Code
B2146
HUMMER
B — Body
Left Front Mirror Horizontal Position Sensor Circuit Low
AI status
Completed
Completed
100%
Causes
- Short to ground in the left front mirror horizontal position sensor signal wire
- Open or high-resistance ground or reference supply to the mirror sensor
- Failed horizontal position sensor inside the mirror assembly
- Corroded, damaged, or disconnected mirror connector or wiring through the door jamb
- Faulty mirror control module, door module, or body control module (less common)
- Aftermarket mirror or prior repair with incorrect wiring or damaged harness
Symptoms
- Left exterior mirror horizontal adjustment not working or limited
- Mirror position known/displayed incorrectly (if system reports position)
- Intermittent operation of mirror when door is opened/closed or when wiring is flexed
- Fault light or stored codes related to mirror/door module functions
- Possible mirror folding/unfolding faults if integrated
What to check
- Scan tool: read DTCs and live data for left mirror horizontal position sensor
- Visual inspection of left mirror connector, wiring through door hinge area, and module connectors for corrosion, pin damage, or loose pins
- Wiggle test the mirror wiring while watching live data or watching mirror operation for intermittent changes
- Backprobe mirror connector to measure reference voltage, sensor output, and ground with ignition ON (or per service manual)
- Measure continuity and check for short to ground between signal wire and chassis with ignition OFF
- Check associated ground(s) for good continuity to chassis and battery negative
Signal parameters
- Typical sensor reference: +5 V reference from control module (verify exact value in service manual)
- Expected sensor output: 0–5 V proportional to mirror horizontal position; mid-position typically ≈ 2.5 V
- Low/fault indication: sensor output near 0 V (example:
- Open circuit: no reference or output (no voltage present)
- Potentiometer resistance range (varies by design): commonly a few hundred ohms to several kiloohms — check service manual for exact ohms
Diagnostic algorithm
- Connect a scan tool and confirm B2146 is active. Note freeze frame and live sensor voltage/position data.
- Visually inspect the left mirror, harness entry at the door, and connector for damage, moisture, or corrosion. Repair visible damage.
- With ignition ON (accessory), backprobe the mirror connector: verify 5 V reference (or specified reference) present, good ground, and measure the horizontal position sensor output voltage.
- If reference voltage is present but output is low (
- Perform continuity checks from the mirror connector back to the mirror control/door module connector. Repair any opens or shorts found. Pay attention to wiring through the door hinge — flex the harness to reproduce faults.
- If wiring and connectors test OK and reference is present, bench-test or replace the mirror assembly (or remove mirror trim to access sensor) and re-measure sensor output across positions. If the internal sensor is out of specification, replace the mirror assembly.
- If mirror and harness are good but issue persists, inspect and test the controlling module (driver door module / body control module) output/reference for faults and reprogram/replace as recommended by the manufacturer.
- After repair, clear codes and perform functional test and road/door-cycle test to ensure the fault does not return.
Likely causes
- Wiring chafed in door jamb causing short to chassis ground when door moves
- Connector pins corroded or pushed out at mirror or door module
- Mirror assembly internal potentiometer failed (wear/contamination)
- Blown/dirty ground or 5V reference feed at mirror connector
- Mirror replacement or collision damage with miswired harness
Fault status
Status
Left front exterior mirror horizontal position sensor circuit is reporting a low-voltage condition (signal near ground), indicating a possible short to ground, failed sensor, or wiring/connector fault.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
Similar codes
Repair manuals
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Code
B2146
Other
B — Body
Seat Recline Motor Position Out of Range
AI status
Completed
Completed
100%
Causes
- Short to ground in the left front mirror horizontal position sensor signal wire
- Open or high-resistance ground or reference supply to the mirror sensor
- Failed horizontal position sensor inside the mirror assembly
- Corroded, damaged, or disconnected mirror connector or wiring through the door jamb
- Faulty mirror control module, door module, or body control module (less common)
- Aftermarket mirror or prior repair with incorrect wiring or damaged harness
Symptoms
- Left exterior mirror horizontal adjustment not working or limited
- Mirror position known/displayed incorrectly (if system reports position)
- Intermittent operation of mirror when door is opened/closed or when wiring is flexed
- Fault light or stored codes related to mirror/door module functions
- Possible mirror folding/unfolding faults if integrated
What to check
- Scan tool: read DTCs and live data for left mirror horizontal position sensor
- Visual inspection of left mirror connector, wiring through door hinge area, and module connectors for corrosion, pin damage, or loose pins
- Wiggle test the mirror wiring while watching live data or watching mirror operation for intermittent changes
- Backprobe mirror connector to measure reference voltage, sensor output, and ground with ignition ON (or per service manual)
- Measure continuity and check for short to ground between signal wire and chassis with ignition OFF
- Check associated ground(s) for good continuity to chassis and battery negative
Signal parameters
- Typical sensor reference: +5 V reference from control module (verify exact value in service manual)
- Expected sensor output: 0–5 V proportional to mirror horizontal position; mid-position typically ≈ 2.5 V
- Low/fault indication: sensor output near 0 V (example:
- Open circuit: no reference or output (no voltage present)
- Potentiometer resistance range (varies by design): commonly a few hundred ohms to several kiloohms — check service manual for exact ohms
Diagnostic algorithm
- Connect a scan tool and confirm B2146 is active. Note freeze frame and live sensor voltage/position data.
- Visually inspect the left mirror, harness entry at the door, and connector for damage, moisture, or corrosion. Repair visible damage.
- With ignition ON (accessory), backprobe the mirror connector: verify 5 V reference (or specified reference) present, good ground, and measure the horizontal position sensor output voltage.
- If reference voltage is present but output is low (
- Perform continuity checks from the mirror connector back to the mirror control/door module connector. Repair any opens or shorts found. Pay attention to wiring through the door hinge — flex the harness to reproduce faults.
- If wiring and connectors test OK and reference is present, bench-test or replace the mirror assembly (or remove mirror trim to access sensor) and re-measure sensor output across positions. If the internal sensor is out of specification, replace the mirror assembly.
- If mirror and harness are good but issue persists, inspect and test the controlling module (driver door module / body control module) output/reference for faults and reprogram/replace as recommended by the manufacturer.
- After repair, clear codes and perform functional test and road/door-cycle test to ensure the fault does not return.
Likely causes
- Wiring chafed in door jamb causing short to chassis ground when door moves
- Connector pins corroded or pushed out at mirror or door module
- Mirror assembly internal potentiometer failed (wear/contamination)
- Blown/dirty ground or 5V reference feed at mirror connector
- Mirror replacement or collision damage with miswired harness
Fault status
Status
Left front exterior mirror horizontal position sensor circuit is reporting a low-voltage condition (signal near ground), indicating a possible short to ground, failed sensor, or wiring/connector fault.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
Similar codes
Repair manuals
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