U0426: Invalid Data Received From Vehicle Immobiliser Control Module
What to do
If the car cranks but will not start, look for a security or key symbol on the dashboard. That symbol is the difference between a fuel problem and a security problem, and it sends the diagnosis in completely different directions.
Three free things to try before calling anyone, and between them they solve a great many of these:
- Try your spare key. If the car starts on it, the vehicle is fine and the first key is the problem.
- Take the key off the keyring. A second key, a metallic fob or a phone or contactless card held against it can stop the car reading the transponder.
- Consider the battery. A tired battery drops voltage while cranking and makes the security check fail, even though everything looks normal. This is common and cheap.
If it is a genuine module fault, it needs a dealer or an auto-locksmith — these modules have to be paired to your car and your keys, and a second-hand one from another vehicle will never work no matter who fits it.
What this code means
The immobiliser module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing.
An immobiliser exists to stop the engine running for anybody without the right key, and its design principle is that ambiguity must fail closed. A security system that started the engine when it was unsure would not be a security system. So an implausible immobiliser report produces a vehicle that will not start, and that is the system working as intended rather than failing.
The presentation is distinctive and worth recognising, because it sends people to the wrong place. Everything electrical works normally, the engine turns over, and it will not fire — or it fires for a second and stops. A driver seeing that reasonably suspects fuel or ignition, and the actual cause is a handshake that could not complete. The security or key symbol on the dashboard is the clue, and it is worth looking for before anything else.
Before assuming a fault, three innocent explanations account for a great many of these and cost nothing.
The key itself. A worn transponder, a damaged key, or simply the wrong key from a set. Trying the spare key is the single most valuable test available, and if the car starts on it, the vehicle is fine.
Interference. A second key on the same ring, a metallic keyring, or a phone or contactless card held against the key can prevent the transponder being read. Separating the key from everything else and trying again is free.
A weak battery. Low voltage during cranking makes the security exchange fail while everything looks normal. This is common, cheap and regularly missed.
And where a genuine fault exists, the corpus's standing point about immobiliser work applies: replacement modules must be paired to the vehicle and its keys, which is dealer or specialist work, and a second-hand module locked to another vehicle will never function.
Likely causes
Start here
- Faulty immobiliser control module · specialist
- Corroded or loose connector · easy
- Faulty aftermarket alarm or immobiliser installation · moderate
Less common
- Second hand module locked to another vehicle · specialist
- Module not coded to the vehicle · specialist
- Damaged data bus wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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