Code
B2119
HUMMER
B — Body
Lumbar Forward/Aft Sensor Failed
Views:
UK: 10
EN: 13
RU: 9
AI status
Completed
Completed
100%
Causes
- Failed lumbar forward/aft position sensor
- Damaged or chafed wiring harness to the sensor
- Corroded, loose or pushed-back connector terminals
- Open or shorted signal, reference or ground circuit
- Faulty seat control/module or incorrect module programming
- Mechanical jam or damage to lumbar mechanism preventing sensor movement
Symptoms
- Lumbar forward/back adjustment does not operate or is unresponsive
- Lumbar position does not change even though motor runs (or motor does not run)
- One or more seat memory/adjust features may fail or not store correctly
- DTC B2119 stored in body/seat control module and lamp or message may be present on scan tool
- Intermittent lumbar operation or movement only in one direction
What to check
- Read and record all stored DTCs and freeze frame data with a factory-capable scan tool
- Verify customer complaint and attempt lumbar forward/back operation while watching live data
- Inspect fuses and power/ground to the seat control module
- Visually inspect seat wiring harness, connectors and sensor for damage or corrosion
- Wiggle the harness and connector while observing live data for intermittent faults
- Check for water stains or signs of upholstery penetration near the sensor area
Signal parameters
- Sensor uses a position feedback signal that should change smoothly as lumbar moves
- Typical reference supply: ~5 V (varies by vehicle); signal voltage should vary proportionally between ~0 and ~5 V with position
- If the circuit is resistive, resistance should vary smoothly with position rather than open or infinite
- An open circuit, short to ground/power, or a fixed/stuck voltage indicates a fault
- Diagnostic data may show erratic or no change in the sensor value during movement
Diagnostic algorithm
- Use scan tool to confirm B2119 is current or stored and note any additional seat/body codes.
- Attempt lumbar forward/back while observing live data for the lumbar sensor; note whether the signal changes.
- Perform a visual inspection of the seat, connectors and wiring for obvious damage or contamination; repair any obvious issues.
- Check power and ground at the seat control module and at the sensor connector (verify reference voltage present with ignition ON).
- Back-probe the sensor connector and measure signal voltage or resistance while operating the lumbar. A smooth changing value indicates a good sensor and wiring.
- Wiggle test the wiring and connector while observing the live signal for intermittent drops or spikes.
- If open/short is found, trace and repair the wiring harness; repair or replace damaged connector terminals as needed.
- If wiring checks good but sensor signal is fixed or out of spec, replace the lumbar forward/aft position sensor.
- If new sensor and wiring are good but code returns, test or replace the seat control/module and verify correct software/configuration.
- Clear DTCs and verify proper operation and that the code does not return after diagnosis and road/test cycles as required.
Likely causes
- Sensor internal failure (most common)
- Broken connector pins or corrosion at the seat sensor connector
- Wiring harness short to ground or open circuit between sensor and seat module
- Intermittent connection due to wire chafe/wear
- Seat control module fault or configuration issue (least common)
Fault status
Status
B2119 - Lumbar Forward/Aft Sensor Circuit Failure (position feedback fault: open, short, intermittent or out-of-range)
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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