If you spend anytime more involved with vehicles than reading a Haynes manual at some point you will have to work out what someone means by KL31
KL is the abbreviation for ‘klemme’ which is the German term for connector/connection, or ‘Klemmenbezeichnungen’ which means Terminal designations. This is mostly encoded in DIN 72552
- KL15 is ignition switch position #2 (on)
- KL30 is battery positive, there will be ’12 VDC’ on this at all times
- KL31 is battery negative, (unswitched)
- KL50 is ignition position #3 (start)
- KLR means ignition switch position #1 (Accessory) In this mode the radio/IVI, windows, etc will be powered on, but the traction motor will not be enabled (ICE or EV), there may be limited HVAC (Heating Ventilation and Air Conditioning) due to the HVAC compressor, and the heater not being powered.
Normally when talking about KL30 and KL31, it is the positive and negative poles of the vehicle battery.
Historically the three modes of the ignition gear correspond to the opening and closing of three relays on a vehicle, however, in all modern vehicles there will be more states, and chances are fewer relays as semiconductor switching components have taken over.
Featured image Lunawisp, CC BY-SA 3.0