normal?

Go to Step 13 .

Repair.

STEP 13. Check harness between ignition coil connector and engine-A/T-ECU connector.

Check and repair harness between B-02 (terminal No. 3) No. 1 ignition coil connector and C-111 (terminal No. 31) engine-A/T-ECU connector.
Check and repair harness between B-03 (terminal No. 3) No. 2 ignition coil connector and C-111 (terminal No. 32) engine-A/T-ECU connector.
Check and repair harness between B-04 (terminal No. 3) No. 3 ignition coil connector and C-111 (terminal No. 35) engine-A/T-ECU connector.
Check and repair harness between B-05 (terminal No. 3) No. 4 ignition coil connector and C-111 (terminal No. 52) engine-A/T-ECU connector.

Check output line for damage.

Q. Is the check result normal?

Go to Step 10 .

Repair.