B1D78

Code

LAND ROVER B — Body

Auxiliary entrance

Brand: LAND ROVER

Type: B — Body

Views: UK: 10 EN: 14 RU: 13

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Page language: EN

Causes

Loss of communication with the auxiliary entrance module (CAN/LIN bus fault)
Blown fuse or removed/loose power supply to the auxiliary entrance module
Poor ground connection or corroded connector at the module or harness
Damaged wiring (open/short) to auxiliary door/entry sensors or module
Faulty auxiliary entrance module or associated door control unit
Water ingress or corrosion in connectors/sensors (sills, doors)

Symptoms

Instrument cluster message or warning related to auxiliary entry
Loss of auxiliary entrance functions (e.g., courtesy lights, entry sensors, remote entry features)
Intermittent operation of door/entry sensors or convenience functions
Stored or recurring fault code even after ignition cycles
Other body system errors or network-related warnings

What to check

Read all stored and pending codes from all modules with a suitable Land Rover diagnostic tool; note freeze frame and accompanying codes
Verify battery voltage is stable and within specification (engine off and cranking conditions)
Inspect fuses and relays related to body/entry/auxiliary circuits
Visually inspect connectors and wiring at the auxiliary entrance module, doors, and sills for corrosion, damage, or water ingress
Check ground connections for continuity and corrosion at body control module and nearby grounds
Check CAN/LIN bus status and verify communication to the affected module using a diagnostic tool

Signal parameters

Module supply voltage: battery voltage present at module power pin when ignition ON (nominal ~12 V)
Ground continuity: low-ohm connection from module ground to chassis ground
CAN/LIN communication: active messages present from other body modules; module should respond to diagnostic requests
Switch/sensor resistance: closed switch near 0 Ω, open switch high resistance (compare to specification)
Diagnostic responses: module should return a valid status and live data when communicating

Diagnostic algorithm

Connect a Land Rover-capable scanner, read B1D78 and any related codes from all modules. Record freeze frame and module reporting the fault.
Check battery condition and voltage. Low battery or unstable supply can cause communication faults—rectify if necessary and retest.
Inspect fuses and relays for the body/auxiliary circuits; replace any blown devices and verify presence of power at the module power terminal with ignition ON.
Visually inspect connectors, pins and wiring on the auxiliary entrance module, door harnesses, sill sensors and related joints. Look for corrosion, bent pins, water ingress, or repair splices.
Verify ground continuity from the module ground pin to chassis ground with a multimeter. Clean/tighten grounds as required.
Using diagnostic tool, check CAN/LIN bus health and module comms. If the module is not responding, trace communication wiring and test for continuity/shorts to battery or ground.
Test the entry sensors/switches (door, sill, or auxiliary switches) for proper resistance/operation. Replace or repair any sensor that fails electrical or functional tests.
If wiring, power and grounds are good but communication or function remains faulty, try module reset/clear codes and re-test. If persistent, check for software updates and apply official reflash/reprogram procedure.
If module hardware fault is confirmed by bench testing or non-responsiveness after all wiring and power checks, replace the auxiliary entrance/module per manufacturer procedure and program/configure it with the dealer tool.
After repair, clear stored codes, perform full system test, and verify the fault does not reoccur under normal conditions.

Likely causes

Intermittent or lost CAN/LIN communication to the auxiliary entrance module
Corroded/loose connector or poor ground at the module harness
Blown fuse or missing supply voltage to the module
Failed door/entry sensor or switch (open/short)
Module hardware failure or software fault after an update

Fault status

⚠️ Status

Auxiliary entrance: detected fault with auxiliary entrance module, its power/ground, sensors, or communication. Functionality may be reduced or unavailable.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.8-2.0 hours

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