Code
B2472
HUMMER
B — Body
Low Beam Fault
AI status
Completed
Completed
100%
Causes
- Burned or failed low-beam bulb (halogen, HID ballast, or LED module)
- Blown fuse or faulty headlamp relay
- Poor/ corroded connector or socket at the lamp
- Damaged wiring (open, short to ground or power, chafe)
- Faulty headlamp driver, ballast or LED driver module
- Body Control Module (BCM) or headlamp control module fault
Symptoms
- One or both low-beam headlights inoperative
- Headlamps flicker or work intermittently
- Instrument cluster warning or message for headlamp
- Reduced nighttime illumination or asymmetric beam
- Other modules report related communication faults (occasional)
What to check
- Use a scan tool to read B2472 and any related freeze-frame or module data
- Visually inspect bulbs, sockets and headlamp lenses for damage or moisture
- Check fuses and relays for the headlamp circuits
- Inspect connectors for corrosion, bent pins, or poor contact
- Measure voltage and ground at the headlamp connector with lamp commanded ON
- Perform wiggle test on wiring and connectors while watching live data/lamps
Signal parameters
- Battery supply at lamp connector (engine off/on): ~12.0–14.5 V
- Typical halogen low-beam current: ~3–6 A (55 W class) — expect ~3–5 A at 13.5 V
- Typical halogen filament resistance (hot): ~2–5 Ω (varies by bulb type)
- LED driver input current: can be ~0.5–5 A depending on module (check OEM spec)
- Ground resistance to chassis:
- If PWM dimming used: control signal frequencies commonly 100–1000 Hz (module-specific)
Diagnostic algorithm
- Safety: park, key OFF, wear eye protection for bulb handling. Use a scan tool with module access.
- Capture data: record freeze-frame and related codes. Note which side (LH/RH) is affected if indicated.
- Visual: inspect lamp assembly for burned bulb, water ingress, or connector damage. Replace visibly damaged components.
- Bulb check: remove and visually inspect filament (halogen) or test replacement with a known-good bulb or swap left/right to see if fault follows bulb.
- Fuses/relays: verify headlamp fuses and relays. Replace suspect items and retest.
- Measure supply: command low beams ON with scan tool; measure voltage at the lamp power pin and ground. Expect battery voltage. If no voltage, trace back to relay/BCM.
- Ground and continuity: check continuity from lamp ground to chassis ground (
- Wiring inspection: inspect harness for chafe or pinched areas, especially near hinges, bumper, or lamp mount. Repair shorts/opens.
- Module output: if voltage present at relay but not at lamp, test BCM/headlamp driver output. Check for PWM or switched output using scope if available.
- Communications: verify module communications (CAN/serial) with scan tool; address U-codes that may indicate lost comms to BCM or headlamp module.
- Component substitution: if wiring, fuses and bulbs are good and BCM/driver output is abnormal, replace or reprogram the headlamp driver or BCM per OEM procedure.
- Clear codes and road-test: after repairs, clear codes, operate headlamps through all modes, and verify B2472 does not return.
Likely causes
- Failed low-beam bulb or poor bulb contact
- Corroded/loose lamp connector or ground
- Blown fuse or faulty relay for headlamps
- Wiring damage at harness near lamp or hinge areas
- Faulty headlamp driver module (if vehicle uses HID/LED)
Fault status
Status
Body module reports LOW BEAM FAULT — circuit open/short/overload or headlamp driver/communication fault detected.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
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Repair manuals
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