Circuit Description

WARNING: This page is about a different car, the 2003 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.

A Direct Ignition System (DIS) has been adopted. The DIS improves the ignition timing accuracy, reduces high-voltage loss, and enhances the overall reliability of the ignition system by eliminating the distributor. The DIS is a one-cylinder ignition system which ignites one cylinder with one ignition coil. In the one-cylinder ignition system, the one spark plug is connected to the end of the secondary winding. High voltage generated in the secondary winding is applied directly to the spark plug. The spark of the spark plug passes from the center electrode to the ground electrode.

ECM determines ignition timing and outputs the ignition signals (IGT) for each cylinder. Based on IGT signals, the power transistors in the igniter cuts off the current to the primary coil, and spark is supplied to the spark plug that is connected to the end of the secondary coil. At the same time, the igniter also sends an ignition confirmation signal (IGF) as a fail-safe measure to the ECM. DTC is detected if there is no IGF signal to ECM while engine is running. See Fig 1 and Fig 2 . Possible causes are:

Open or short in IGF1 or IGF2 and IGT1-IGT8 circuit from ignition coil with igniter to ECM.
Faulty No. 1-8 ignition coil with igniter.
Faulty ignition system.
Faulty ECM.

Fig 1: Identifying Igniter Coil Circuit (1 Of 2)

Fig 2: Identifying Igniter Coil Circuit (2 Of 2)