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Home / DTC / B2490 — UNDERHOOD LAMP OUTPUT CIRCUIT Short to Battery

B2490 — UNDERHOOD LAMP OUTPUT CIRCUIT Short to Battery

Detailed page for trouble code B2490.

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Code

B2490

Other B — Body

UNDERHOOD LAMP OUTPUT CIRCUIT Short to Battery

Brand: Other
Type: B — Body
Views: UK: 20 EN: 16 RU: 18
AI status
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Page language: EN

Causes

  • Damaged or chafed wiring contacting a constant battery feed
  • Faulty or shorted underhood lamp (bulb/LED) or lamp assembly
  • Corroded/loose connector or pin causing power feed to bleed into the output
  • Failed body/control module output driver (internal transistor)
  • Aftermarket accessory tied into the lighting circuit incorrectly
  • Blown or incorrect fuse or fusible link allowing backfeed

Symptoms

  • Underhood lamp stays ON continuously or comes on unexpectedly
  • Battery draining when vehicle is off (parasitic draw)
  • Blown fuse or repeated fuse failures on lighting circuit
  • Related body module warnings or stored body DTCs
  • Lamp does not respond to hood switch or lighting control

What to check

  • Scan for stored body/module DTCs and freeze-frame data; confirm B2490 is current or historic
  • Visual inspection of underhood lamp, connector and harness for chafing, pin damage, corrosion or aftermarket splices
  • With ignition off, measure voltage at the underhood lamp connector pins (expect ~0V or open when off; seeing battery ~12V indicates short to battery)
  • Disconnect the lamp connector and re-check the output voltage at the module/harness side to determine if short is in lamp/connector or upstream in harness/module
  • Check related fuses and fusible links for correct rating and evidence of overheating
  • Perform a parasitic draw test if battery drain is suspected

Signal parameters

  • Expected OFF voltage at lamp output: approximately 0 V (open) / low impedance to module ground control
  • Expected ON voltage at lamp output: battery voltage (~12.0–14.5 V) when switched on
  • Typical current draw: depends on lamp type — incandescent lamps may draw several hundred mA; LEDs usually draw
  • If shorted to battery, output will show continuous ~12 V when lamp should be off

Diagnostic algorithm

  1. Retrieve all related DTCs and vehicle-specific data; note conditions when DTC set (hood position, ignition state).
  2. Visually inspect lamp assembly, connector, and wiring looms for damage, corrosion, or aftermarket splices; repair obvious damage.
  3. With ignition off, disconnect the underhood lamp connector. Clear codes, then cycle hood/ignition to see if DTC returns. If no return, fault likely in lamp/connector.
  4. Measure voltage at the lamp connector (harness side) with connector disconnected: - If ~12 V when it should be off, there is a short to battery upstream (harness or module). - If ~0 V, reconnect and measure at lamp side; if lamp is shorted, it will pull the circuit.
  5. Check continuity between the lamp output pin and battery positive (fused circuits) with ignition off; continuity indicates a short/backfeed. Also check continuity to ground to rule out short to ground.
  6. Isolate sections of harness (disconnect other downstream connectors, remove body panels) to locate the short. Use a fused jumper or current-limited bench supply when probing to avoid damage.
  7. If harness and lamp test good and short remains at module output, suspect internal BCM/body control module failure; verify power/ground/relevant inputs and replace module only after confirming harness is not shorted.
  8. After repair, clear codes and verify normal operation across multiple cycles and that no parasitic drain remains.

Likely causes

  • Chafed harness where lamp feed contacts a battery hot feed or fused hot cable
  • Connector corrosion at lamp or junction causing bridging to battery feed
  • Lamp assembly wiring shorted to constant hot (e.g., fused accessory circuit)
  • BCM/output driver failed closed and sourcing battery voltage

Fault status

⚠️ Status
Body module detected underhood lamp output is shorted to battery voltage (output is seeing constant battery feed or an internal short to B+). This can cause the lamp to remain on, blow fuses, or create parasitic battery drain. Investigation of lamp, harness and module required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

B2491 B2500 B2540 B2620
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