Code
B2107
HUMMER
B — Body
Front Vertical Down Switch Failed
AI status
Completed
Completed
100%
Causes
- Failed or worn front vertical down switch
- Open or short in switch wiring or connector (corrosion, pin damage)
- Poor or missing ground or reference voltage to the switch
- Intermittent connector contact or water intrusion
- Failed front vertical actuator mechanically preventing switch operation
- Faulty control module (rare) or incorrect module programming
Symptoms
- Stored B2107 DTC (may set lamp/message depending on system)
- Associated function (e.g., leveling, seat, step or actuator movement) fails to complete or does not move to down position
- Intermittent operation of the affected vertical movement
- Possible diagnostic or system fault messages in vehicle information display
What to check
- Retrieve DTCs and freeze frame with a scan tool; note related codes or network communication errors
- Check service information for exact switch location and wiring diagram
- Visual inspection of the switch, actuator and harness for damage, corrosion, water intrusion or loose connectors
- Operate the affected system while observing switch/connector for visible movement or damage
- Backprobe the switch connector and measure reference voltage, signal voltage and ground with a multimeter
- Check continuity and resistance of the switch circuit between switch and module with harness disconnected
Signal parameters
- Reference voltage to switch: typically 5 V DC (verify with vehicle wiring diagram)
- Switch actuated (down): signal should change state—either to near 0 V (ground) or to battery voltage depending on circuit design
- Switch not actuated (up): opposite state to the actuated condition
- Expected continuity: closed when actuated or specified resistance per OEM spec
- No voltage fluctuations or intermittent drops when operating the system
Diagnostic algorithm
- Verify the customer concern and re-scan all modules; record B2107 and any related codes. Clear codes and attempt to re-create the fault. 2) Locate the front vertical down switch and obtain the wiring diagram and connector pinouts from service literature. 3) Perform a visual inspection of the switch, actuator, and harness for physical damage, corrosion or water entry. Repair any obvious problems. 4) With harness connected, backprobe the switch connector. Verify reference voltage (usually 5 V) and ground presence. Operate the mechanism and observe the switch signal for the expected change. 5) If reference voltage or ground is missing, trace and repair the wiring back to the controlling module; check module connectors. 6) If reference/ground are correct but the switch signal does not change correctly, disconnect switch and check for correct resistance/continuity across switch terminals per OEM spec. Replace switch if out of specification. 7) If switch tests good and wiring is continuous, check for short to battery or ground in the signal wire; repair as needed. 8) If wiring and switch are good but code remains, test the module input for proper response or consider module programming/repair as a last step. 9) After repairs, clear codes and verify proper operation and that B2107 does not return.
Likely causes
- Switch contacts stuck or burnt
- Connector corrosion or bent pins at the switch or at the module harness
- Broken wire, chafed insulation, or short to battery/ground in the switch circuit
- Missing 5V reference or ground from the controlling module
- Mechanical binding of the actuator preventing switch actuation
Fault status
Status
Front vertical down switch circuit fault detected. Inspect switch, wiring and module input.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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