B2489

Code

Other B — Body

UNDERHOOD LAMP OUTPUT CIRCUIT Failure

Brand: Other

Type: B — Body

Views: UK: 20 EN: 21 RU: 26

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Blown fuse or faulty relay protecting the underhood lamp circuit
Burned out or disconnected underhood lamp (bulb or LED module)
Open or shorted wiring, damaged harness or pinched cable to lamp
Corroded or loose connector at lamp or BCM
Faulty hood switch or lamp switch input
Faulty BCM or output driver transistor

Symptoms

Underhood/engine compartment lamp does not illuminate when hood is opened
Underhood lamp stays on continuously (possible battery drain)
DTC B2489 stored in BCM and lamp-related warning or message may be displayed
Intermittent lamp operation or flicker
Possible parasitic battery drain when vehicle is off

What to check

Scan tool: read DTCs, freeze frame, and lamp status; check for additional related body codes
Visual inspection: lamp lens, socket, wiring harness routing, and connectors for damage or corrosion
Check relevant fuse(s) and any relay; verify fuse is correct rating and not blown
Operate hood switch and observe lamp; try manually applying 12V to lamp to confirm lamp condition
Measure voltage at lamp connector with hood open (when lamp commanded on) and with connector disconnected
Measure continuity and resistance between lamp connector and BCM output pin, and to ground

Signal parameters

Expected battery voltage (~12–14.5 V) present at lamp connector when lamp commanded ON (may be PWM for LED lamps)
Near 0 V or open-circuit when lamp commanded OFF (if output is ground-switched or power-switched, behavior will depend on circuit type)
Typical current draw: incandescent lamps often 0.3–2.0 A; LED modules typically
Continuity between lamp and BCM output when connector connected (low ohms); open-circuit indicates break
No persistent short to ground (very low resistance to ground with connector disconnected indicates short)

Diagnostic algorithm

Retrieve and record all stored DTCs and freeze-frame data with scan tool. Note lamp state and battery voltage at fault time.
Attempt to reproduce fault by operating hood switch and observing lamp function and scan tool live data for the underhood lamp output.
Perform a visual inspection of the lamp, lens, socket, wiring harness, and connectors for damage, corrosion, or loose pins.
Check fuse(s) and any relay protecting the circuit; replace blown fuses only after finding root cause of failure.
With connector at lamp disconnected, apply 12 V to lamp terminals to verify lamp/bulb/LED module illuminates. If lamp fails, replace lamp module.
With a DVOM, measure voltage at the lamp connector while commanding the lamp ON from scan tool or by opening hood. Compare to battery voltage and expected behavior (steady vs. PWM).
Check continuity between the lamp connector and the BCM output pin using the wiring diagram. Repair any open circuits, damaged wires or connectors found.
If voltage is present at the lamp connector but lamp does not light and lamp tests good, check for poor ground at lamp or high-resistance connections.
With connector disconnected, test for short-to-ground or short-to-battery by measuring resistance from the BCM output to ground and to battery positive. Very low resistance indicates short.
Wiggle test harness while monitoring voltage/current to reproduce intermittent faults. Inspect areas where harness passes through body panels or near moving parts for chafing.
If wiring, connector, lamp and fuses are good but output behavior is abnormal, check BCM outputs with scope or consult manufacturer service data for expected PWM patterns. Replace BCM only after confirming external circuit integrity.
After repair, clear codes and retest operation for several cycles. Verify no parasitic draw and that DTC does not return.