B1864

Code

LAND ROVER B — Body

Battery power supply - module control circuit failure do motor

Brand: LAND ROVER

Type: B — Body

Views: UK: 12 EN: 29 RU: 17

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Causes

Low or intermittent vehicle battery voltage
Blown fuse or faulty relay in the supply circuit
Corroded, loose or damaged battery/motor/module connectors
Broken or shorted wiring between battery, module and motor
Faulty control module (internal supply/regulation failure)
Motor with excessive current draw (mechanical seizure or shorted windings)

Symptoms

Affected motor does not operate (e.g., door lock/unlock failure)
Intermittent operation of motor or slow/weak movement
No audible motor noise when command is given
Related vehicle messages or warning lights displayed
Possible parasitic battery drain or battery voltage warnings

What to check

Confirm DTC B1864 with a compatible diagnostic scanner and note freeze-frame data
Check battery state-of-charge and charging system voltage (resting ~12.4–12.7 V; running ~13.5–14.8 V)
Inspect and test fuses and relays for the motor and module power supply
Visually inspect connectors and wiring at the battery, module and motor for corrosion, damage or loose pins
Measure supply voltage at the module power pin and at the motor connector while operating the circuit
Check ground continuity from module and motor to chassis/battery negative

Signal parameters

Module supply voltage: should be close to battery voltage when key on (typical idle 11–14.8 V)
Ground path resistance: low (near 0 Ω); high resistance indicates poor ground
Motor supply voltage when commanded: near battery voltage (voltage drop >1–2 V suggests wiring/connector issue)
Motor current draw: manufacturer-specific; typical small door motors often draw a few amps running and higher when stalled (commonly 2–10 A); significantly higher indicates seizure/short
Communication: module should be present on vehicle network (CAN) when scanned; loss of network messages may accompany supply faults

Diagnostic algorithm

Retrieve and record the DTC and any freeze-frame/related codes. Note when code is active vs. historic.
Verify battery charge and charging system. Recharge or replace battery if low and retest.
Visually inspect fuses, relays and wiring related to the affected module and motor. Replace any blown fuses and reseat relays/connectors.
With the ignition on, measure voltage at the module power pin and at the motor supply pin. Operate the motor command and observe voltage drop and presence/absence of PWM or switched supply.
Check ground continuity from module and motor to battery negative. Clean and tighten grounds as necessary.
If supply present but motor does not run, measure motor current during operation. If current is excessive, remove and bench-test the motor or replace it.
If wiring and motor check good, perform targeted backprobing of module inputs/outputs using wiring diagrams. Repair any damaged wiring or connectors.
If wiring and motor are good but fault persists, consider module replacement or reflash after confirming manufacturer technical bulletins. Clear codes and perform function test.
After repairs, clear codes, perform system tests and confirm DTC does not return and functionality is restored.

Likely causes

Corroded terminal or connector at the module or motor causing voltage drop
Blown fuse supplying the module or motor circuit
Damaged wiring harness in door area (pinched or chafed)
Failed door motor drawing excessive current and tripping module sensing
Module power regulator failure

Fault status

⚠️ Status

Module detected abnormal battery supply or control-circuit fault to the motor. The module has stored B1864 indicating the module’s power input, internal regulator or control output is outside expected parameters or the motor/heavy-load circuit is drawing excessive current.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

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B1864 — Battery power supply - module control circuit failure do motor