U011C

Universal

Lost Communication With Rocker Arm Control Module B

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

This code means another vehicle module is not receiving expected communication from Rocker Arm Control Module B. That module is involved in controlling rocker arm operation, which can affect how the engine operates. The code identifies a communication problem, not proof that the module itself has failed. Effects depend on the vehicle and whether it uses this system.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the engine runs very roughly, loses power, stalls, or makes unusual mechanical noise, stop driving when it is safe and arrange an inspection. If the vehicle runs normally, avoid hard acceleration and have the fault diagnosed soon. Exact risk depends on the vehicle and engine.

Common Symptoms

  • The check-engine light or another warning light may be on because the vehicle has detected a module communication fault.
  • There may be no noticeable symptoms if the engine continues to operate normally or the affected control function is not currently apparent.
  • Rough running, reduced power, or changes in engine operation may occur if loss of communication prevents the rocker arm control system from operating as intended.
  • A scan tool may be unable to communicate with Rocker Arm Control Module B, or other modules may store related communication codes.

Common Causes

  • A loose, damaged, corroded, or contaminated connector or wiring connection may interrupt communication.
  • A network wire may be open, shorted, damaged, or affected by a poor connection.
  • The module may have an interrupted power supply or ground, preventing it from communicating.
  • Low or unstable vehicle battery voltage may disrupt module communication.
  • Rocker Arm Control Module B may have an internal fault, but the code alone does not confirm this.

Diagnostic Steps

  1. Note any warning lights, engine-running changes, and when they occur; this information can help distinguish a communication fault with no apparent effect from one affecting engine operation.
  2. Check whether the battery terminals are secure and visibly clean. Low or unstable supply voltage can affect module communication.
  3. With the vehicle off, visually inspect accessible wiring and connectors related to the rocker arm control system for looseness, damage, corrosion, or signs of moisture. Do not disconnect components unless the vehicle-specific service information says it is safe.
  4. If you have a compatible scan tool, record all stored codes and which modules respond before clearing anything. Related codes can help identify a broader power or network issue.
  5. If the engine runs very roughly, loses power, stalls, or makes unusual noise, stop driving when safe and arrange professional diagnosis rather than continuing checks on the road.

When to Call a Professional

Use a scan tool that can communicate with all vehicle modules. Check which modules report communication faults and whether Rocker Arm Control Module B responds. Then inspect its power, grounds, connectors, and network wiring using vehicle-specific service information. Confirm the circuit and network diagnosis before considering module replacement; programming may be required if a module is replaced.

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Commonly Asked Questions

Does U011C prove that Rocker Arm Control Module B has failed?

No. It indicates lost communication with that module. Wiring, connectors, power, grounds, battery condition, or the vehicle network can also prevent communication.

Can I drive with U011C?

It depends on how the vehicle behaves. If it runs normally, arrange diagnosis soon and avoid hard driving. Stop when safe and seek assistance if it runs very roughly, loses power, stalls, or makes unusual mechanical noise.

Why might the code appear without obvious symptoms?

A communication fault may be intermittent, or the engine may continue operating without an obvious change. A scan of all modules can show whether the fault is current and whether other modules report related communication problems.

What should be checked before replacing the module?

Check module power and grounds, connectors, wiring, and the vehicle network using service information for the exact model, year, and engine. The code alone does not identify which part or circuit is at fault.

Browse Available Code Guides

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