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DTC codes / U04xx · Invalid data received from a module / U0424

U0424Invalid Data Received From HVAC Control Module

U0424 is a communication fault indicating that a control module, typically the engine or body control module, received invalid or implausible data from the heating, ventilation, and air conditioning (HVAC) control module over the controller area network (CAN) bus. The computer detected that the HVAC module's data messages were missing, corrupted, or outside expected parameters, so it flagged the signal as invalid rather than trusting it.

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

Symptoms you may notice

  • The check engine light or service vehicle soon light illuminates on the dashboard.
  • The HVAC system may default to a fixed temperature or blower speed, or stop responding to adjustments.
  • The climate control panel may be completely inoperative, with no display or button response.
  • In some vehicles, the engine cooling fan may run continuously or not at all because the powertrain control module loses HVAC request data.
  • Often no symptoms besides the warning light, especially if the HVAC module continues to broadcast valid data intermittently.
  • Other unrelated warning lights may appear if the CAN bus is disrupted and multiple modules lose communication.

Common causes, most likely first

  1. A failing or internally faulty HVAC control module that broadcasts corrupted or out-of-range data.
  2. Damaged, chafed, or corroded wiring in the CAN bus circuit between the HVAC module and other controllers.
  3. Loose or corroded electrical connectors at the HVAC control module or at a CAN bus splice point.
  4. Low battery voltage or a weak charging system causing the HVAC module to reset or transmit invalid data.
  5. A software or calibration issue in the HVAC module that requires a reflash or update.
  6. A shorted or open CAN bus line caused by water intrusion into the HVAC module or harness.
  7. Another module on the same CAN segment interfering with communication, though this is less common.

How to diagnose and fix it

  1. Perform a full scan of all modules to confirm U0424 is current and check for related communication codes that pinpoint the affected bus.
  2. Inspect the battery voltage and charging system, as low voltage is a frequent cause of spurious communication faults.
  3. Visually inspect the HVAC control module connectors and the CAN bus wiring for corrosion, chafing, or loose pins.
  4. Measure CAN bus resistance and voltage at the diagnostic link connector to verify bus integrity and rule out a short or open circuit.
  5. If wiring and power are good, substitute a known-good HVAC control module or perform a module swap test to see if the code clears.
  6. Check for technical service bulletins or software updates for the HVAC module that address invalid data transmission.
  7. After any repair, clear the code and verify that it does not return during a road test with the HVAC system operating through all modes.

Why the HVAC module sends invalid data

  • A common oversight is replacing the HVAC module when the real fault is a weak battery or poor ground that causes the module to boot up incorrectly and transmit garbage data.
  • U0424 can be set by a completely different module on the same CAN bus that is disrupting communication, so always check for other U-codes before condemning the HVAC module.
  • Some vehicles set U0424 when the HVAC module is disconnected during service and the code is stored historically; clearing it may be all that is needed if the system works normally.
  • Water intrusion into the passenger compartment or cowl area often corrodes HVAC module connectors and causes intermittent invalid data that only appears in damp weather.
  • The code does not always mean the HVAC module is bad; a faulty ignition switch or power relay that momentarily cuts power to the module can produce the same invalid data flag.

Can I keep driving with U0424?

You can usually continue driving safely because the fault mainly affects climate control, but avoid long trips in extreme temperatures where a non-functioning HVAC system could compromise comfort or defroster performance. If the engine cooling fan also stops working, monitor engine temperature closely and seek repair promptly.

Tools that help

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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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