Code
B2477
HUMMER
B — Body
Reverse Lamp Relay Shorted to Ground
Views:
UK: 16
EN: 33
RU: 23
AI status
Completed
Completed
100%
Causes
- Damaged wiring harness (abrasion, pinched wire) to the reverse lamp relay
- Relay contact or coil internally shorted to ground
- Corroded or shorted relay socket/connector
- Aftermarket trailer/auxiliary lighting tied into reverse lamp circuit
- Body Control Module (BCM) driver fault
Symptoms
- Reverse lamps may be inoperative or remain on continuously
- Blown fuse(s) for reverse lamp circuit
- Related systems (backup camera/guidelines or sensors) may report faults
- Possible battery drain if lamps remain on
What to check
- Visual inspection of wiring, connectors, and relay socket for damage or corrosion
- Check fuse(s) related to reverse lamps and relay coil
- Verify whether aftermarket trailers or harnesses are connected; disconnect and retest
- Scan tool: attempt to command reverse lamp relay on/off and observe response
- Measure voltage and continuity at relay socket pins with connector disconnected
Signal parameters
- Expected: Relay control circuit should be open/high (approx battery voltage through coil feed) when not energized and switch to low (near 0 V) or ground when commanded ON if BCM grounds the coil
- Alternate design: BCM may supply positive to energize the coil — then expected is 0 V when off and battery voltage when ON. Verify vehicle wiring before trusting polarity.
- With relay removed, continuity to chassis ground on the control pin should be high/infinite (no short) with ignition off
- When commanded ON with a scanner, control pin should change state (voltage toggles) indicating driver action
Diagnostic algorithm
- Retrieve freeze frame/live data and confirm fault is current. Note any related codes.
- Visual inspection: check wiring from BCM/relay to rear lamps for chafing, pinch points, repair patches, or corrosion. Inspect connectors and relay socket.
- Disconnect any aftermarket trailer harness or adapters. Clear codes and re-test.
- With ignition OFF, remove the reverse lamp relay. Measure resistance between the relay control pin and chassis ground; resistance should be very high (open). If low, trace harness for short.
- With connector still disconnected, ignition ON, command the reverse lamp relay ON via a scan tool while measuring voltage at the control pin to verify the BCM driver changes state (either to ground or to battery voltage depending on design).
- If control pin is stuck at ground when it should be open, isolate by unplugging in-line connectors starting at the rear lamps and moving toward the relay/BCM until the short disappears. Repair damaged wire or splice.
- Swap the relay with a known-good relay of the same type (if accessible) to rule out internal relay short.
- If wiring and relay are good but control still shorted, suspect BCM driver failure. Confirm by isolating harness and performing continuity and voltage checks per manufacturer procedure before replacing BCM.
- After repair, reassemble, clear codes, verify operation by commanding reverse lamp and physically confirming lamp function and that code does not return.
Likely causes
- Chafed wire contacting chassis ground behind bumper or in trunk area
- Water intrusion / corrosion at relay connector or inline splice
- Faulty relay with internal short
- Improperly installed trailer wiring or reverse lamp adapter grounded to chassis
- Intermittent BCM ground driver failure
Fault status
Status
Reverse Lamp Relay circuit is shorted to ground — control circuit is seeing an unexpected low (ground) condition.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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