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Home / DTC / B101D — Switch of descent

B101D — Switch of descent

Detailed page for trouble code B101D.

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Code

B101D

LAND ROVER B — Body

Switch of descent

Brand: LAND ROVER
Type: B — Body
Views: UK: 5 EN: 12 RU: 6
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Page language: EN

Causes

  • Faulty descent (Hill Descent Control) switch
  • Damaged wiring or poor connector pins at the switch
  • Corroded or bent switch contacts
  • Blown fuse or power/ground loss to the switch circuit
  • Faulty body/Central Electronic Module (CEM) or ABS/ESC module that reads the switch
  • Software or CAN bus communication error between modules

Symptoms

  • HDC (Hill Descent Control) switch does not enable or disable descent control
  • HDC indicator or warning lamp on instrument cluster
  • Switch illumination not working or switch stuck physically
  • Intermittent or no response when pressing the descent switch
  • Related stability/ABS/HDC functions may be unavailable

What to check

  • Use a diagnostic scan tool to read B101D and any associated codes and to view live data/state of the descent switch
  • Check for stored freeze-frame, event counts, and whether the fault is current or historic
  • Visually inspect the descent switch and surrounding trim for damage, contamination or water ingress
  • Inspect the switch connector for corrosion, bent pins, or poor contact; wiggle test while watching live data for change
  • Check fuses and power/ground at the switch circuit
  • Inspect harness routing for chafing, pinched sections or previous repairs

Signal parameters

  • Switch type: momentary or toggle input reported as a digital signal to CEM/ABS (refer to vehicle wiring diagram)
  • Typical expected: inactive = logic/high (approx. 4–5V on reference circuits) and active = logic/low or ground (approx. 0–0.5V) — verify exact values against wiring diagram
  • Closed-circuit continuity when switch pressed: near 0 Ω through contact (when applicable)
  • CAN message: module should report switch state; absence of message or constant value indicates fault

Diagnostic algorithm

  1. Connect a dealer-level or capable scan tool. Read and record B101D and any other codes. Note whether code is active or intermittent.
  2. Attempt to activate the descent function while watching live data for the switch state. Confirm whether the module sees a state change when pressing the switch.
  3. Visually inspect switch assembly, trim, and connector. Remove switch and check terminals for corrosion, bent pins, or water damage.
  4. With ignition on, back-probe the switch connector and measure reference voltage and switch output while pressing the switch. Compare to wiring diagram reference values.
  5. Check continuity to ground or between switch pins when operated (bench test the switch if removed). Replace switch if contacts do not change state correctly.
  6. If switch electrical behaviour is correct, inspect harness continuity to the controlling module and check for short to power or ground. Repair wiring as necessary.
  7. Check fuses, module power and ground. If wiring and switch OK, check for communication errors on CAN bus and for related module faults (CEM or ABS/ESC).
  8. If modules and wiring are correct but the code persists, consider module firmware/software update or replacement per manufacturer guidance. After repairs, clear codes and perform function test and road test to confirm.
  9. Document findings and recheck after test drive; if intermittent, monitor for recurrence and inspect for environmental causes (moisture).

Likely causes

  • Switch contacts worn or stuck from dirt/moisture
  • Broken/frayed harness or chafed insulation near the switch or steering column
  • Loose or corroded connector at switch or CEM/ABS module
  • Intermittent ground or supply to the switch
  • Failed switch after water ingress or impact

Fault status

⚠️ Status
Descent (Hill Descent Control) switch circuit fault — switch not detected or reporting invalid signal. HDC may be unavailable.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B101C B101E B1001 B10A0 B10B2 B10C0
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