Code
B2142
HUMMER
B — Body
Mirror Left Control Switch Circuit Malfunction
AI status
Completed
Completed
100%
Causes
- Blown fuse or popped circuit protection for mirror circuit
- Damaged or chafed wiring in door harness (common at door hinge/boot)
- Corroded or loose connector pins at mirror, switch, or body control module (BCM)
- Failed left mirror control switch (internal contact wear or water intrusion)
- Failed mirror motor or internal short in mirror assembly
- Faulty BCM or module input circuit
Symptoms
- Left exterior mirror does not respond to adjustment commands
- Intermittent or erratic mirror movement (works only sometimes or in certain door positions)
- Mirror stuck in one position
- Possible fuse blow when attempting to operate mirror
- No change after switch operation; other door electrical functions may be unaffected
What to check
- Scan vehicle for B2142 and any related codes; record freeze-frame data and clear then retest
- Verify ignition/key in correct position and attempt mirror adjustment while observing behavior
- Inspect related fuses and circuit breakers for the mirror circuit
- Visually inspect connectors at the mirror, door switch, and BCM for corrosion, bent pins, or water
- Perform a wiggle test on the door harness while operating the switch to check for intermittent wiring faults
- Backprobe switch and connector pins to verify reference voltage and outputs
Signal parameters
- Reference supply to mirror switch: ~12 V with ignition/accessory ON (may be fused)
- Switch outputs: toggle between ~0 V (ground) and battery voltage (~12 V) or pull to ground depending on circuit design
- Motor drive current: typically up to a few amps when operating (varies by model)
- Switch contact resistance: low (near 0–5 Ω) when closed; open circuit when not activated
- Expected continuity from switch output to mirror motor when actuated; open/infinite if wiring broken
Diagnostic algorithm
- Read and record all stored codes. Clear codes and attempt to reproduce B2142 to confirm active fault.
- Check fuses and circuit protection for the mirror/mirror switch circuit; replace if blown and retest.
- Operate left mirror switch while observing operation. Note if any positions work or if fuse blows.
- Visually inspect connectors and wiring at the mirror, door jamb, and switch. Look for pin corrosion, pulled wires, crushed sections, or water entry.
- With ignition ON, backprobe the mirror switch connector: verify reference (battery) supply and ground. Compare to known-good values (approx. 12 V supply, ground continuity).
- Activate each switch direction and measure the switch output pins for expected voltage change. If outputs do not change, suspect the switch or BCM input.
- If switch outputs are present, backprobe at the mirror connector to confirm the motor receives voltage when switch is operated. If motor receives proper voltage but does not move, bench-test/apply 12 V directly to motor to verify motor condition.
- Perform a continuity check from the switch output pins to the mirror motor pins with connectors disconnected. Repair any open circuits or high-resistance connections.
- If wiring and motor check good but fault persists, bench-test or replace the left mirror control switch. If replacement does not clear the fault, consider BCM input circuit testing or replacement.
- After repair, clear codes and verify mirror operation over multiple door positions and after several cycles. Reinspect for intermittent faults (wiggle test).
Likely causes
- Broken/chafed wiring in the door jamb harness causing open/short when door moves
- Corroded/loose connector at the mirror or door switch
- Failed left mirror control switch assembly (most common single-part failure)
- Water intrusion into mirror housing causing intermittent shorts
- Faulty ground at door/module
Fault status
Status
B2142 - Mirror Left Control Switch Circuit Malfunction
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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Code
B2142
Other
B — Body
NVM TIC Failure
AI status
Completed
Completed
100%
Causes
- Blown fuse or popped circuit protection for mirror circuit
- Damaged or chafed wiring in door harness (common at door hinge/boot)
- Corroded or loose connector pins at mirror, switch, or body control module (BCM)
- Failed left mirror control switch (internal contact wear or water intrusion)
- Failed mirror motor or internal short in mirror assembly
- Faulty BCM or module input circuit
Symptoms
- Left exterior mirror does not respond to adjustment commands
- Intermittent or erratic mirror movement (works only sometimes or in certain door positions)
- Mirror stuck in one position
- Possible fuse blow when attempting to operate mirror
- No change after switch operation; other door electrical functions may be unaffected
What to check
- Scan vehicle for B2142 and any related codes; record freeze-frame data and clear then retest
- Verify ignition/key in correct position and attempt mirror adjustment while observing behavior
- Inspect related fuses and circuit breakers for the mirror circuit
- Visually inspect connectors at the mirror, door switch, and BCM for corrosion, bent pins, or water
- Perform a wiggle test on the door harness while operating the switch to check for intermittent wiring faults
- Backprobe switch and connector pins to verify reference voltage and outputs
Signal parameters
- Reference supply to mirror switch: ~12 V with ignition/accessory ON (may be fused)
- Switch outputs: toggle between ~0 V (ground) and battery voltage (~12 V) or pull to ground depending on circuit design
- Motor drive current: typically up to a few amps when operating (varies by model)
- Switch contact resistance: low (near 0–5 Ω) when closed; open circuit when not activated
- Expected continuity from switch output to mirror motor when actuated; open/infinite if wiring broken
Diagnostic algorithm
- Read and record all stored codes. Clear codes and attempt to reproduce B2142 to confirm active fault.
- Check fuses and circuit protection for the mirror/mirror switch circuit; replace if blown and retest.
- Operate left mirror switch while observing operation. Note if any positions work or if fuse blows.
- Visually inspect connectors and wiring at the mirror, door jamb, and switch. Look for pin corrosion, pulled wires, crushed sections, or water entry.
- With ignition ON, backprobe the mirror switch connector: verify reference (battery) supply and ground. Compare to known-good values (approx. 12 V supply, ground continuity).
- Activate each switch direction and measure the switch output pins for expected voltage change. If outputs do not change, suspect the switch or BCM input.
- If switch outputs are present, backprobe at the mirror connector to confirm the motor receives voltage when switch is operated. If motor receives proper voltage but does not move, bench-test/apply 12 V directly to motor to verify motor condition.
- Perform a continuity check from the switch output pins to the mirror motor pins with connectors disconnected. Repair any open circuits or high-resistance connections.
- If wiring and motor check good but fault persists, bench-test or replace the left mirror control switch. If replacement does not clear the fault, consider BCM input circuit testing or replacement.
- After repair, clear codes and verify mirror operation over multiple door positions and after several cycles. Reinspect for intermittent faults (wiggle test).
Likely causes
- Broken/chafed wiring in the door jamb harness causing open/short when door moves
- Corroded/loose connector at the mirror or door switch
- Failed left mirror control switch assembly (most common single-part failure)
- Water intrusion into mirror housing causing intermittent shorts
- Faulty ground at door/module
Fault status
Status
B2142 - Mirror Left Control Switch Circuit Malfunction
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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