Front Trunk (Frunk) Open
The TESLA-UI_A004 (Tesla) EV fault code means: Front Trunk (Frunk) Open. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- Soft reset and software fix: $0 DIY. 12V battery replacement: $80-$150 DIY or $150-$250 at a shop. eMMC chip reball/replacement by an independent EV specialist: $300-$600. Full MCU2 replacement at an independent shop: $500-$900. Tesla service center MCU3 upgrade (if eligible): $1,200-$1,500 with labor.
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Common Symptoms
- Alert UI_A004 shown on the touchscreen
- The vehicle may log the alert without any change the driver notices
Probable Causes (Ranked by Likelihood)
- The vehicle reported UI_A004. Tesla's firmware identifies this alert as "UI_a004_FrunkOpen" — the front trunk being open or not latched — a notification, not a fault. High
Frequently Asked Questions
What does UI_A004 mean?
Front Trunk (Frunk) Open. Tesla's firmware identifies it as "UI_a004_FrunkOpen".
Can a generic OBD2 scanner read this?
No. Tesla alerts are a manufacturer-specific system and appear in no SAE standard, so a generic OBD-II scan tool cannot read or clear them. The alert text on the touchscreen and the Tesla app are the authoritative sources.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Read the alert text on the touchscreen exactly as shown — Tesla's own wording is more specific than any third-party list, this page included.
Check for a Tesla service bulletin or a pending software update; a number of alerts clear on their own after an over-the-air update.
If the alert persists, request service through the Tesla app. Tesla alerts are not standard OBD-II codes and a generic scan tool will not read or clear them.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- Tesla alert dictionary (canonical firmware alert identifiers)community-maintained dictionary, not an official manufacturer document
Commonly Affected Vehicles
- Tesla Model 3 (RWD, Long Range AWD, Performance) -- 2017-2021 builds with MCU2
- Tesla Model Y (LR AWD, Performance) -- early production units with MCU2
- Tesla Model S (LR, Plaid) -- pre-2022 refreshed units on MCU2
- Tesla Model X (LR, Plaid) -- pre-2022 units with MCU2 and tri-screen layout
- Tesla Model 3 (RWD, Long Range AWD, Performance) -- any build after a partial OTA failure
- Tesla Model Y (LR AWD, Performance) -- units with a degraded 12V lithium accessory battery
- Tesla Cybertruck (RWD, AWD, Cyberbeast) -- MCU3 platform, less common but reported after OTA interruptions
Related Codes
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