U0128 Lost Communication with Park Brake Module
Diagnostic trouble code U0128 indicates that the engine control module (ECM/PCM) has lost communication with the park brake control module over the CAN (Controller Area Network) data bus. This module controls the parking brake, especially in vehicles equipped with an electronic parking brake (EPB) system. The loss of communication can be caused by faults in the CAN bus wiring, issues with the park brake module itself, or power/ground problems affecting the module.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Open or short circuit in the CAN bus wiring
- Corroded, loose, or damaged connector at the park brake control module
- Internal failure of the park brake control module
- Blown fuse or poor ground connection to the park brake module
- Fault in the master control module (ECM/PCM) that manages communication
- Incorrect termination resistance on the CAN bus
3. Symptoms You Will Notice
- Parking brake warning light illuminated on the dashboard
- Electronic parking brake may not engage or disengage
- Possible inability to shift out of Park (in some vehicles)
- Other communication-related codes may be present
4. Step-by-Step Diagnosis
Scan for all stored codes and note any related CAN bus codes
Visually inspect the park brake module connector for corrosion or damage
Check the CAN bus wiring for opens, shorts, or high resistance using a multimeter
Verify power and ground at the park brake module (check fuses and relay)
Test CAN bus termination resistance (should be ~60 ohms with modules connected)
If wiring and power are OK, suspect a faulty park brake module or ECM/PCM
5. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. The electronic parking brake may fail to engage or disengage, which could lead to a roll-away or inability to park safely. Have the vehicle diagnosed and repaired immediately.
How much does it cost to fix?▼
The cost varies widely depending on the root cause. A simple fuse or wiring repair may cost $100-$300, while replacing a park brake control module can range from $400 to $800 or more, including labor and programming.