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Home / DTC / B2971 — Trunklid cylinder open:SHT-BAT

B2971 — Trunklid cylinder open:SHT-BAT

Detailed page for trouble code B2971.

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Code

B2971

MITSUBISHI B — Body

Trunklid cylinder open:SHT-BAT

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

Causes

  • Short to battery on trunk lid cylinder/open switch circuit (damaged insulation, pinched wiring)
  • Faulty trunk cylinder or integrated switch (internal short)
  • Corroded or loose connector at trunk cylinder or body harness
  • Water ingress in trunk lid wiring or switch
  • Blown fuse or poor ground affecting circuitry (can produce erratic voltage)
  • Body control module (BCM) internal fault or incorrect input from sensor (less common)

Symptoms

  • Trunk open/ajar warning lamp illuminated or persistent trunk-open message
  • Trunk may not lock/unlock reliably from switch or remote
  • Interior dome/host module may show false trunk-open state
  • Possible parasitic battery drain if short is constant
  • Intermittent operation or changes with door/trunk movement

What to check

  • Retrieve freeze-frame data and stored codes with scan tool; note conditions when code set
  • Visually inspect trunk lid hinge area, wiring harness, and trunk cylinder connector for damage, chafing, corrosion or water entry
  • Check related fuses and fusible links for open/short conditions
  • With ignition off, disconnect trunk cylinder connector and recheck code status (see diagnostic steps)
  • Perform wiggle test of harness while watching scan tool for changes
  • Measure voltage at trunk cylinder connector with harness connected and with connector disconnected (follow diagnostic steps below)

Signal parameters

  • Typical: battery voltage ~12 V present on circuit when ‘short to battery’ fault is active (exact normal state depends on manufacturer design)
  • Expected switch states (example): closed = near 0 V or ground reference; open = battery voltage (~12 V) — confirm with service manual for exact logic
  • Continuity: closed switch should show low resistance (
  • No continuity between sensor circuit and battery positive with ignition off (check for unintended short)

Diagnostic algorithm

  1. Connect a diagnostic scanner, read and record B2971 and any related codes and freeze-frame data. Clear codes and attempt to reproduce.
  2. Visually inspect trunk lid harness, rubber boot at hinge, and connector at trunk cylinder for abrasion, cuts, corrosion, or water. Repair any obvious damage.
  3. With ignition off, disconnect trunk cylinder connector. Clear the code, then check if code returns with connector disconnected. If code does not reappear, suspect the trunk cylinder/switch assembly.
  4. With connector disconnected and ignition ON (or as required by vehicle), measure continuity between the trunk cylinder signal wire and battery positive. Continuity indicates a short to battery in the harness or connected component.
  5. With ignition ON, measure voltage at the signal wire at the connector while operating the trunk switch/cylinder. Compare to expected values from signal_params. Note any constant battery voltage when the circuit should be low/grounded.
  6. If wiring appears intact but measurements indicate internal short, remove and bench-test or replace the trunk cylinder/switch assembly. Re-test after replacement.
  7. If replacement does not clear the fault, trace the harness back toward the BCM, inspecting splice points and connectors. Repair or replace damaged wiring as needed.
  8. If wiring and actuator are good, check BCM inputs and grounds. Repair connector issues or replace/repair BCM only after confirming upstream wiring and sensor are correct.
  9. Clear codes, verify proper operation of trunk open/close indicators and remote locking, and road-test to ensure code does not return.

Likely causes

  • Damaged wiring harness in trunk hinge area causing bare conductor contact with +12V
  • Faulty trunk cylinder switch with internal short to battery
  • Corroded/contaminated connector at trunk cylinder

Fault status

⚠️ Status
Trunk lid cylinder open circuit — short to battery detected (SHT-BAT). Inspect trunk cylinder/switch and wiring for short to +12V.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B2970 B2972 B2797 B2785
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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