Code
U05C1
Generic
U — Network/User
Invalid Data Received From Active Radiator Air Flow Control Module A
Views:
UK: 17
EN: 32
RU: 23
AI status
Completed
Completed
100%
Causes
- Faulty Active Radiator Air Flow Control Module (hardware or internal software error)
- Damaged wiring or poor connector connection to the module (power, ground, CAN lines)
- CAN/LIN bus communication fault (bus errors, missing termination, high bit errors)
- Intermittent power supply or ground to the module
- Configuration, calibration, or software mismatch after module replacement or update
- Other module on the bus sending corrupted/invalid messages
Symptoms
- MIL/Check Engine light or dash warning lamp
- Radiator shutter or airflow flaps stuck, slow, or unresponsive
- Abnormal engine temperature regulation (overcooling or overheating)
- Reduced fuel economy or changed HVAC/engine performance due to cooling control fallback
- Stored U-codes or other communication DTCs on scan tool
- Intermittent or permanent loss of data for radiator air flow parameters on scanner
What to check
- Use a scan tool to read U05C1 code details, freeze frame and related codes; attempt to communicate directly with the radiator air flow control module
- Inspect module connector and wiring for corrosion, damage, bent pins, or moisture
- Check module supply voltage (battery +12V) and ground integrity at the connector
- Check CAN bus for errors: verify CAN High/CAN Low voltages with key on, engine off and scan bus traffic
- Measure termination resistance across CAN_H and CAN_L (approx. 60 ohms total) with ignition off
- Check for other U-codes indicating network problems (U0100, U0073, U0401, etc.)
Signal parameters
- Module supply: typically ~12 V with ignition on; no significant voltage drop under load
- Module ground: near 0 V; check for high resistance or voltage on ground circuit
- CAN bus idle (recessive) voltages: ~2.5 V on each CAN line (CAN_H and CAN_L) — measurement should be done with a proper meter or oscilloscope
- CAN bus dominant state: observable differential between CAN_H and CAN_L when data is transmitted (use oscilloscope to confirm clean frames)
- Expected CAN data rates: commonly 250 kb/s or 500 kb/s depending on vehicle — verify protocol and data presence with scan tool or scope
- Termination resistance: about 60 ohms between CAN_H and CAN_L (two 120 ohm terminators in parallel)
Diagnostic algorithm
- Record freeze frame and full list of stored codes; note any network-related codes.
- Attempt to communicate with the Active Radiator Air Flow Control Module using a manufacturer-capable scan tool. Note whether the module responds and whether data values appear plausible.
- Visually inspect the module, connector, and wiring harness for damage, corrosion, water ingress, or disconnected pins. Repair any physical faults.
- With ignition on, measure module supply and ground at the connector. Repair high-resistance supply/ground circuits as needed.
- Check CAN bus voltages at the module connector: verify recessive voltages (~2.5 V) and presence of data using a scan tool or oscilloscope. Look for excessive bus errors or a bus-off condition.
- Measure termination resistance across CAN_H and CAN_L with ignition off; correct missing or incorrect termination.
- If wiring and bus are good but communication/data remain invalid, update or reflash module software/calibration per manufacturer service information.
- If software update does not restore communication and all vehicle-side checks pass, consider replacing the Active Radiator Air Flow Control Module. Reconnect, clear codes and road/test to confirm repair.
- After repair, verify no additional network DTCs and that radiator air flap operation and engine temperature control are normal.
Likely causes
- Loose/corroded connector at radiator air flow module
- Open/short on CAN High or CAN Low between module and network
- Module not receiving stable 12V supply or poor ground
- Module firmware fault or corrupted configuration
- Network termination or wiring harness damage localized near radiator area
Fault status
Status
Invalid Data Received From Active Radiator Air Flow Control Module A — communication or data integrity fault detected on module A
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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