Originally Posted by ah-kay

You may have 2 problems. A vacuum leak and a switch problem at the door. The 190D works on 1 vacuum line. The pump sucks vacuum ( negative pressure ) to lock and positive pressure to unlock.

You need a hand held vacuum pump, like a Mityvac to diagnose the leak. The vacuum lines are underneath the carpet. Try to look for T connections, remove the T and identify where is the pump side and where is the lock side. Hook up the Mityvac to the lock side and pump away. The door lock or locks should lock. If not then that line has a leak or the pod(s) downstream is faulty. Then work on other sections.

The switch is at the driver door. It could be the switch or the vacuum pump works intermittently. Change out the pump and if it still happens then it could be the door lock switch.

Good luck.