Lost Communication with Special Purpose Module A
Diagnostic trouble code U0259 indicates that the special purpose control module 'A' has lost communication on the vehicle's CAN (Controller Area Network) bus. This code falls under the SAE J2012 standard for network communication faults (U0000-U0299). The special purpose module refers to auxiliary or non-standard modules such as conversion systems, specialized body equipment, or vehicle-specific function modules that are not part of the main powertrain systems. The loss of communication can be intermittent or permanent, preventing the module from sending or receiving necessary data for proper system operation.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty CAN bus wiring (open circuit, short to ground or battery)
- Corroded, loose, or disconnected connector at the special purpose module
- Internal failure of the special purpose module 'A' (damaged CAN transceiver)
- Faulty master control module or gateway on the data bus
- Missing or incorrect CAN bus termination resistor
- Electromagnetic interference in the communication harness
- Low battery voltage or power supply issue to the module
3. Symptoms You Will Notice
- Malfunction indicator lamp (MIL) illuminated
- Inoperative or erratic operation of systems controlled by the special purpose module
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Inspect CAN bus wiring and connectors for damage, corrosion, or loose connections
Check battery voltage and module power supply
Test CAN bus termination resistance (should be ~60 ohms between CAN-H and CAN-L)
Verify communication with other modules; if multiple modules are offline, suspect a bus fault
If isolated to one module, attempt to communicate directly with the special purpose module; if no response, replace module
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but systems controlled by the special purpose module may not function properly. It is recommended to diagnose and repair the issue promptly to avoid further problems.
How much does it cost to fix?▼
Repair costs vary widely depending on the cause. Wiring repairs can range from $100 to $300, while module replacement can cost $200 to $800 or more, including labor and diagnostics.