Code
B2149
HUMMER
B — Body
Right Front Mirror Vertical Position Sensor Circuit High
AI status
Completed
Completed
100%
Causes
- Short to battery (voltage) on the mirror vertical position sensor signal circuit
- Open or high-resistance ground or reference circuit
- Corroded or loose connector at the mirror or harness
- Water intrusion or physical damage to the mirror assembly
- Failed vertical position sensor inside the mirror
- Faulty body control module (BCM) or mirror control module (if equipped)
Symptoms
- Right front mirror will not move or will not move correctly in the vertical direction
- Mirror may move erratically or move only in one direction
- One or more stored DTCs related to mirror position or mirror circuit
- Possible mirror warning or message on the instrument cluster (model dependent)
- Reduced or no memory position recall for the passenger mirror
What to check
- Connect a scan tool, verify B2149 is active or stored, note freeze frame/live data if available
- Visually inspect the right front mirror housing and wiring harness for damage, corrosion, or water intrusion
- Check the mirror connector pins for bent pins, corrosion, pushed-out pins, or contamination
- Operate mirror vertical adjustment while watching live data for the position sensor signal and voltage reference
- Measure reference voltage (usually 5V) and ground continuity at the mirror connector with key on
- Check for short to battery on the sensor signal wire (measure voltage with circuit idle and while actuating)
Signal parameters
- Reference voltage: nominally around 5.0 V (varies by vehicle) — present with key ON
- Signal voltage: expected to vary within ~0.5–4.5 V as mirror moves vertically (position dependent)
- Short to battery: signal rail near battery voltage (~12 V) or stuck >5 V
- Short to ground: signal near 0 V and not changing with adjustment
- Ground continuity: mirror ground to chassis
- Connector pin voltage with key ON and mirror at rest: reference ~5 V, signal within expected idle range
Diagnostic algorithm
- Verify code: Use a scan tool to confirm B2149 is present. Clear codes and see if it returns while reproducing the concern.
- Inspect mirror and harness: Visually inspect the right front mirror, connector, and harness for physical damage, corrosion, or water entry. Repair or reseal as needed.
- Check connector: Disconnect the mirror connector and inspect pins. Clean and repair any corrosion or bent pins. Reconnect and recheck for codes.
- Measure reference and signal voltages: Backprobe the mirror connector with the ignition ON. Confirm the reference (typically 5V) and the signal voltage. If signal is near battery voltage, suspect short to 12V; if near 0V, suspect short to ground or open reference.
- Operate mirror while monitoring: Command mirror up/down and watch the signal voltage change. If the signal does not change or is out of range, the sensor or connector/harness is suspect.
- Check grounds and continuity: Verify mirror ground to chassis and continuity of signal/ref wires to the BCM. Repair any high resistance or open circuits.
- Isolate harness: If wiring checks are inconclusive, disconnect mirror and measure resistance of the signal wire to power/ground to locate shorts. Repair wiring or replace harness as required.
- Swap or bench-test mirror assembly: If available, install a known-good right mirror or bench-test the mirror assembly to confirm sensor operation. If the replacement fixes the issue, replace the mirror assembly.
- Check BCM/mirror control module: If wiring and mirror test good, inspect BCM connectors and replace or reflash BCM/mirror control module only after wiring and sensor are verified good.
- Clear codes and verify repair: After repair, clear DTCs, exercise mirror through full range multiple times and confirm the code does not return.
Likely causes
- Corroded/loose connector at right front mirror causing intermittent high voltage reading
- Short to 12V in the sensor signal or reference feed due to chafed harness
- Failed vertical position potentiometer/position sensor inside mirror assembly
- Poor ground on mirror assembly causing abnormal sensor reference voltages
Fault status
Status
Right Front Mirror Vertical Position Sensor Circuit High — signal above expected range; possible short to battery, sensor fault, or wiring/connector issue.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Repair manuals
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