B2501

Step 1: Perform visual inspection of the left front low beam bulb. Remove bulb and check for broken filament, blackened glass, or physical damage. Inspect bulb socket for corrosion, melting, or damage. Test bulb continuity with multimeter if condition is unclear.

Step 2: Inspect headlight connector at the lamp assembly. Check for corrosion, pushed-back pins, moisture intrusion, or damaged terminals. Wiggle connector while observing for intermittent operation. Clean connectors with electrical contact cleaner if corrosion is present.

Step 3: Using a multimeter, backprobe the headlight connector with low beam commanded ON. Verify battery voltage (12-14V) is present at the power supply pin. Check ground circuit for less than 0.5 ohms resistance to chassis ground. If voltage or ground is missing, trace wiring back toward BCM.

Step 4: If power and ground are present at the connector, substitute a known-good bulb to confirm original bulb failure. If bulb tests good but circuit still fails, check for high resistance in socket contacts or wiring. Measure voltage drop across each connection point (should be less than 0.2V).

Step 5: If all wiring, connections, and bulb test good, use scan tool to command left low beam ON/OFF while monitoring BCM output driver status. Compare amperage draw to manufacturer specifications (typically 4-6 amps for halogen, less for LED/HID). Abnormal readings indicate BCM internal failure.