Code APS_w040 was reported by the “Autopilot — secondary processor” controller in the car. The letter “w” in the middle places it among entries of the warning type.
Had code APS_w040 as well? Tell others how it turned out for you →
The second, supervising processor inside the Autopilot computer. It checks the primary processor's work and guards safety functions, chiefly automatic emergency braking. Codes from here often accompany APP codes and clear once camera calibration finishes.
The car is flagging that something is not right. Driving is usually still possible, but some function may be limited.
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.
One of the AP power rails is not at the desired voltage level
APS detects that voltage level of a power rail is beyond of nominal range
Clears when the voltage level reaches the expected value
Some parts of the AP board may not be powered up fully
Radar sensor health goes back to nominal
APS does not receive one or more msgs from ESP for more than 10 cycles
Clears when ESP msgs are received again
Features that depend on ESP msgs will be disabled
APS detects that CAN msg counter, length, checksum etc are not as expected
Clears there is no error in CAN msg reception
May cause certain msgs to timeout
LWIP stack recovers from errors
APS doesnt receive PARK msgs for more than 10 cycles
APS starts receiving msgs from PARK
APS computer executed a bad instruction
APS computer generates an exception when bad instruction is executed
Clears after reset / power cycle
AP features will be temporarily disabled
APS CAN driver has buffer full or other transmit errors
Clears when CAN msg can be transmitted successfully
Other ECUs may complain that AP msgs are not present
Warns if APS detects communication issues with the GPS receiver
APS detects a fault in GPS communication
GPS receiver communication is re-established
Navigation and Autosteer will be temporarily broken
This part is written by you. If you have had code APS_w040, tell us when it appeared, what brought it on and how it ended — for the next person, one such sentence is often worth more than the entire service documentation.
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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.