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The Power Stages(2) on the B6304 control the ignition, but how exactly?
The ECM takes in sensor data and grounds the - signal wire for each cylinder (coil) thru both Power Stages.
+ Power is supplied to the coils through the Green/Red wire to each coil.
The Signal wires for 3 of the cylinders goes to each P.S., where 3 wires (plus a black ground wire) come out and go to the ECM.
If the ECM is controlling timing. What is the purpose of the Power Stage? All - singal wires from the ECM go through a Power Stage before hitting the coils. They're some sort of intermediary. Nothing in the Volvo manuals describes this, and neither does my Bosch Motronic book either.
All I can think of is that it energizes the coil(s) by supplying signal/voltage for a certain duration. Just a SWAG on my part. Please enlighten me.
Your thoughts are appreciated.
DEWFPO
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1998 S90 071,245 and 1995 964 154,100
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