You need to check all of the inputs to the lambda module.The temp switch, the lambda relay, the oxygen sensor,etc. In my case it was a bad lambda relay, the module has a low failure rate. It could even be as simple as a fuse or as we saw in Richmond one car had a bad frequency valve. David Teitelbaum vin 10757 --- 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? >