What Does B2490 Mean?
This code indicates the Body Control Module (BCM) has detected a short to battery voltage in the underhood lamp output circuit. The BCM detected voltage when the lamp should be off, meaning the circuit is receiving unintended power from the battery. This typically occurs when the positive side of the circuit has made contact with a constant 12V source, causing the lamp to remain illuminated or the circuit to draw current continuously.
Common Causes
45%
Damaged or chafed wiring harness creating a short to power between the BCM and underhood lamp
30%
Failed underhood lamp assembly with internal short to power
15%
Corroded or damaged connector pins at lamp or BCM allowing cross-circuit voltage feed
10%
Faulty Body Control Module with internal driver circuit failure
Diagnostic Steps
1
Step 1: Perform visual inspection of underhood lamp assembly, wiring harness, and all connectors for signs of damage, chafing, melting, or corrosion. Pay special attention to areas where harness contacts metal surfaces or moving components.
2
Step 2: Disconnect the underhood lamp connector and measure voltage at the lamp-side connector with ignition off and all doors closed. Should read 0V. If voltage is present, trace wiring from lamp back toward BCM for short to power.
3
Step 3: With lamp disconnected, use multimeter to measure resistance between the lamp control wire at the BCM connector (BCM side) and battery positive. Should read infinite (open circuit). If continuity exists, repair short in harness.
4
Step 4: If wiring tests pass, reconnect lamp and monitor circuit voltage with bidirectional scan tool commands. Command lamp on/off and verify proper voltage switching (0V off, 12V on). If lamp stays at 12V when commanded off, replace lamp assembly.
5
Step 5: Clear codes and perform functional test of underhood lamp operation through all normal trigger conditions (hood open, manual switch if equipped). Monitor for code return and verify proper lamp operation.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected a short to battery voltage in the underhood lamp output circuit. The BCM detected voltage when the lamp should be off, meaning the circuit is receiving unintended power from the battery. This typically occurs when the positive side of th...
The most common cause of B2490 (UNDERHOOD LAMP OUTPUT CIRCUIT Short to Battery) is: Damaged or chafed wiring harness creating a short to power between the BCM and underhood lamp
Typical repair costs for B2490 range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive as this only affects underhood convenience lighting. The lamp may remain constantly illuminated which could drain the battery if left for extended periods, but poses no immediate safety risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B2490 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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