OBD-II trouble code
U0431: Invalid Data Received From Body Control Module 'A'
A module is receiving messages from body control module 'A', but the data inside them is implausible or out of range. The link is alive — the content is wrong. Can affect a wide range of body electrical features.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,100
- DIY difficulty
- Shop recommended
What does U0431 mean?
The body control module (BCM) is one of the busiest controllers in the car. It manages and relays a large share of the body electrical systems — exterior and interior lighting, wipers, power windows and locks, keyless entry, warning chimes, and often the gateway of information between comfort features and the powertrain and chassis networks. Body control module 'A' broadcasts the status of these systems to the rest of the network. U0431 sets when a receiving module is still hearing from body control module 'A', but the data in its messages is invalid: a value is out of range, implausible, or contradicts what other modules see. The link is alive; the content can't be trusted. That is the key difference from a lost-communication code, which means the module has gone completely silent.
Because the fault is bad data rather than a dead bus, the causes cluster around whatever makes the module broadcast wrong information. Because the BCM touches so many inputs, a single failing switch, sensor, or body actuator can push it into reporting an implausible value. Low system voltage is one of the most common triggers of all — the BCM is very sensitive to voltage, and a weak battery or poor ground frequently produces intermittent invalid-data codes here. The module's own software can be at fault if it is outdated, corrupted, or was never properly programmed after a replacement, and corroded connectors, water intrusion, or chafed wiring — the BCM often lives low in the dash or kick panel where moisture can reach it — can corrupt otherwise-good messages in transit.
Symptoms are as broad as the systems the BCM controls. You may see a check engine light plus odd body-electrical behavior: lights, wipers, locks, windows, or chimes acting erratically, warning messages, features that intermittently stop working, or occasionally issues with keyless entry and start on vehicles where the BCM participates in that. The car usually stays driveable because core engine, brake, and steering control don't depend on the BCM, but the affected convenience and safety-lighting features can be unreliable, so it's worth diagnosing. Because U0431 is frequently a secondary code, read the full list — a companion body, voltage, or component code often names the real root cause, and low voltage is worth ruling out first.
Common causes
- Low system voltage, a weak battery, or a poor ground — a very common BCM trigger
- Failing switch, sensor, or body actuator feeding the BCM an implausible value
- Water intrusion or corrosion at the BCM connectors or in its location low in the dash/kick panel
- Corroded connectors or chafed wiring corrupting messages in transit
- Outdated, corrupted, or mismatched body control module software
- Body control module 'A' replaced without proper programming
- Electrical noise or damaged bus wiring corrupting messages
- Body control module internal fault
Symptoms
- Check engine light with assorted body-electrical warnings
- Erratic exterior/interior lighting, wipers, power windows, or door locks
- Warning chimes or dash messages that come and go
- Convenience features intermittently dropping out
- Occasional keyless-entry or start issues where the BCM participates
- Companion body, voltage, or component codes stored alongside U0431
Diagnostic steps
- 1.Read ALL stored codes first — U0431 is often secondary to a body, voltage, or component code that names the real fault.
- 2.Load-test the battery and check charging voltage and grounds; low voltage is a leading BCM cause.
- 3.Inspect the BCM connectors and its area for water intrusion, corrosion, and loose pins.
- 4.Use live data to compare the BCM's reported inputs against actual switch/sensor states.
- 5.Trace any companion component code to the specific switch, sensor, or actuator involved.
- 6.Check bus wiring near the BCM for chafing and damage.
- 7.Verify the module has the correct, current calibration, then address companion codes before condemning the module.
Repair cost
$100 – $1,100
Cost depends on what is producing the bad data. Correcting low voltage, a weak battery, or a bad ground is often $150-$400. Repairing a corroded connector or water intrusion varies with access. A failing switch, sensor, or body actuator is typically $100-$400 installed. A module reflash is $100-$300, and body control module replacement with programming is the expensive case at $400-$1,100 — but that should only follow thorough diagnosis, since U0431 is frequently a secondary code and low voltage is a common, cheap fix.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.