B2489

Step 1: Perform visual inspection of underhood lamp assembly, checking for obvious bulb failure, physical damage, water intrusion, or melted components. Remove and inspect bulb for filament continuity if applicable.

Step 2: Using a digital multimeter, test for battery voltage at the underhood lamp connector with hood open and ignition on. Expected reading should be 12-14V on power supply wire. If no voltage present, trace wiring back toward BCM for opens or damage.

Step 3: Test lamp ground circuit by measuring resistance from lamp ground terminal to known good chassis ground. Should read less than 1 ohm. High resistance indicates poor ground connection or damaged ground wire.

Step 4: With lamp disconnected, measure resistance of lamp circuit from BCM connector to lamp connector. Should be less than 5 ohms for power and ground circuits. Excessive resistance indicates damaged wiring or corroded connections.

Step 5: If all wiring and connections test good, install known-good underhood lamp assembly and retest. If fault persists, suspect BCM output driver failure and perform BCM output test using bi-directional controls if available.

Step 6: Clear code, cycle hood open/closed multiple times with ignition on, and verify underhood lamp operation. Rescan for codes to confirm repair and proper circuit operation.