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DTC codes / U04xx · Invalid data received from a module / U0426

U0426Invalid Data Received From Vehicle Immobilizer Control Module

U0426 means the engine computer or another module on the network received data from the vehicle immobilizer control module that it considers invalid or implausible. The immobilizer module is responsible for reading the key transponder and authorizing engine start, so the receiving module has detected a message that does not match expected values or fails its internal consistency check.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaInvalid data received from a module

Symptoms you may notice

  • The security or immobilizer warning light stays on or flashes after the key is turned
  • The engine cranks but will not start, or starts and stalls immediately
  • Intermittent no-start condition that may clear after several attempts or a battery disconnect
  • A stored U0426 code alongside other communication or immobilizer-related codes
  • Often no symptoms besides the warning light, with the vehicle starting and running normally

Common causes, most likely first

  1. A weak or failing key fob battery causing the transponder signal to be intermittent or corrupted
  2. Corroded, loose, or damaged wiring and connectors between the immobilizer module and the network bus
  3. A failing immobilizer control module that intermittently sends malformed or invalid data frames
  4. Low system voltage or a weak vehicle battery causing modules to drop off the network briefly
  5. A faulty ignition switch or key reader coil that interrupts the immobilizer handshake
  6. Aftermarket remote start or alarm systems wired into the immobilizer circuit and corrupting data
  7. A software or configuration mismatch in the immobilizer module after a replacement or reflash

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, and record freeze-frame data to see when U0426 set
  2. Test the vehicle battery and charging system, as low voltage is a common cause of invalid network data
  3. Replace the key fob battery and try a second known-good key to rule out a failing transponder
  4. Inspect and clean the immobilizer module connectors and the wiring harness for corrosion or chafing
  5. Check network bus voltage and resistance at the immobilizer module to confirm the communication line is healthy
  6. If wiring and power are good, perform a dealer-level reprogram or replacement of the immobilizer module and relearn the keys
  7. Clear codes and road-test, then recheck for returning U0426 and any companion codes

What the immobilizer data check really means

  • U0426 is a data-validity fault, not a no-communication fault, so the immobilizer module is still talking on the network but sending values the receiving module rejects.
  • A weak key fob battery is frequently overlooked because the vehicle may still start intermittently, yet the low transponder signal corrupts the data frame enough to set U0426.
  • Aftermarket remote starters and alarm systems spliced into the immobilizer wiring are a common hidden cause, especially when the code appeared after an accessory install.
  • The code can be set by a momentary voltage dip during cranking, so a battery that passes a basic load test may still be the root cause under cold-start conditions.
  • Replacing the immobilizer module without a proper key relearn will leave the vehicle in a no-start state and may set additional codes, so programming must follow replacement.

Can I keep driving with U0426?

The vehicle may start and drive normally, but because the immobilizer can refuse to authorize a start at any time, avoid trips where a no-start would leave you stranded. If the engine already fails to start, do not keep cranking and seek diagnosis before the battery is drained further.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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