Code CP_a078 was reported by the “Charge port” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The car's charge port — latch, connector lock, indicator light and proximity sensor. These codes typically appear when the connector will not lock or the car does not register that it is plugged in.
The most common type. The car logged the event and may have shown it on the screen. The range is wide — from something trivial that clears itself to something that needs attention.
This is how the fault is named inside the car's firmware. For codes without a description it is the most precise clue there is — the name itself says what the event is about.
The text below comes from Tesla's technical documentation. We leave it in the original English so that translation cannot shift its meaning.
Latch is not disengaged but is expected to be disengaged, may be frozen
info from manualCP_A078
Charge port latch does not read disengaged after being driven disengaged and cold weather mode is active
Charge port latch reads disengaged
Charge port latch may be frozen engaged, blocking cable insertion and removal
Control pilot signal remains in state B1, indicating the charge station is connected to the vehicle but is not ready to charge the vehicle, for too long while a charge cable is plugged into the charge port (CP). Charging may not start or may be interrupted unexpectedly.
info from manualCP_A066
Charge handle proximity is detected as connected to the charge port (CP) without charge handle button pressed, and control pilot signal is detected in state B1 for more than five seconds.
Charge handle proximity is no longer detected as connected to the charge port (CP) without charge handle button pressed, or control pilot signal is no longer detected in state B1. Clears after five seconds if either of these conditions is true and a charge cable is still present. Otherwise, clears immediately.
Charge port does not receive all expected CAN messages from the VCFRONT
Charge port receives all expected CAN messages from the VCFRONT
Charging may not start, charge port door and latch may not actuate, charge port LEDs may not turn on
The CP has instigated a wake up event due to pilot
Charge port detected PLC transmission failure
The CHAdeMO adapter indicates it has faulted
The CHAdeMO adapter reports it is faulted over SWCAN
The CHAdeMO adapter reports via SWCAN that it is no longer faulted, or the adapter is unplugged
Copy it exactly, letter and number included. Photographing the screen is safest — codes often differ by a single digit, and mixing them up leads somewhere else entirely.
Some codes clear after a screen restart or after the car sits locked for a few hours. If the code does not come back, it was usually a one-off glitch.
A one-off entry and a code that appears after every drive are two different things. It helps a service centre enormously if you know exactly when it shows up.
With airbags, brakes, steering and high voltage there is no point waiting it out. With the other groups you can watch and see whether the code returns at all.
Error codes are only part of the picture. For cars on TesList you also see battery health pulled straight from the vehicle, plus a price calculator that works out from current listings what a given car is actually worth today.