Code PCS_a009 was reported by the “Power conversion system (PCS)” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The Power Conversion System — the combined onboard charger and DC/DC converter. It handles charging from the socket and generating the 12 V supply. These codes mostly show up as slower or interrupted charging.
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.
Charger is not able to regulate its input current
Charger PFC current regulator error exceeds threshold
Charger PFC current regulator error is below clear threshold
PCS DCDC has reached its max hardware power capability
Charging is inhibited due to low 12V
Charger detects 12V bus voltage is below 7V for more than 500ms
Charger detects 12V bus voltage is above 7V
PCS has detected at least one damaged AC charging phase, AC charging power will be limited
Power conversion system detected reset while enabling a phase, and did not attempt to re-enable phase
Power conversion system is reset or power cycled
Charger detects wall power is removed while charging
info from manualPCS_A017
Charger detects wall power was unexpectedly removed while charging
Charging faulted due to too large of a voltage drop between starting charge and during charge
info from manualPCS_A054
Charger detects greater than 14% input voltage drop after ramping power
Inability to AC charge, possibly due to bad wiring external to vehicle
PCS is not able to boot CPU2 and AC charging functionality is lost
Power conversion system was unable to boot CPU2
Power conversion system boots CPU2 successfully
DCDC PWM enable hardline de-asserted while DCDC was commanded to be active
DCDC converter detected that enable line was de-asserted unexpectedly
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.