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Home / DTC / B129E — Activation/deactivation key - Advanced semi-automatic parallel park

B129E — Activation/deactivation key - Advanced semi-automatic parallel park

Detailed page for trouble code B129E.

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Code

B129E

LAND ROVER B — Body

Activation/deactivation key - Advanced semi-automatic parallel park

Brand: LAND ROVER
Type: B — Body
Views: UK: 7 EN: 13 RU: 8
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Page language: EN

Causes

  • Faulty activation/deactivation switch or steering‑column button
  • Damaged wiring or connectors between switch and Body Control Module (BCM)
  • Poor ground or low supply voltage to switch/BCM (battery/charging issues)
  • Intermittent or lost CAN/LIN communication between modules (BCM, parking control module, instrument cluster)
  • BCM or Parking Aid Control Module software/configuration or calibration fault
  • Corrosion, water ingress or mechanical damage in connectors or switch assembly

Symptoms

  • Push‑button or key to enable/disable parallel park does not respond
  • Instrument cluster or infotainment displays a message that Advanced Semi‑Automatic Parallel Park is disabled or unavailable
  • Related warning lamp or message referring to park assist or auto park
  • System cannot be engaged or will disable immediately after activation attempt
  • No change in system state when using switch, but other parking sensors may still work

What to check

  • Read and record all stored DTCs from BCM, Parking Aid Control Module and instrument cluster; note freeze frame data
  • Check battery voltage and charging system health (low voltage can cause module errors)
  • Inspect fuses and power/ground circuits related to BCM and parking aid module
  • Visually inspect switch, steering column trim, and connector for damage, corrosion or water ingress
  • Operate the activation/deactivation switch while monitoring input state with a diagnostic tool or digital multimeter
  • Check for CAN/LIN bus communication errors and verify modules for bus presence using a scan tool

Signal parameters

  • Switch input state: closed/open when pressed (expected change on actuation)
  • Switch circuit voltage: reference ~0–12 V (or 0–5 V depending on design) with key on; check for expected pull‑up/pull‑down behavior
  • Ground continuity: low resistance from switch ground to chassis (
  • Module supply voltage: battery voltage present at BCM/parking module connectors (approx. 12 V with ignition on)
  • CAN bus: relevant message IDs for parking/BCM present and periodic (no timeouts); bus voltage nominal (~2.5 V differential idle)

Diagnostic algorithm

  1. Connect a full‑function scan tool and read/record all related DTCs from BCM, Parking Aid Control Module and instrument cluster; clear codes and attempt to re‑capture
  2. Verify battery voltage and condition; charge battery or reconnect if low and repeat test
  3. Inspect fuses and relays for the BCM/parking system and replace if blown
  4. Visually inspect the activation/deactivation switch, associated harness and connectors for damage, corrosion or loose pins; repair as needed
  5. With ignition on, backprobe the switch connector and verify reference voltage and switching signal when pressing the button; compare to expected values
  6. Check ground continuity from switch/connector to chassis/ground point
  7. Monitor CAN/LIN traffic with a diagnostic tool while pressing the switch to confirm the module transmits/receives the appropriate messages; note any timeouts or bus errors
  8. If wiring and switch test OK but no messages reach the parking module, trace wiring back to BCM and test continuity; repair any open/short circuits
  9. If communications are lost or module behaves erratically, check for recent software updates or module replacements and verify correct coding; perform module reprogramming or software update if recommended by manufacturer
  10. Replace switch or repair wiring if fault confirmed; if problem persists, consider BCM or Parking Aid Control Module fault and proceed with module bench tests or replacement per manufacturer procedures
  11. After repairs, clear codes, verify system enable/disable function and road/test to confirm no reoccurrence

Likely causes

  • Failed or sticky activation/deactivation switch on steering column or dash
  • Loose/damaged connector at switch or BCM causing intermittent open/short
  • CAN bus messages from the switch not present (module communication fault)
  • Incorrect module coding after replacement or software issue following recent updates

Fault status

⚠️ Status
Activation/deactivation input for Advanced Semi‑Automatic Parallel Park unavailable or outside expected range. Switch or communication fault; system may be disabled.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B129D B129F U0100 U0140 B129C
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