B15A8: How to Diagnose & Fix — Telematics Transceiver Malfunction
3 vehicles · 2 makes
How to diagnose and fix B15A8: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Toyota Camry · 2020–2021
Toyota T-SB-0095-20 applies to some 2020-2021 Camry and Camry Hybrid vehicles that may have a depleted 12-volt battery while the ignition is off. The same DCM firmware condition may also present with B15A804 in current or history, a red SOS LED that remains on after bulb check, an inoperative Toyota App, inability to subscribe to remote services, or inability to activate Wi-Fi. Not every discharged Camry battery is caused by the DCM.
Common Symptoms
- Depleted 12-volt battery while the ignition is off
- DTC B15A804 in current or history
- Red SOS LED remains on after bulb check
- Toyota App or remote services inoperative
- Unable to activate vehicle Wi-Fi
How to Fix
Test the 12-volt battery and charging system and measure key-off draw before assigning the cause. If the vehicle is an applicable 2020-2021 Camry or Camry Hybrid and has the T-SB-0095-20 condition, follow Toyota's DCM reset and firmware-update procedure with the required battery support and Techstream steps. Continue normal parasitic-draw diagnosis when the vehicle, DCM firmware, DTC, or symptoms do not match. Do not replace the battery, a relay, or the telematics module, or buy a battery maintainer, without diagnosis.
Owner tips & cautions
- TipRecord battery state, key-off draw, DCM firmware and B15A804 history before clearing codes or disconnecting power; a weak battery and a DCM draw can coexist.
- WarningT-SB-0095-20 is limited to 2020-2021 Camry/Camry Hybrid and does not make a battery, maintainer, relay, or telematics module an automatic repair.
Sources for this issue (2)
Toyota RAV4 · 2020–2021
Toyota T-SB-0095-20 Rev2 applies to some 2020-2021 RAV4 and RAV4 Hybrid vehicles that may exhibit a depleted 12V battery while the ignition is off, sometimes with DTC B15A804, an abnormal SOS indicator or connected-services problems. Toyota's remedy is a DCM reset and firmware update once the bulletin's diagnostic checks confirm the condition. The bulletin excludes RAV4 Prime, and a depleted battery alone does not mean the battery needs replacing.
Common Symptoms
- Depleted 12V battery while the vehicle is in IG-OFF
- DTC B15A804 in current or history
- Red SOS LED remains on after bulb check
- Toyota App, remote services or Wi-Fi may be inoperative
How to Fix
Inspect the battery, terminals and connections and test the 12V battery with the appropriate diagnostic equipment. Toyota Tech Tip T-TT-0625-20 directs technicians to T-SB-0095-20 when the battery tests good and discharge remains; the bulletin then checks DCM firmware and SOS status before reset and update. If the firmware is current or the condition does not match, continue parasitic-draw and charging-system diagnosis. The original 36-month/36,000-mile basic-warranty window is generally expired, so confirm coverage.
Owner tips & cautions
- TipAsk the technician to document the battery-test result, parasitic draw and DCM firmware version before replacing the 12V battery or blaming the DCM.
- WarningRAV4 Prime is excluded from the final T-SB-0095-20 Rev2 applicability table; do not transfer this diagnosis to a Prime or to 2019/2022 vehicles.
Sources for this issue (2)
Lexus UX · 2019–2022
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B15A8 code reference
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Frequently asked questions
What does B15A8 mean?
B15A8 stands for "Telematics Transceiver Malfunction." Set by the Data Communication Module (DCM, the telematics transceiver) when its power-on self-check finds an internal error in the EEPROM (which stores the data needed to operate the Safety Connect system) or in the PLL IC (which oscillates the cellular radio frequency). It is an internal-module fault, not a wiring-continuity fault, though a poor connection at the DCM connector can also set it. Toyota has documented that this DTC can be stored during manufacturing and shipping without indicating any real vehicle defect.
What are the most common causes of B15A8?
The most common causes of B15A8 are: Internal EEPROM or PLL IC failure inside the DCM / telematics transceiver, Poor electrical connection or corrosion at the DCM connector, DCM firmware fault (including the DCM firmware that keeps the module awake and drains the 12V battery), Code stored during vehicle manufacture or shipping with no actual fault present. The specific cause varies by vehicle.
How much does it cost to fix B15A8?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by B15A8?
Au7o has documented B15A8 across 3 vehicle models from 2 manufacturers: Lexus, Toyota.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.