If you need to replace the plug for the frequency valve, then you can cut off the plug from a Volvo from a junkyard and use it. If I remember correctly the frequency valve is only supposed to buzz when the engine is running. I'm at work right now, so I don't have my manuals with me. But check the power supply to the LAMBDA module (I think there's 2). I could be that somewhere down the line power is either not making it to the module itself, or perhaps the LAMBDA relay, or even something else. I don't get home untill late this evening, but I'll take a look at the wiring diagram to see if I can find out some points for you to check. Off hand the only thing I can think of would be to remove the LAMBDA relay (top row, 2nd from the right) and check that all contacts are clean, and that the female contacts in the socket are at the top are making contact. Also check the RPM relay as well and do the same for it. -Robert vin 6585 --- In dmcnews@xxxxxxxxxxx, "Walter" <Whalt@xxxx> wrote: > Robert, thank you very much for your help! :) > > To Robert & everyone else: > > Is the frequency valve supposed to buzz when the ignition is switched on? > Or does it only buzz while the engine is running? >