Code EPAS3P_a125 was reported by the “Power steering — 3rd gen, primary” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The primary channel of third-generation power steering. Newer cars have a redundant steering system — this is its main half.
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.
Torque sensor zero point calibration out of range
Motor Angle trim service not performed or incorrect value stored
Torque sensor zero point callibrated
Reduced steering assist, EAC inhibited, SASQF = UNDEFINABLE_ACCURACY
Invalid ESP_wheelRotationChecksum value received
Unexpected ESP_wheelRotationChecksum value received
EPAS observes expected ESP_wheelRotationChecksum value
Damping controller correlation error
Invalid DI_torque1Counter value received
DI_torque1Counter is not incrementing correctly
EPAS observes DI_torque1Counter incrementing correctly
External Angle Controller is inhibited
Active return controller correlation error
Proportional-integrator motor control error counter exceeds 25% of threshold
External angle controller correlation error
|torque command path1 - path2| > 0.1Nm
High-side phase W undervoltage
Regulator internal error observed
Motor position sensor 2 magnetic field not detected
Difference between torque sensor 1 and 2 exceeds threshold
Calibrate torque sensors 1 and 2
Difference between battery and bridge voltage exceeds threshold
Gate drive supply undervoltage
Motor position sensor not calibrated
Calibrate motor position sensor
Assist redcued due to supply overvoltage
Assist reduced due to supply overvoltage
Proportional-integrator motor control error counter exceeds 85% of threshold
Invalid APS_eacMonitorChecksum value received
Unexpected APS_eacMonitorChecksum value received by EPAS
Expected APS_eacMonitorChecksum value received by EPAS
Invalid motor rotation direction
Powerpack Polarity service not performed or incorrect value stored
Current sensor correlation error
|high freq current - low freq current| > 3.34 A at motor speed < 500 rpm
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.