Code
B2470
HUMMER
B — Body
Daytime Running Lamps Fault
AI status
Completed
Completed
100%
Causes
- Burned-out DRL bulbs or failed LED modules
- Blown fuse or faulty DRL relay/module
- Open, shorted or corroded wiring/connectors in the DRL circuit
- Poor or missing ground at lamp/module
- Faulty BCM or headlamp/DRL control module
- Loss of communication on CAN/bus between BCM and lamp module
Symptoms
- Daytime running lamps do not illuminate
- DRLs operate intermittently or flicker
- DRLs remain on constantly or do not dim with other lights
- Instrument cluster or dash message indicating DRL fault
- Related headlamp or exterior lighting anomalies
What to check
- Use a scan tool to read B2470 and any other stored codes; view freeze-frame and live data (DRL status, voltage, commanded state)
- Visually inspect DRL bulbs/LED modules and lamp lenses for damage
- Check DRL fuse(s) and any relays; replace if blown/defective
- Inspect wiring and connectors for corrosion, damage, or loose terminals at lamps and BCM
- Verify good ground(s) at lamp/module (measure
- Measure supply voltage at the lamp/module with DRL commanded on (should be battery voltage ~11–14 V)
Signal parameters
- Supply voltage to DRL lamp/module: ~11–14 V with engine/run as required
- Ground continuity: near 0 Ω from lamp ground to chassis
- Lamp current (typical): halogen DRL ~1–5 A, LED modules lower — consult vehicle spec
- PWM control (if used): frequency often 100–1000 Hz with variable duty cycle; duty changes with command
- BCM status: DRL command = ON/OFF in live data; compare command to actual lamp voltage/current
- Expected CAN messages: module alive and responding (no U-codes)
Diagnostic algorithm
- Confirm complaint and key-on/engine-run conditions that enable DRL operation per vehicle manual.
- Connect a scan tool. Read and record B2470 and any additional DTCs. Check live data for DRL command, lamp voltage, and current.
- Inspect lamps and sockets. Replace visibly damaged bulbs/LED modules and retest.
- Check fuses and relays for the DRL circuit; substitute a known-good relay if suspect.
- With DRL commanded ON, measure battery voltage at the lamp power pin and measure voltage drop to ground. Diagnose open/high resistance if voltage is low or absent.
- Measure lamp current or ballast resistance to verify load is within specification. An open or shorted load may set the code.
- Inspect and wiggle wiring harness and connectors while monitoring live data for intermittent faults; repair any corrosion or damaged wires.
- Verify grounds: clean, tighten, and recheck resistance to chassis.
- If wiring and lamps are good but fault persists, check BCM/module outputs and communication. Test for CAN-bus errors and verify module presence.
- If module output is faulty and wiring/load are good, consider replacing the lamp control module/BCM or updating software per service information. Clear codes and verify proper operation under all DRL conditions.
- After repair, erase codes and perform full system check and road test to confirm the repair; monitor for code return.
Likely causes
- Failed DRL lamp (bulb or LED module)
- Corroded/loose connector or poor ground at lamp
- Blown fuse or defective DRL relay/module
- Open/short in power or return wiring
- Faulty BCM or module software/firmware issue
Fault status
Status
Stored DTC B2470: Daytime Running Lamps Fault — the DRL circuit is reporting a fault (open/short/load/communication).
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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Repair manuals
Manual library for HUMMER
138
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