B2390 — Master-Slave Body Communication Failure

B2390 — Master-Slave Body Communication Failure. B2390 indicates a failed body-module communication link, so one or more controlled features may be unavailable.

For Ford vehicles

master / slave communication – failure

vehicle

Is it safe to drive?

Diagnose promptly B2390 indicates a failed body-module communication link, so one or more controlled features may be unavailable. Arrange diagnosis promptly and do not rely on an affected function until it operates normally.

Typical symptoms

B2390 appears as a current, pending, or historical scan code
The affected slave module does not answer requests from the body master module
One or more body features controlled by the slave module fail to operate
Intermittent resets or feature dropouts occur when a connector or ground is disturbed
B2390 can remain stored after the communication fault has temporarily recovered

Common causes

Failed body slave module or damaged internal communication circuitry
Damaged wiring harness, connector, or terminal between the master and slave modules
Loss of battery power, fuse protection, or ground at the slave module
Open, shorted, or high-resistance wiring on the applicable communication bus
Faulty body master control module
Incorrectly programmed, incompatible, or corrupted slave-module software

How to diagnose with an OBD scanner

Confirm B2390 with a scanner Connect an ELM327 adapter, AIScanAuto, or equivalent scanner and read all accessible body-control modules. Record whether B2390 is current, pending, or historical, and save freeze-frame data before disconnecting power.
Identify the affected module pair Use vehicle service information and enhanced scanner data to identify which body master and slave modules participate in the B2390 communication circuit. Do not replace a module based on the code alone because the source definition does not name the slave module.
Inspect power, ground, and connectors Check battery voltage, applicable fuses, ground points, connector terminals, and the wiring between the identified master and slave modules. Perform voltage-drop and continuity tests according to the applicable circuit diagram.
Test the communication circuit Use the specified communication-bus procedure to verify that the master module sends commands and the slave module returns valid responses. Inspect bus wiring and terminations if the service information identifies a terminated network.
Verify module operation and programming If power, ground, and wiring pass, perform the manufacturer-specified communication test. Verify module part compatibility, software status, and programming before considering master or slave module replacement.
Clear and validate B2390 Clear the code with the scanner after repair, cycle the ignition as directed, and operate the affected body functions. Confirm that B2390 does not return and that the master and slave modules exchange data normally.

Approximate repair cost

An independent shop may charge roughly USD $125-$500 for B2390 diagnosis and repair, with the final cost depending on whether the fault requires wiring repair, connector service, programming, or module replacement. These figures are estimates only, not verified quotes; parts, labor rates, and programming charges vary by region.

Common questions

What does code B2390 mean?

B2390 means the body master module could not establish valid communication with the designated slave module.

Can the vehicle still be driven with B2390?

A current B2390 normally warrants prompt diagnosis because affected body features may not respond. Repair should be completed before relying on those functions.

What is the most common cause of B2390?

Common B2390 causes include damaged wiring, a poor connector, inadequate module power or ground, failed slave-module electronics, or incorrect module programming.

Can an ELM327 scanner locate the B2390 fault?

An ELM327-compatible scanner can confirm B2390, show its status, and capture related data, but vehicle service information and circuit testing are still needed to identify the failed link.

B2390 — B2390 — Manufacturer Controlled DTC: Causes, Symptoms & Fix

When a scan tool pulls code B2390, it's flagging a fault within the body's electrical infrastructure — the network of components that manage windows, door locks, interior and exterior lighting, wipers and related accessories. This code belongs to the B-series family, which handles body-related problems rather than engine or transmission issues. The ECU or body control module logs B2390 once it detects that a component or circuit within this system has strayed outside its intended operating parameters.

The logic behind B2390 involves continuous monitoring. The relevant control module samples sensor values and actuator states, then compares them against factory-defined thresholds. When readings fall outside acceptable ranges for a set period — often across multiple drive cycles — the module flags the fault and saves a freeze frame. This snapshot captures rpm, engine load, coolant temperature and vehicle speed the instant the problem occurred. Reviewing that data first points you toward the right circuit before touching a single wire.

Symptoms of B2390

The engine and transmission behave normally in most cases — B2390 does not directly affect drivability
The malfunctioning component operates erratically, partially or not at all (door locks, windows, lighting or wipers)
A dashboard warning light may illuminate depending on the vehicle
The affected function may work intermittently, making the fault harder to pin down
In some vehicles the issue only appears under specific conditions such as temperature extremes or high humidity
No other drivetrain symptoms are expected with this code

Common causes of B2390

A faulty switch, motor or actuator within the affected body system is the most frequent culprit
Body control module (BCM) internal failure or software corruption
Corrosion, moisture intrusion or bent pins at electrical connectors
Broken or chafed wiring at flex points — door jambs, tailgate hinges and similar areas that flex with every open and close
A blown fuse or failed relay feeding the circuit
Loose grounds causing erratic module behavior
Aftermarket accessories installed incorrectly, drawing excessive current through the circuit

How to diagnose B2390

Plug in an OBD2 scanner, retrieve B2390 and record the freeze frame data. That snapshot tells you engine speed, load, coolant temperature and vehicle speed when the fault set — use it to recreate the failure conditions during testing.
Check for any related codes alongside B2390. Co-existing codes often point directly to the failing component. Also search manufacturer technical service bulletins for your specific make and model — many B0xxx codes have documented software updates or factory-recommended repair procedures. Search by VIN on the manufacturer site or NHTSA.gov.
Perform a thorough visual inspection of the wiring harness and connectors tied to the malfunctioning system. Look for corrosion, broken strands, melted insulation, rubbing against metal edges and any sign of water intrusion.
Use the scanner to monitor switch and motor PID values in live data while operating the affected function. The data should move in a predictable pattern; stuttering or flatlined values indicate a hardware problem.
Pay close attention to flex points. Wires inside door jambs and around tailgate hinges bend every time the door opens, making them the most common location for broken conductors. Wiggle the harness while watching live data for dropped signals.
Clear B2390, complete a full drive cycle that reproduces the freeze-frame conditions, then re-scan. If the code returns, the underlying fault is still present and requires physical repair or replacement.

Repair options and costs for B2390

Address the least expensive and most common failures before committing to a full module replacement:

BCM repair by a specialist or full replacement with programming: $300–$900 (parts and labor, independent shop rates)
Wiring harness repair, connector replacement or terminal renewal: $80–$250
Switch or actuator replacement for the affected component: $120–$450

Total cost to fix B2390

Your final bill depends entirely on which part failed. Based on typical independent shop labor rates in the United States:

BCM repair or replacement: $300–$900
Wiring or connector work: $80–$250
Switch or actuator replacement: $120–$450

Across all scenarios, fixing B2390 generally runs between $80 and $900. An accurate diagnosis before purchasing parts pays for itself — the BCM is rarely the first thing to check, yet it is often the most expensive fix on the list.

Can you drive with B2390?

In most cases, yes. Body codes like B2390 typically do not impair engine operation or transmission function, so the vehicle remains drivable. Exercise extra caution when exterior lighting or wipers are affected, and address central locking failures promptly — a door that will not lock properly leaves your vehicle unsecured. Treat these as priority repairs rather than cosmetic inconveniences.