U011C Lost Communication with Rocker Arm Control Module B
The U011C code indicates a loss of communication on the CAN bus with the Rocker Arm Control Module 'B'. This module manages variable valve timing (VVT) or variable valve lift systems (such as VTEC, VVT-i, MultiAir, etc.) for the designated bank or actuator set 'B'. The fault means the ECU/PCM is not receiving valid signals from this module for a set period, disrupting precise valve control on that engine bank.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty Rocker Arm Control Module 'B' (internal damage or communication failure)
- Open or short circuit in the CAN bus wiring to module 'B'
- Corroded, damaged, or disconnected module connectors
- Faulty CAN bus termination resistor
- Power supply issue (low voltage or poor ground to the module)
- Faulty master ECU/PCM (less common)
3. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or misfire
- Reduced engine performance or power loss
- Poor fuel economy
- Engine may run in fail-safe mode
4. Step-by-Step Diagnosis
Scan for other related codes and document freeze frame data
Inspect the Rocker Arm Control Module 'B' connectors and wiring for damage, corrosion, or loose connections
Check CAN bus voltage and resistance at the module connector
Verify power and ground supply to the module
Test the module by swapping with a known good one if possible, or perform manufacturer-specific tests
5. Frequently Asked Questions
Is it safe to drive?▼
It is not recommended to drive with this code as it can cause engine performance issues and potential damage. Have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely, typically ranging from $200 to $1,200 depending on the root cause (wiring repair vs. module replacement) and labor rates.