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Home / DTC / B1406 — Auxiliary fuel heater

B1406 — Auxiliary fuel heater

Detailed page for trouble code B1406.

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Code

B1406

LAND ROVER B — Body

Auxiliary fuel heater

Brand: LAND ROVER
Type: B — Body
Views: UK: 3 EN: 8 RU: 12
AI status
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Page language: EN

Causes

  • Open or short in auxiliary fuel heater power or ground circuit
  • Blown fuse or faulty relay supplying the heater
  • Poor or corroded connector or terminal at the heater
  • Failed auxiliary fuel heater element
  • Control module (BCM/ECM) output fault or software issue

Symptoms

  • Longer cranking and harder cold starts on diesel models
  • Extended white smoke or rough idle until engine warms
  • Heater or glow system warning lamp/message
  • Reduced fuel system performance in cold conditions
  • Possible stored fault lamp (MIL) or body warning

What to check

  • Read stored and pending codes with a compatible scan tool; note freeze-frame/capture data
  • Inspect fuse(s) and relay(s) for the auxiliary fuel heater and replace as needed
  • Visually inspect wiring, connectors and pins for corrosion, damage or loose fit
  • Measure battery voltage at the heater power pin with ignition on
  • Check ground continuity from heater ground to chassis
  • Measure heater element resistance against manufacturer specification

Signal parameters

  • Supply voltage: battery voltage (~12 V) at heater power pin with ignition ON or when commanded
  • Control signal: switched ground or switched +12 V from body/control module (verify with wiring diagram)
  • Heater element resistance: low ohms range (check vehicle-specific service data for exact value)
  • Command duty/pulse: on/off or PWM when controlled by module (scan tool should show commanded state)
  • Current draw: measurable when heater is energized (compare to spec to detect open/high resistance)

Diagnostic algorithm

  1. Retrieve code(s) and related data with a scan tool. Record current conditions and any related body or engine codes.
  2. Inspect external components: check fuses, relays and visible wiring/connectors for the auxiliary fuel heater. Repair or replace obvious faults.
  3. With connector disconnected, measure heater element resistance to verify it is within the manufacturer specification. Replace heater if open or out of spec.
  4. Verify power supply: with ignition ON and/or heater commanded ON via diagnostic tool, measure battery voltage at the heater power terminal.
  5. Verify control/ground: command heater ON and measure the control circuit for switching (voltage change or ground switching). If module does not command, check input conditions and related sensors.
  6. If wiring/power and heater element check good, backprobing may be required to test for intermittent or parasitic faults. Wiggle harness to check for intermittent faults.
  7. If wiring and heater are good but no correct command is present, suspect control module fault or software; consult manufacturer service info for module tests or reprogramming.
  8. After repairs, clear codes, perform functional tests including cold start verification, and recheck for reoccurrence.

Likely causes

  • Blown fuse or defective heater relay
  • Damaged wiring harness to auxiliary heater (abrasion, chafing, rodent damage)
  • Corroded or loose connector at heater module
  • High-resistance or open heater element
  • Control module not commanding or stuck output

Fault status

⚠️ Status
Stored DTC B1406 — Auxiliary fuel heater circuit or performance fault detected. Check heater power, ground, wiring, connectors and heater element; module may have logged the fault when heater did not operate as expected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2 hours

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B1400 B1401 B1402 B1407 P0037 P0135
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