Many cars now use Direct Ignition systems with ignition coils integrated into an assembly that connects directly to the spark plugs. Diagnosing problems with Direct Ignition systems can be challenging, but once a faulty Direct
Ignition system is diagnosed, it can be replaced very easily.
The most common trouble codes that you will find in OBD II cars are codes 301/302/304/351/358 which indicate a misfire in a single cylinder. These misfires can be caused by many factors including fouled plugs, damaged coils, corroded wire terminals to the DI, contaminated fuel, compression loss, low fuel pressure or burnt valves. Keep in mind that code P0300 (lean/rich mixture code) is likely due to a fuel or vacuum leak issue. Cranks sensor codes are usually code 320/340 or in that range.
|BE CAREFUL! EXTREMELY HIGH VOLTAGE!|
Turn the Cassette over & put the plugs in the holes, ground each plug to the negative battery terminal and turn the engine over watching the spark. If there is a problem with the cassette, one of the plugs will have no spark or a very weak spark. Also, when you turn the ignition key off there should be a shower of sparks that runs the length of the plugs several times. There have been occasions when the DI cassettes would test ok when turned upside down but would fail when turned back over to install into the valve cover! Oil leakage from the individual coils of the cassettes have also been a problem. Oil leaks can be identified by noting that there is oil in the spark plug hole!
It is best to make sure the car has not been operated for several hours. This allows the engine to cool down, and also allows any high voltage possibly stored in the direct ignition subsystem to be discharged. To replace the direct ignition system disconnect the cable that connects it to the engine control subsystem. This cable is keyed, so that it is
only possible to re-connect when the pins are aligned properly. There is also a locking mechanism on the connector, that snaps into place to assure the connector does not come loose. For cable removal it is necessary to
unlock this connector. Gently pry the purple tab out as shown below.