Unplugging BCS

[ddmgti]

Was thinking of trying this as a bit of an experiment, background is, i,ve low boost pressure ie 6 psi in 2nd Gear, car is throwing a Code 4-3-3, Rear Knock sensor Signal, which i believe may be holding Boost back. I have no CEL Light on, it does not come on at start up, either removed by previous owner or Bulb blown, my thinking is if BCS is unplugged ECU does not have control over Boost pressure therefore no signal to BCS To back off boost or will BCS just go in to safe mode ie, no boost, I have not checked Sensors or wiring yet due to bad weather, just wondering if this will point me in right direction ie, Knock sensor, tried adjusting Wastegate at weekend but locking nut had siezed it also has decreased diameter due to rust etc, small hole in Metal Pipe over engine plugged with Self-tapper, any advice on this please,Ta.

[p fandango]

Was thinking of trying this as a bit of an experiment, background is, i,ve low boost pressure ie 6 psi in 2nd Gear, car is throwing a Code 4-3-3, Rear Knock sensor Signal, which i believe may be holding Boost back. I have no CEL Light on, it does not come on at start up, either removed by previous owner or Bulb blown,

put a new bulb in & replace the knock sensor. With that fault showing the ECU will be lowering the boost

my thinking is if BCS is unplugged ECU does not have control over Boost pressure therefore no signal to BCS To back off boost or will BCS just go in to safe mode ie, no boost, I have not checked Sensors or wiring yet due to bad weather, just wondering if this will point me in right direction ie, Knock sensor,

i'm afraid it works the other way around, the actuator is set lower & the BCS helps to raise the boost. Unplugging the BCS will probably lower to the boost even more than it currently is. Even in limp home i think the ECU gives the BCS a small duty cycle & raises the boost over actuator pressure

tried adjusting Wastegate at weekend but locking nut had siezed it also has decreased diameter due to rust etc, small hole in Metal Pipe over engine plugged with Self-tapper, any advice on this please,Ta.

personally, don't mess with the actuator get the faults fixed then see how its running

according to a diagram i've found, it looks like the 2 knock sensors are either end of the inlet manifold. Volvo do what they call a knock sensor service kit (the loom pictured in the top left of the pic) which is part number 272234

[ddmgti]

Thanks mate,pretty much what i,m thinking, will check sensor wiring/connectors first, if it ever stops raining.

[ddmgti]

Just had a look on Fleabay, seems to be different types, different to your diagram, some with two connectors, some with one, i have 2 connectors down next to radiator its a 1995 model, all i can see at the moment, would you reckon two seperate connectors rather than one, as shown on the diagram? and are they connected at actual sensor or hardwired if you know what i mean, ie 2 connectors on wiring, Ta.

[p fandango]

Just had a look on Fleabay, seems to be different types, different to your diagram, some with two connectors, some with one, i have 2 connectors down next to radiator its a 1995 model, all i can see at the moment, would you reckon two seperate connectors rather than one, as shown on the diagram? and are they connected at actual sensor or hardwired if you know what i mean, ie 2 connectors on wiring, Ta.

looking at the original diagram it looks like they may have upgraded to the single plug, & the service kit includes a 2 plug to 1 plug adaptor. I've no idea if they are hard wired or not, in another diagram it did show just the sensor with no wiring but didn't give a part number for it, whether that means you can use your existing wiring but they won't sell it seperate i do not know mate