OBD2 Code B2490: Underhood Lamp Short to Battery
The B2490 diagnostic trouble code indicates that the body control module (BCM), front electronic module (FEM), or the relevant lighting module has detected a short circuit to battery positive (B+) in the output circuit for the underhood lamp. The module monitors the expected load and sets this code when it sees a permanently high voltage level, equivalent to direct contact with battery positive, preventing normal on/off control of the hood light. This fault is confined to the comfort and body subsystem and does not affect the drivetrain, brakes, steering, or active safety systems. The code typically sets during routine diagnostic tests performed by the module after ignition cycles.
1. Commonly Affected Makes
2. Most Common Causes
- Underhood lamp harness wiring shorted to battery positive (B+)
- Damaged underhood lamp with shorted filament or internal resistance
- Harness or lamp connectors with deformed, corroded, or moisture-bridged pins
- Failed internal output driver in the control module (BCM, FEM, or lighting module)
- Aftermarket electrical accessories or alarms altering the original lamp circuit integrity
3. Symptoms You Will Notice
- Underhood lamp stays on continuously or fails to turn off
- Underhood lamp does not illuminate when hood is opened
- Check Engine Light or service lamp warning may illuminate
4. Step-by-Step Diagnosis
Verify the underhood lamp operation and check for constant illumination
Inspect the underhood lamp harness for physical damage, chafing, or shorts to B+
Check the lamp connector for bent, corroded, or wet pins
Test the lamp bulb for internal short using a multimeter
Disconnect aftermarket accessories tied to the underhood lamp circuit
If wiring and lamp check out, suspect a failed module output driver and test with a scan tool
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is safe to drive. This code affects only the underhood lamp circuit and does not impact critical systems like brakes, steering, or engine performance.
How much does it cost to fix?▼
Repair costs typically range from $50 to $200 for a simple bulb or connector fix, up to $400-$800 if the control module needs replacement.