I have a conversation at the German Volvo forum and was confirmed that it could be Power unit (Ignition amplifier) failure (p/n 1367776). Does anybody know what is the unit and/or anybody faced with this unit failure?

Thanks
Oleg

It's sealed. It gets info from the ECU on which coil to fire and when. It also passes info to the ecu on which coil pack may be behaving badly. Codes are then set and the MIL turned on.

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Warren Bain - '99 V70GLT G-Valve > 80K mi, 89 300SE, '96 965 >120Kmi, near Manassas Va.. Check the 700/900 FAQ via the 'features' pull down menu. This post written with 100% recycled electrons.

The B6304 has two power stage ignition modules. They are both located on the 'ball' of the intake manifold near the bottom. One is located on the 'front' of the ball and controls cylinders 1-3 and the one at the rear controls 4-6. It's a small black plastic module and you can actually see the the one on the front of the intake manifold 'ball' from standing in front of the car on the air filter side. One bolt attaches it to the manifold.

DEWFPO
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1998 S90 068,300 and 1995 964 152,300