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DTC codes / U04xx · Invalid data received from a module / U041C

U041CInvalid Data Received From Rocker Arm Control Module A

U041C is a communication fault indicating that a control module received invalid or missing data from the rocker arm control module A over the vehicle's network. The computer detected that the messages from this module were either absent, corrupted, or outside the expected range, so it flagged the data as invalid.

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

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message
  • Often no symptoms besides the warning light, especially if the fault is intermittent
  • Reduced engine performance or rough running if the rocker arm control module affects valve timing
  • Limp mode or reduced power mode activated by the engine control module
  • Intermittent stalling or hesitation during acceleration
  • Other communication-related warning lights or messages on the dashboard

Common causes, most likely first

  1. Faulty rocker arm control module A or its internal circuitry
  2. Damaged or corroded wiring harness or connectors between the module and the network
  3. Poor electrical connections at the module, including loose ground or power supply
  4. Network communication bus faults, such as a short or open in the CAN (Controller Area Network) lines
  5. Low battery voltage or charging system issues causing modules to misbehave
  6. Software or calibration errors in the rocker arm control module or engine control module
  7. Water intrusion or physical damage to the module or its connectors

How to diagnose and fix it

  1. Verify battery voltage and charging system performance, as low voltage can cause communication errors
  2. Inspect and clean the rocker arm control module connectors and wiring for corrosion or damage
  3. Check network communication bus integrity with a scan tool and oscilloscope if available
  4. Perform a wiggle test on the harness while monitoring live data for the module
  5. Reprogram or update the rocker arm control module and engine control module with the latest software
  6. Replace the rocker arm control module if internal failure is confirmed
  7. Repair or replace damaged sections of the wiring harness or connectors

Rocker Arm Module Data Faults You Might Miss

  • A weak or failing battery often causes invalid data codes across multiple modules, so always load-test the battery before condemning the rocker arm control module.
  • Corroded ground connections can create voltage drops that corrupt network messages, mimicking a failed module.
  • Intermittent faults may only appear under specific conditions like vibration or temperature extremes, so a road test with live data monitoring is essential.
  • The rocker arm control module may share a communication bus with other modules, so a fault in one module can affect data from others.
  • After replacing the module, reprogramming or calibration is often required for proper operation, and skipping this step can leave the code stored.

Can I keep driving with U041C?

If the vehicle runs normally, you can drive it to a repair shop, but avoid heavy acceleration or towing until the fault is diagnosed. If the engine runs rough or enters limp mode, limit driving to essential trips and have it inspected promptly.

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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