[SOLVED] BYD Fuse Box Diagram (Cabin & Under-Bonnet) + How to Pull the Telematics Fuse to Fix "No 4G Network / App Offline"

BennyMorrison

If your BYD shows "No Network" / empty 4G signal bars on the top right of the DiLink screen and the BYD Mobile App stops updating your vehicle status (even after holding down the centre console volume roller for 10 seconds to reboot the screen), it means the T-Box (4G Telematics Cellular Modem) is hung on a stale mobile tower handshake.

Rebooting the screen only restarts the Android head unit — it does not cut 12V power to the T-Box modem! Here is the 2-minute fix without disconnecting the 12V battery:

Method 1: Easiest Under-Bonnet 12V Negative Terminal Reset (10mm Spanner)

Pop the bonnet (pull the driver's footwell lever twice).
On Atto 3 / Dolphin / Sealion 6, loosen the 10mm nut on the Negative (-) 12V battery terminal, lift the cable off for 90 seconds, and reconnect.
This hard-resets the T-Box modem and re-registers the eSIM on Telstra/Optus (AU), EE/Vodafone (UK), or Spark (NZ) within 30 seconds!

Method 2: Cabin Fuse Box T-Box Fuse Pull & Dashcam Hardwire Tap Guide

Located behind the removable panel below the steering column (right-hand side on RHD AU/UK/NZ cars):

T-Box / Telematics Module Fuse: 7.5A or 10A Micro2 fuse (labelled T-BOX / ICALL on the back of the fuse cover lid). Pull for 60 seconds and re-insert.
Best Switched ACC Fuse for Accessories: 15A Cigarette Lighter / Auxiliary Power fuse.
Best Constant 12V (B+) Fuse: Spare 10A slot in column B (always use a Micro2 Add-A-Circuit fuse tap with the cable pointing towards the load side!).

ThamesValleyEV

Lifesaver!! My Atto 3 in Sydney lost 4G connection for 4 days after parking in a B4 underground car park in the CBD. Rebooting the screen 5 times did nothing. Pulled the T-Box fuse under the steering column for 1 minute as you described, popped it back in, and full 4G bars + BYD App remote AC control came back instantly!

Sophie_Taylor

For BYD Seal owners where the 12V lithium battery is tucked under the rear seat cushion: pulling the T-Box fuse in the driver's knee bolster fuse box (using the white plastic fuse puller clipped inside the under-bonnet PDC box) is 10x easier than lifting the rear seat.

Megan_ACT_EV

Quick tip: keep a 10mm ratcheting spanner in the glovebox alongside the plastic fuse puller. Takes up zero space and fixes 99% of modern EV computer glitches in 2 minutes.

Rob_EVChargerInstaller

Thanks for confirming the Micro2 blade fuse size! Ordered a pair of Micro2 Add-A-Circuit taps from Jaycar to wire in my UHF radio display and radar detector in Auckland.

ElenaRostova

Note that since the mid-2026 T-Box firmware update, BYD added an automatic 24-hour modem watchdog timer that self-reboots the eSIM if data ping fails, so 4G dropouts after underground parking are way rarer now!

Daniel_UK_EV

Good catch on those specifications. I checked the service manual torque specs and fuse layout over the weekend and everything matches what you outlined here.