B124B Toyota Avalon – Automatic High Beam System

Toyota-specific code — factory diagnostic data

Last updated: May 31, 2026

Definition source: Toyota factory description. Diagnostic guidance is based on factory-defined fault logic for this code.

B124B on the 2014 Toyota Avalon means: Automatic High Beam System. It is a fault code reported by the Automatic High Beam System.

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B124B Quick Answer

B124B on a 2014 Toyota Avalon indicates Automatic High Beam System. Start with a freeze-frame check and a careful inspection of the connector and wiring at the affected device before replacing any parts.

What Does B124B Mean on a Toyota Avalon?

On the 2014 Toyota Avalon, the Automatic High Beam System sets B124B when it detects a fault matching its official definition: Automatic High Beam System. This is a manufacturer-specific definition from Toyota factory diagnostic data and applies to the XX40-generation Avalon.

Symptoms

• Warning light for the affected system (check engine, ABS, airbag, or a system indicator depending on the module)
• Reduced or lost function of the automatic high beam system
• Possible related codes from other modules on the Avalon CAN/LIN network

Common Causes

• Fault in the component named in the definition (automatic high beam system)
• Open, shorted, or high-resistance wiring in the affected circuit
• Connector corrosion, water ingress, or a backed-out terminal
• Loss of supply voltage or a poor ground at the device
• Module internal fault — confirm wiring and supplies before condemning the module

Diagnostic Approach

For B124B on the 2014 Toyota Avalon you’ll want a scan tool with Toyota-enhanced coverage (Techstream-class) — generic OBD-II readers usually will not read B-codes — plus a digital multimeter and the wiring diagram.

• Confirm the code is current, not stored history, and record freeze-frame data.
• Read all modules — related codes often pinpoint the root cause faster than the headline code.
• Inspect and wiggle-test the connector at the named device while watching live data.
• Measure supply voltage and ground integrity at the device; verify the circuit against the Avalon wiring diagram.
• Substitute or isolate the suspect device only after wiring and supplies check out.
• Clear the code and road-test through one or two drive cycles to confirm the repair.

Possible Fixes

• Repair open/short/high-resistance wiring or a corroded connector
• Restore supply voltage or ground at the affected device
• Replace the failed component named in the definition
• Replace and, where required, initialise/program the module if it is internally faulty

Can I Still Drive With B124B?

It depends on the system. Automatic High Beam System faults that affect braking, the airbag/restraint system, power steering, or stability control should be repaired before further driving. Comfort or convenience faults can usually be deferred briefly, but related codes can mask one another on the Avalon network — diagnose promptly.

Source

Code definition from 2014 Toyota Avalon (XX40) factory diagnostic information (Automatic High Beam System). Symptom, cause, and diagnosis guidance summarised from standard OBD-II diagnostic practice for this platform.