Circuit Description

WARNING: This page is about a different car, the 2003 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.

A Direct Ignition System (DIS) has been adopted. DIS improves the ignition timing accuracy, reduces high-voltage loss, and enhances the overall reliability of the ignition system by eliminating the distributor. 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 the ignition timing and outputs the ignition signals (IGT) for each cylinder. Based on the IGT signals, the power transistors in the igniter cut off current to primary coil in ignition coil. Igniter also sends an ignition confirmation signal as a fail-safe measure to the ECM. DTCs set when there is no IGF signal to ECM while engine is running. See Fig 1 and Fig 2 . Possible causes are:

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

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

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