B1499

Step 1: Perform visual inspection of left front and left rear turn signal lamps. Check for burnt bulbs, cracked lenses, moisture intrusion, and corrosion in bulb sockets. Remove and inspect bulbs for broken filaments.

Step 2: Using a test light or multimeter, verify power and ground at the left turn signal bulb socket while activating the turn signal. Expected reading is 12-14V on power wire when activated, and continuity to ground on ground wire.

Step 3: If power and ground are present but bulb does not illuminate, replace bulb and socket if corroded. If no power is present, trace wiring from BCM to lamp assembly checking for opens, shorts, or damaged insulation using a multimeter continuity test.

Step 4: Inspect and clean all ground connections in the left turn signal circuit, typically located at frame rails or body panels. Verify less than 0.5 ohms resistance between ground wire and chassis ground.

Step 5: If all wiring and connections test good, check BCM connector pins for corrosion or damage. Verify BCM is receiving proper input from turn signal switch and that BCM output driver is functioning by measuring voltage at BCM connector during turn signal activation.

Step 6: Clear codes and perform functional test of left turn signal operation. Monitor live data for turn signal circuit current draw (typically 1.5-3 amps per bulb) to confirm proper operation and verify code does not return.