Code EPAS3P_a064 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.
Phase compensation correlation error
Motor position sensor 1 magnetic field not detected
Mismatch between primary and secondary ECU application cyclic redundancy check
Primary and Secondary ECU are running different versions
Flash primary and secondary ECU with same version
Phase U bootstrap undervoltage
Torque sensor 2 observed failure with the linearity calibrations
Invalid ESP_wheelSpeedsChecksum value received
Unexpected ESP_wheelSpeedsChecksum value observed
EPAS observes expected ESP_wheelSpeedsChecksum
High-side FET startup check error
Invalid RCM_intertial1Counter value received
Invalid SCCM_steeringAngleSensorStatus value received
Invalid SCCM_steeringAngleSensorStatus value received by EPAS
Valid SCCM_steeringAngleSensorStatus value received by EPAS
Gate drive voltage regulator undervoltage
Phase W bootstrap undervoltage
Yaw damping controller correlation error
|torque command path1 - path2| > 10A (0.6Nm)
Invalid VCFRONT_LVPowerStateChecksum value received
Unexpected VCFRONT_LVPowerStateChecksum received
EPAS receives expected VCFRONT_LVPowerStateChecksum value
Proportional-integrator motor control error counter exceeds 50% of threshold
Motor position sensor 2 logic error
The electric power assist steering (EPAS) Electronic Control Unit (ECU) is not receiving the wheel rotation message, resulting in a reduced amount of steering assist to preserve vehicle stability.
The electric power assist steering (EPAS) Electronic Control Unit (ECU) does not receive the wheel rotation message.
The electric power assist steering (EPAS) Electronic Control Unit (ECU) receives the wheel rotation message.
The power steering is operational but the level of assist is decreased and External Angle Controller is inhibited.
Torque sensor 2 signal not received
Torque Sensor 2 signal not received by EPAS
Invalid RCM_intertial1Checksum value received
Invalid UI_chassisControlChecksum value received
Unexpected UI_chassisControlChecksum value received
EPAS recevies expected UI_chassisControlChecksum value
UI_chassisControl message not received
High-side phase U undervoltage
SCCM_steeringAngleSensor message not received
SCCM_steeringAngleSensor message is not received by EPAS
SCCM_steeringAngleSensor message is received
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.