U0426: Invalid Data Received from Vehicle Immobiliser Control Module

What it means

The Vehicle Immobiliser Control Module is present on the data bus but the values it reports are implausible — out of range, frozen, or failing the checksum or rolling-count check. The receiving modules reject the data. Start authorisation may fail. Causes include a faulty sensor feeding the module, internal computation errors, a software or calibration mismatch after a repair, or bus interference corrupting the frames.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

The Vehicle Immobiliser Control Module handles or reports start authorisation using the vehicle's security system. U0426 sets when another module rejects the immobiliser's data as implausible, which can prevent starting but does not by itself prove that a key or immobiliser module has failed.

Common causes

Most likely first.

1. Immobiliser internal fault
2. CAN corruption causing checksum errors
3. Gateway module routing CAN messages incorrectly

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and record immobiliser, starting, and network codes along with freeze-frame data before clearing anything.
2. Check whether the vehicle starts consistently and whether a security or key warning appears; note any recent key, battery, or module work.
3. Inspect the immobiliser module connector and accessible network wiring for looseness, corrosion, or damage.
4. Check module power and ground circuits to the manufacturer's specification, and verify that the vehicle recognises the key using the available scan-tool data.
5. Test network communication and gateway routing using vehicle service information, and check for software or configuration mismatches after repairs.
6. Consider module repair or replacement only after key recognition, power, grounds, wiring, and network communication have been checked.

Common fixes

• Repair a loose or corroded immobiliser connector or network wire.
• Correct a power or ground fault at the immobiliser module.
• Resolve an applicable key recognition or module configuration issue using the manufacturer's procedure.
• Correct a gateway routing or software mismatch.
• Repair or replace the immobiliser module if its supply and network circuits test correctly but its data remains invalid.

Can I keep driving?

If the engine will not start or start authorisation is intermittent, avoid relying on the vehicle until the fault is diagnosed because it may leave you stranded. If it is running normally, do not switch it off in an unsafe location.