Electrical / earth issue with PSE circuit

[uk_monkey]

Hi Folks - a UK forum newbie here with a tech question for the collective, if I may?

 

I have an 07 C4S with the sports chassis option, sports chrono and and X51 factory upgrade. This means it only has a sport switch, which activates the PSE and softens the psm (no PASM due to the sports chassis pack).

 

The PSE is having issues though - essentially it doesn't work properly. On start up the valves are open, but as expected when the vacuum builds up they close. However they don't open when the sport button is pressed. I recently replaced the solenoid as I tested it and it had failed and for a couple of times, the new solenoid worked, but now its stopped.

 

As part of the replacement process, we tested the voltage at the solenoid plug with the sport button on and off. With it off, the plug registered and 12.5v with it on, it dropped to about 8v and the pse worked. After it stopped working, we checked the voltage at the plug again and this time it showed 14.5v when off and 10.5v with it on. So clearly the voltage isn't dropping to 0 as it should do and 10.5v is too much to switch the solenoid. Having been in communications with a couple of people on a UK forum, the feeling is that it's most likely a bad earth causing the volts not to drop to 0.

 

Has anyone on here experienced a similar issue? Could you suggest any tests that I could run in order to identify what the cause could be?

 

I'm thinking a straight forward earth to checck would be the engine loom earth near to cylinder 3?

 

Thanks in advance for your advice and assistance.

 

Monkey