U111986 - U111986 RCR_R Signal Invalid

Fault Depth Definition

DTC code U111986 RCR_R Signal Invalid belongs to Class U (Universal) communication diagnostic codes in vehicle electronic network architecture, with a core role in monitoring data link integrity between Advanced Driver Assistance Systems (ADAS) internal control units and sensor nodes. This code explicitly points to a state where the vehicle controller cannot validate feedback information received from the right-rear corner radar system. From a system interaction logic perspective, this fault reflects that the control unit cannot receive physical position or detection parameter signals complying with protocol specifications, causing the closed-loop feedback loop to break on the right-rear corner radar side. When the onboard network determines that the transmitted RCR_R signal voltage or data frame checksum does not meet preset logic, the system immediately defines this state as hardware communication abnormality, which is a key diagnostic event in whole vehicle domain controller management.

Common Fault Symptoms

Based on original data definitions and actual vehicle operation performance, the impact of this fault code triggering on driving experience is mainly reflected in the following aspects:

• Adaptive Cruise Control (ACC) function immediately fails or exits service, with the cruise icon on the dashboard turning off and unable to set target speed.
• Drivers may find on highways that the vehicle cannot automatically maintain following distance with vehicles ahead.
• Vehicle auxiliary driving related indicator lights display yellow warnings or red fault prompts, clearly informing that the radar perception system is unavailable.
• Functions relying on this radar for automatic lane changing or blind spot monitoring involving the right-rear side are shielded by system logic to ensure safety.

Core Fault Cause Analysis

According to diagnostic logic and hardware architecture, the causes leading to U111986 RCR_R Signal Invalid can be analytically explained from the following three dimensions:

• Hardware Components: Right-rear corner radar sensor internal signal processing module damage, unable to generate valid RCR_R feedback signals; or radar probe and antenna parts are physically damaged leading to signal source loss.
• Wiring/Connectors: Wiring harness appearing between controller and right-rear corner radar experiencing open circuits, short circuits, or insulation layer damage; CAN bus interface terminal loose, oxidized or poor pin contact causing signal transmission interruption.
• Controller: Communication protocol parsing logic inside host control unit abnormally changed, failing to correctly identify received data frame structures; or software version incompatibility leads to signal checksum algorithm execution failure.

Technical Monitoring and Trigger Logic

The setting of this fault code is based on strict timing, electrical parameters, and network state conditions. Its technical monitoring and trigger logic are as follows:

• Monitoring Target: System continuously monitors the RCR_R signal voltage or data integrity received from the right-rear corner radar to ensure it remains within electrical parameter ranges allowed by the controller.
• Numeric Range: Controller supply voltage must remain stable between $9V$~$16V$. Only under working conditions satisfying this voltage window does the fault judgment logic allow activation.
• Specific Conditions and Time Window: System starts effective monitoring only after vehicle power-up initialization completes for $3s$; and when service detection DTC persists fully for $3s$ before officially locking the fault code. During this process, public CAN bus must remain online and cannot enter busoff (bus off) state.
• Logic Prerequisites: Only under non-factory mode operation (with factory mode turned off) and without controller receiving battery discharge notice from Body Control Module (BCM), does the system determine this signal invalid fault as an effective record.