Lost Communication with Special Purpose Module D
Diagnostic trouble code U025C indicates a loss of communication with a special purpose control module identified as 'D' on the vehicle's data bus. This code is set when the module storing the code fails to receive valid messages from module D for a manufacturer-defined period, disrupting functions that depend on that module. The issue can stem from a faulty module, wiring problems, or network faults.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty special purpose control module D (sender or receiver)
- Open or short circuit in the CAN/LIN bus wiring (to ground or battery)
- Damaged or out-of-spec CAN bus termination resistor (typically 60-120 ohms)
- Power or ground failure at module D
- Electromagnetic interference affecting signal integrity
- Corrosion or damage at module or harness connectors
- Software or calibration mismatch after module replacement
3. Symptoms You Will Notice
- Malfunction indicator lamp (MIL) illuminated
- Inoperative or erratic operation of systems controlled by module D
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Check for technical service bulletins (TSBs) related to U025C
Inspect wiring and connectors for damage, corrosion, or loose connections
Measure CAN bus termination resistance at the diagnostic connector (should be 60-120 ohms)
Verify power and ground at module D
Test module D communication using a scan tool or oscilloscope
5. Frequently Asked Questions
Is it safe to drive?▼
Driving may be possible but is not recommended as it can cause unpredictable behavior of systems relying on module D. Have the vehicle diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary widely, typically ranging from $100 for a simple wiring repair to $800 or more for module replacement and programming.