Code
B2151
HUMMER
B — Body
Right Front Mirror Horizontal Position Sensor Circuit High
AI status
Completed
Completed
100%
Causes
- Open or damaged wiring in the right front mirror horizontal position sensor circuit
- Short to battery voltage on the sensor signal wire
- Corroded/loose connector or bent terminal at the mirror or body harness
- Failed position sensor inside the mirror assembly
- Faulty mirror control module / body control module (BCM)
- Water intrusion in mirror causing intermittent shorts
Symptoms
- Right exterior mirror will not adjust horizontally or moves erratically
- Mirror position memory may not work for the right side
- DTC B2151 stored and may illuminate a body/system warning depending on vehicle
- Mirror may be stuck at one position and not respond to switch
- Intermittent operation of mirror functions, especially after door movement or moisture
What to check
- Retrieve B2151 and any related mirror/BCM codes with a scan tool; note freeze-frame/live data
- Visually inspect right mirror connector, wiring through the door hinge and door jamb, and mirror housing for damage or moisture
- Backprobe the mirror signal connector with ignition ON and operate the mirror while watching live data
- Measure reference (5V) and ground at the mirror connector with a digital multimeter
- Check continuity and for shorts to battery and ground on the signal wire (with power off where required)
- Wiggle test the harness while monitoring the signal; check for intermittent changes
Signal parameters
- Reference voltage (mirror module): ~5.0 V (nominal)
- Position sensor signal typical range: approximately 0.1 V to 4.9 V depending on mirror angle
- Circuit high condition: signal > ~4.7–5.0 V or near battery voltage
- Expected change: signal should vary smoothly when commanding horizontal mirror movement
Diagnostic algorithm
- Confirm code presence and any related codes; note whether code is Current or Intermittent.
- Perform a visual inspection of the right mirror assembly, connector, and harness through the door hinge for chafing, pin damage, or moisture.
- With ignition ON (accessory), backprobe the mirror signal, reference, and ground wires at the mirror connector. Verify reference ≈5 V and good ground.
- Command horizontal mirror movement while observing the sensor signal. The signal should change smoothly; if it remains high, suspect open/short or sensor fault.
- If signal is high at the mirror connector, disconnect the mirror and check the connector pins for corrosion or a short to Vb on the vehicle harness side.
- With mirror disconnected, check continuity from the module connector to the mirror connector for the signal wire; check for short to battery and to ground.
- Repair any wiring faults (repair/replace damaged section, clean or replace connector pins, apply dielectric grease).
- If wiring and connector are good and signal is still invalid, replace the mirror assembly (contains the position sensor).
- If new mirror does not clear the code, investigate the mirror control module/BCM outputs and wiring at the module; consult service manual pinouts and perform module-level diagnostics.
- After repair, clear codes and confirm proper mirror operation and that B2151 does not return during functional test and vehicle use.
Likely causes
- Connector pin corrosion at the mirror (common after water exposure)
- Broken/displaced signal wire where it passes through the door hinge
- Sensor internal failure causing incorrect output
- Aftermarket accessories or previous door repairs that disturbed the harness
- Poor ground or missing reference voltage to the mirror module (less common)
Fault status
Status
Right Front Mirror Horizontal Position Sensor Circuit High — signal voltage above expected range. Possible open circuit or short to battery; mirror may not adjust horizontally.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
HUMMER
-
HUMMER: 2009
-
HUMMER: 2008
-
HUMMER: 2007
-
HUMMER: 2005
-
HUMMER: 2004
-
HUMMER: 2000
-
HUMMER: 1999
-
HUMMER: 1994
-
HUMMER: 1993
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email