| the primary coil in the coil pack must be grounded. There are two individual coil windings in the coil. One is the primary and one is the secondary. When the primary coil is powered on it induces a current in the secondary coil. The secondary coil is connected between the spark plug and ground. The primary is connected between battery voltage and the PTU. The ECU drives the PTU with a very low voltage, somewhere in the order of .6 volts IIRC. The ignition voltage to the PTU from the ECU is one of the only positive voltages that comes from the ECU. Most everything else from the ECU is a ground signal. Before I go into the possible causes I'll explain how the PTU works so you'll understand the possible cause of the problem a little better. The PTU is a block of electronic switches made out of a patchwork of transistors. The transistors are electronic switches. There are two common types of transistors. NPN and PNP. NPN transistors use a positive signal at their base to cause them to conduct. These are what are in the PTUs. They are fed a positive signal from the ECU which allow them to turn on. When they turn on they provide a path to ground for the coil pack primary coil. These are the things that are going to cause the coil to get hot in the state you describe. 1. The PTU transistor for coil 1 is shorted. This could cause a constant ground to the primary coil which is always hot with battery voltage during normal operation. 2. The transistor in the ECU for coil 1 is shorted. This can cause voltage to always go to the PTU. The ECU uses SMD transistors to drive the PTU. I've repaired ECUs that have had all of these transistors shorted. 3. You have a shorted wire on the ground side of the primary coil of the coil pack. Turn the car ignition off and remove the key. Disconnect the PTU on the side that goes to the coil packs. Check all three wires to the coil pack. Only one should have continuity to ground. If two wires have continuity to ground then you have a short. 4. If there was no short found then reconnect the PTU and perform the same check again. If you now find two wires that are grounded then you have a bad PTU. If not then you may have a bad ECU.
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21:43:26 02/20/15
