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Home / DTC / B1A14 — Keyless/KOS key 5 low battery

B1A14 — Keyless/KOS key 5 low battery

Detailed page for trouble code B1A14.

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Code

B1A14

MITSUBISHI B — Body

Keyless/KOS key 5 low battery

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Weak or depleted coin-cell battery in key fob (key #5)
  • Poor battery contact or corroded battery holder in the key
  • Incorrect battery type or polarity installed
  • Intermittent connection inside key fob (loose components)
  • Damaged or degraded RF antenna/receiver in vehicle (amplifier/module)
  • Software/firmware anomaly or false low-battery reporting by KOS module

Symptoms

  • Dashboard/keyless system message or lamp indicating key battery low for key #5
  • Keyless entry/lock/unlock or remote functions intermittent or nonfunctional for that key
  • Vehicle may fail to detect that specific key when attempting push-button start
  • Longer range required to operate remote functions or need to position key close to vehicle
  • Possible inability to start the engine using that key until battery is replaced

What to check

  • Inspect vehicle message center for exact wording/which key number is affected
  • Visually inspect the key fob for damage, corrosion, or moisture ingress
  • Check key fob LED (if present) operation when pressing buttons
  • Measure key fob battery voltage with a multimeter while idle and while transmitting (if possible)
  • Try a known-good spare key to confirm issue is limited to key #5
  • Scan vehicle communication modules for related codes and freeze frame data

Signal parameters

  • Key fob battery open-circuit voltage (nominal coin-cell ~3.0 V; low threshold commonly ~2.2–2.6 V depending on system)
  • Transmitted RF burst amplitude / signal strength (relative dBm if available)
  • Wake/ID transmission pulse pattern (presence/absence)
  • KOS module received signal quality/error counts (if available via OEM scan tool)
  • CAN/LIN messages indicating key detection events and battery status flags

Diagnostic algorithm

  1. Confirm the DTC and note which key number is reported using an OEM-level scan tool. Check for additional related codes.
  2. Ask the owner about symptoms and whether the affected key has been replaced or exposed to moisture/impact.
  3. Attempt to reproduce the symptom: operate the key fob at various distances and try starting with that key.
  4. Inspect the key fob: open and check battery type, orientation, contacts, and any corrosion or loose parts.
  5. Measure the coin-cell battery voltage with a multimeter. If voltage is at or below system low threshold (typically ~2.2–2.6 V) or well below nominal, replace the battery.
  6. After battery replacement, verify the key fob LED and remote functions operate normally. Confirm vehicle recognizes the key and that the DTC clears (erase codes if needed) and does not return.
  7. If battery voltage is good but symptoms persist, try a known-good spare key. If spare works, suspect internal key fault; replace key fob or repair contacts.
  8. If multiple keys report low battery or intermittent detection, inspect vehicle KOS antenna/amplifier and related wiring/connectors for damage; check ground and connector corrosion.
  9. Use OEM diagnostics to monitor received signal strength and battery-status messages from the KOS module. Update module software if a known software bug applies.
  10. If the key fob is damaged or cannot be repaired, replace/reprogram the key per manufacturer procedure. Retest and clear codes. If problem persists after replacing keys and antenna hardware, further module-level diagnosis or replacement may be required.

Likely causes

  • Normal battery end-of-life in the key fob (most common)
  • Battery not seated or contacting properly after previous replacement
  • User replaced battery with wrong size or lower-capacity type
  • Key fob internals damaged by impact or moisture causing high internal resistance
  • Vehicle antenna/receiver marginal, causing module to interpret weak signal as low battery

Fault status

⚠️ Status
Low battery detected in Keyless/KOS key #5. Replace the key fob battery and verify key detection and remote function operation. If issue persists after battery replacement, inspect key and vehicle KOS hardware.
🟢 Repair difficulty: Easy
⏱️ Diagnostic time: 0.3-1.0 hours

Similar codes

B1A10 B1A11 B1A12 B1A13 B1A15
406

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