Code CC_a039 was reported by the “Wall Connector” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The controller inside the Tesla Wall Connector. These codes describe the state of the home installation — connector temperature, pilot signal, earthing, supply voltage. The fault therefore sits in the charger or the wiring, not in the car.
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.
Wall connector real-time processor is too hot
Real-time processor exceeds 85C
Real-time processor cools to below 65C
Charging will be interrupted and one red blink on LEDs
info from manualCC_A017
Contactor detected as closed when it should be open
info from manualCC_A010
Wall connector detects voltage on the contactor output when it should be open
User resets by cycling cable, reset button, or power cycle
Wall connector will not operate and there is a potential hazardous voltage present on the charge handle
info from manualCC_A016
Wall connector internal voltage reference is out of acceptable range
Internal voltage reference leaves acceptable range
Internal voltage reference enters acceptable range
AC RMS input voltage is too high
info from manualCC_A007
AC RMS input voltage exceeds 320 V RMS for NA or 290 V RMS for EU/CN for more than 2 seconds
AC RMS input voltage falls below 310 V RMS for NA or 280 V RMS for EU/CN for more than 2 seconds
Wall connector will not allow charging while the input voltage is too high
PCBA temperature exceeds threshold
PCBA temperature falls below threshold
Charging rate will be reduced by 50%
Wall connector is configured as a slave but no master was detected
info from manualCC_A021
Wall connector is configured as a slave but no master is present on the sharing network
Wall connector is reconfigured or a master becomes present on the sharing network
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.