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P257A Severity
Once the vehicle's onboard system no longer detects the issue, most codes will disappear on their own. If your vehicle still has this code, however, it should be properly diagnosed to avoid a more serious problem.
For a proper diagnosis, RepairPal Certified shops have the equipment, tools, and expertise.
Moderate severity codes might not threaten the vehicle's safety or functionality immediately, but you should still get it diagnosed within a reasonable time frame to keep your car running well.
Diesel vehicles have a separate vacuum pump an reservoir because they cannot utilize vacuum from the engine the way a gasoline vehicles can. The engine control module (PCM) tells the vacuum pump when to turn on an off. If the PCM cannot control the pump, it will set code P257A.
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OBD-II Code Climate control systems will not work is defined as a Vacuum Reservoir Control Circuit/Open
Diesel vehicles have a separate vacuum pump an reservoir because they cannot utilize vacuum from the engine the way a gasoline vehicles can. The engine control module (PCM) tells the vacuum pump when to turn on an off. If the PCM cannot control the pump, it will set code P257A.