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Home / DTC / B2974 — Trunklid cylinder open:open line

B2974 — Trunklid cylinder open:open line

Detailed page for trouble code B2974.

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Code

B2974

MITSUBISHI B — Body

Trunklid cylinder open:open line

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

Causes

  • Broken or chafed wire in trunk harness (common at hinge area)
  • Disconnected or corroded connector at trunk lid cylinder or body harness
  • Failed trunk lid cylinder actuator/lock motor or position sensor
  • Blown fuse or open circuit in power feed to the trunk cylinder
  • Poor or missing ground connection
  • Water intrusion / corrosion in trunk connector or actuator

Symptoms

  • Trunk will not lock or unlock using key/remote
  • Trunk ajar, lock, or warning lamp/message displayed on dash
  • No actuation noise when operating trunk lock
  • Intermittent operation or only works with force or manipulation
  • Stored B2974 DTC and possibly related body system faults

What to check

  • Verify DTC with a scan tool and record freeze frame/live data
  • Visually inspect trunk lid cylinder connector and wiring harness, especially at hinge/pivot points
  • Check fuses and fusible links related to body/trunk circuits
  • Operate trunk lock while listening for actuator movement
  • Wiggle harness at hinge while operating to reproduce fault
  • Inspect for water damage, corrosion, or bent/broken pins at connectors

Signal parameters

  • Resting voltage at trunk cylinder power feed: ~0–0.5V (if module is commanding off) or battery voltage when commanded (approx. 11–14V)
  • Activation signal: battery voltage (~11–14V) should appear at cylinder power terminal when lock/unlock requested
  • Ground: continuity to chassis ground from cylinder ground terminal
  • Actuator coil resistance (typical solenoid/lock motor): commonly low ohms to tens of ohms; an open (OL) indicates open circuit
  • Scan tool live data: trunk cylinder status (open/closed) or lock command state should change when operating controls

Diagnostic algorithm

  1. Connect an OEM-compatible scan tool, confirm B2974 is present and note freeze frame/live data when fault set.
  2. Perform a visual inspection: check trunk cylinder connector, harness through hinge area, and body-side connector for damage, corrosion, or disengagement.
  3. With ignition ON (or according to service manual), backprobe the trunk cylinder connector. Have an assistant operate lock/unlock while you observe: verify presence of ~12V supply when commanded and good ground continuity.
  4. If no voltage present when commanded, trace back to the next connector/fuse/relay to find an open; check related fuse(s) and body control module output.
  5. If voltage is present at the harness but not at the actuator or resistance is infinite at the actuator, disconnect the cylinder and measure its coil/motor resistance. If open, replace the trunk cylinder/actuator.
  6. Perform continuity check between the trunk cylinder connector and the BCM/ground point to locate broken wiring (pay attention to areas that flex at the hinge). Repair any open or chafed wires, repair or replace corroded connectors.
  7. If actuator tests OK when bench-powered and wiring is confirmed good, check BCM outputs and module connectors; consult wiring diagram and test BCM driver circuit. Replace BCM only after confirming upstream wiring and connectors are good.
  8. Clear codes and re-test operation through several cycles and road/start cycles to ensure fault does not return.

Likely causes

  • Worn/chafed harness at trunk hinge (wire break)
  • Corroded connector pins at trunk lid cylinder
  • Defective trunk cylinder actuator (open coil or broken internal wiring)
  • Open fuse or fusible link feeding the cylinder circuit

Fault status

⚠️ Status
Trunk lid cylinder circuit — OPEN detected. Inspect trunk cylinder, connectors, wiring (hinge area), fuses and BCM connections.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-1.5 hours

Similar codes

B2975 B2799 B2781 B2810 U0121 U1000
406

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