Ignition Discharge Modules

Ignition
The two identical ignition discharge modules are mounted on the camshaft cover over the spark plugs. In each ignition discharge module there are 3 ignition coils whose secondary windings are connected directly to the spark plugs.
The ignition discharge modules are powered with B+ from the main relay and grounded to grounding point G7.

When the main relay is activated, B+ is supplied to the ignition discharge modules, which convert the 12V supply to 400V DC and store it in a capacitor. The 400V supply is connected to one pole of the primary windings of the 3 ignition coils.

There are 3 ignition leads running to each ignition discharge module from the control module as follows:
- Cylinder 1 (Bank 1) from control module pin 7.
- Cylinder 3 (Bank 1) from control module pin 55.
- Cylinder 5 (Bank 1) from control module pin 31.
- Cylinder 2 (Bank 2) from control module pin 54 Cylinder 4 (Bank 2) from control module pin 8.
- Cylinder 6 (Bank 2) from control module pin 32.

When the control module grounds pin 7, the other pole of the primary winding of the ignition coil for cylinder 1 is connected to the B+ input on the ignition discharge module. The 400 V supply is stepped up to a maximum of 40 kV in the ignition coil for cylinder 1.
Ignition for all cylinders is performed in the same way.

Diagnostics
- If an open circuit should occur in the power supply to the ignition discharge module, the voltage on all ignition leads will be 0 V and then trouble code P1310 (Bank 1) or P1320 (Bank 2) will be generated.
- If a break occurs in an individual trigger lead, no diagnostic trouble code will be generated.

System reaction to a fault
- Fuel shut-off to all cylinders, even if only one of the discharge modules loses its power.