B2499: Courtesy Lamp Circuit Malfunction
The B2499 code indicates that the body ECU (Main Body ECU / Integration Relay) has detected a fault in the courtesy lamp output circuit (dome/map light). This occurs when the voltage on the lamp control circuit does not match the commanded state (e.g., open circuit, short to ground, or short to battery) for a calibrated period.
1. Commonly Affected Makes
2. Most Common Causes
- Blown or incorrect type courtesy lamp bulb
- Short to ground in the courtesy lamp circuit wiring
- Open circuit in the wiring between the body ECU and the courtesy lamp
- Internal output driver failure in the body ECU (Main Body ECU)
- Loose, corroded, or damaged connector at the lamp or ECU
3. Symptoms You Will Notice
- Courtesy lamp (dome/map light) does not operate or operates intermittently
- Lamp stays on continuously or fails to turn off
- Check engine light or warning lamp may illuminate
4. Step-by-Step Diagnosis
Verify the courtesy lamp bulb condition and correct type
Inspect wiring and connectors for damage, corrosion, or loose connections
Check for short to ground or open circuit in the lamp circuit using a multimeter
Test the body ECU output by commanding the lamp on/off with a scan tool
If all else is normal, suspect a faulty body ECU
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive. The fault only affects interior lighting and does not impact vehicle drivability or safety systems.
How much does it cost to fix?▼
Repair costs typically range from $50 to $200, depending on the cause. A bulb replacement is cheap, while ECU replacement can be more expensive.