OBD-II trouble code
U0426: Invalid Data Received from Immobilizer / Vehicle Security Control Module
A module is receiving messages from the immobilizer / vehicle security control module, but the data is implausible, out of range, or fails authentication. The connection is alive — the content is wrong. Often a key, calibration, or programming fault, or a network issue corrupting it.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $100 – $1,100
- DIY difficulty
- Shop recommended
What does U0426 mean?
U0426 is different from a 'lost communication' code. Here the receiving module is still hearing from the immobilizer / vehicle security control module — the connection is alive — but the data inside those messages is invalid: a value is out of its expected range, implausible, missing, or fails the security authentication the engine computer expects. The messenger is talking, but what it's saying doesn't make sense or doesn't authenticate, so the receiving module rejects the data and stores U0426.
The immobilizer system exists to stop the engine from starting unless a valid, programmed key is present. The security module reads the key's transponder, validates it, and passes an authorization message to the engine computer over the network. Because the problem with U0426 is the content of that data rather than the link itself, the causes lean toward whatever makes the security module send bad or unauthenticated information. A key that isn't properly programmed, a failing key transponder or antenna ring around the ignition, a security module with incorrect or corrupted programming after replacement, or a mismatch between modules that were not married to each other can all produce invalid data. The security module itself can have an internal fault. Network problems can still play a role: electrical noise, a marginal bus, wiring issues, or low system voltage can corrupt otherwise-good messages.
The practical effect is often a no-start or a stall shortly after starting, because the engine computer will not allow the engine to run if it can't get a valid security authorization. You may also see a security or immobilizer warning light, a flashing key/lock icon, or anti-theft messages in the cluster. Because U0426 can prevent the vehicle from starting and the underlying cause frequently involves key programming or module marrying that requires the correct equipment, it should be diagnosed by reading the full code set and confirming the key, the security module programming, and the network before replacing parts.
Common causes
- Key not properly programmed, or a worn/failing key transponder
- Faulty immobilizer antenna ring around the ignition lock
- Security module with incorrect, corrupted, or mismatched programming
- Modules not 'married' (synchronized) after a replacement
- Immobilizer / vehicle security control module internal fault
- Low system voltage causing implausible or failed authentication data
- Electrical noise, a marginal bus, or wiring corrupting messages
- Aftermarket alarm or remote-start interfering with the security network
Symptoms
- Engine cranks but will not start, or starts then stalls
- Security / immobilizer warning light or flashing key/lock icon
- Anti-theft message in the instrument cluster
- Intermittent no-start that comes and goes
- Remote start or keyless features failing
- Multiple related security or communication codes stored alongside U0426
- Often not driveable until the authorization fault is resolved
Diagnostic steps
- 1.Read ALL stored codes first — U0426 is often accompanied by security or immobilizer codes that name the specific fault.
- 2.Check system voltage and the battery/charging system; low voltage can cause failed authentication and false security faults.
- 3.Confirm the key is correctly programmed and the transponder reads; try a known-good spare key if available.
- 4.Inspect the immobilizer antenna ring and ignition-area wiring and connectors for damage.
- 5.Verify the security module and any recently replaced modules have the correct programming and are properly married to the vehicle.
- 6.Inspect bus wiring and check for aftermarket alarm or remote-start systems tapped into the security network before replacing the module.
Repair cost
$100 – $1,100
Cost depends entirely on what's producing the bad data. Key programming or cutting a new programmed key is often $80-$300. An immobilizer antenna ring is typically $100-$350 with diagnosis. Correcting low voltage or a charging fault runs $150-$600. Security module programming or marrying modules is typically $100-$300 with the correct equipment. Security/immobilizer module replacement and programming is the expensive case at $500-$1,100+ and should only follow thorough diagnosis. Some of this work requires dealer-level tools and security access.
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.