The car in the Real Fix below sounds like it has a mind of its own. Manufacturers including Mercedes-Benz use a pneumatic, or vacuum controlled system, for activating certain components instead of using DC voltage. The system has unique failures due to its design. Over time, the hoses and lines used to transport the vacuum can deteriorate and cause a plethora of issues.
In the Real Fix below, water saturated the pneumatic pump and caused some pretty spooky results.
1999, Mercedes-Benz SLK230, 2.3
Accessories and Body, Cab
B1021, B1024, B1025, Replaced Pneumatic System Equipment Pump
The customer states the vehicle’s alarm is sounding on its own and the door locks will lock and unlock intermittently.
Connected a scan tool and found codes: B1021 – CAN Data Lines Not Communicating with PSE; B1024 – CAN Data Lines Low and B1025 – CAN Data Lines High. Gained access to the pneumatic system equipment pump, inspected the pump and found the foam housing was saturated with water. Checked the wiring harness and connector terminals to the pneumatic system equipment pump for additional signs of water intrusion, but found no further signs of water saturation. Determined the water damage to the pneumatic system equipment pump was the source of the trouble codes and was found to be the root cause of the vehicle’s abnormal activity.
Replaced the pneumatic system equipment pump, cleared codes, performed a road test and verified the vehicle operated properly. The customer’s concerns did not return.
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