Code PCS_a108 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.
PCS detects it is misconfigured, please refer to the alert toolbox article to decode the miss configuration condition and fix them accordingly
PCS detects there are misconfigurations.
The misconfiguration condition(s) is fixed.
DCDC and/or AC charging may not function properly
All charger phases are faulted, not able to deliver power to the battery pack
All charger phases are faulted and retries are exhausted
Charger is not able to regulate its intermediate bus voltage
Charger intermediate bus voltage regulator error exceeds threshold
Charger intermediate bus voltage regulator error is below clear threshold
PCS does not receive CAN messages from HVP
Charger does not receive all expected CAN messages from high voltage processor
Charger recieves all expected CAN messages from high voltage processor
PCS DCDC detects resonant tank over current event
DCDC converter detects resonant tank current exceeds overcurrent threshold
PCS CAN receiver encounters error while receiveing message
Power conversion system CAN receiver encounters error while receiveing message
Power conversion system CAN receiver does not detect any errors for more than five seconds
Inability to AC charge, inability to precharge HV bus, inability to support 12V system, inability to drive
PCS detects one of its logical power rail's measurement becomes irrational
Power conversion system detects that a logical power rail voltage is outside expected range for more than one second
Power conversion system detects that all logical power rail voltages are within expected range for more than one second
Inability to precharge HV bus, inability to support 12V system, inability to AC charge, inability to drive
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.