Code No. P0300 Ignition Coil (Power Transistor) System

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).

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.

Check Conditions

Judgment Criteria

The determination signal for the open circuit is continuously output from the confirmation signal circuit for the ignition built in the engine-A/T-ECU.

DIAGNOSIS PROCEDURE

Go to Step 2 .

Repair or replace.

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

	Go to Step 3 .

	Replace ignition coil.

OK: 2Ω or less

Go to Step 4 .

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.

Go to Step 5 .

Repair or replace.

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.

Go to Step 6 .

Repair.

	Replace engine-A/T-ECU.

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