Code DI_a126 was reported by the “Drive inverter” controller in the car. The letter “a” in the middle places it among entries of the alert type.
The Drive Inverter — the power electronics that drive the motor. Codes from here show up as reduced power, a message about limited acceleration or, in worse cases, an inability to drive. Temperature codes are common too: the inverter protects itself under sustained load.
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.
Drive Inverter Warning: No functional heatsink temperature sensors
Drive Inverter Warning: Phase current imbalance
Imbalanced phase currents detected. See payload signals for reason of trigger
Reason of trigger is no longer present
Drive Inverter Temp Estimator Implausible
Drive Inverter Warning: Unit limp mode triggered
Abnormal condition detected within drive unit subsystem. Look at limpReason in alert for exact trigger.
Drive Inverter Warning: Motor encoder error detected in hardware
Drive Inverter Warning: Oil pump failure
Loss of communication or power to oil pump, or persistent oil pump motor stall or fault occurred
Clears at the start of a drive cycle, if set condition is not present anymore
Initiates reduced drive unit performance and a speed limit on the vehicle, due to reduced gear lubrication and motor cooling
Drive Inverter Warning: Motor over speed
Drive Inverter Warning: Power stage current observer complete
Drive Inverter Warning: LIN communication error
Drive Inverter Warning: Battery under voltage
HV bus voltage (refer to busVoltage) drops below lower voltage threshold (refer to busHighLimit)
HV bus voltage rises back above lower voltage threshold
Drive Inverter Warning: Active damping error
Drive Inverter Warning: Ambient over temperature
Ambient temperature (refer to pcbTemp) exceeds upper temperature threshold
Ambient temperature drops below upper temperature threshold
Drive Inverter Warning: Rotor flux and offset learning routine is in progress
Drive Inverter Warning: Phase B peak over current detected in software
Drive Inverter Warning: Power Stage Not Ready
Triggers ODIN service to upload log buffer
Drive Inverter Warning: Heatsink under temperature
Heatsink temperature (refer to heatsinkTemp) drops below lower temperature threshold
Heatsink temperature rises above lower temperature threshold
Drive Inverter Warning: Ambient sensor bad
Abnormal temperature measurements from ambient sensor
Ambient sensor returns to rational temperature measurements
Unable to monitor ambient sensor temperature
Drive Inverter Warning: Phase C peak over current detected in hardware
Diagnsotic Alert: Irrational rotor offset detected
Rotor offset mean estimator is above minimum rationality threshold at very low absolute torque outputs
Rotor offset mean estimator falls below minimum rationality threshold
Diagnostic alert data only, may indicate reduction in torque or excess heat accuracy
Drive Inverter Warning: DC bus disconnected
Drive Inverter Warning: Active discharge is on but bus voltage remains high
Bus voltage is high while active discharge is ON
Bus voltage is low or active discharge is off
Potentially exposed high voltage
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.