U0243: Lost Comms with Parking Assist Module B
Diagnostic trouble code U0243 indicates a loss of communication between the engine control module (ECM) or body control module (BCM) and the Parking Assist Control Module B. This means the primary module is not receiving the expected data signals from the secondary parking assist module over the vehicle's communication network (such as CAN, LIN, or a proprietary data bus). The code sets when the main control module detects an interruption in periodic data exchange. While the parking assist system may become inoperative, this network-related code (Class U) typically does not affect drivability, but it does disable active safety features related to parking.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Parking Assist Module B lacks power (blown fuse or faulty relay)
- Parking Assist Module B is damaged or has an internal failure
- Communication bus wiring is open or shorted
- Poor connection or corroded terminals at Module B's harness connector
- Poor ground connection at the parking assist module
- Faulty bus termination resistor (if applicable)
- Severe electromagnetic interference on the data wiring
3. Symptoms You Will Notice
- Parking assist system (rear or front sensors) does not function
- Warning light or message on the dash indicating parking assist fault
4. Step-by-Step Diagnosis
Check for blown fuses and confirm power and ground at Parking Assist Module B
Inspect the communication bus wiring and connectors for damage, corrosion, or loose pins
Verify the module's ground connection is clean and tight
Test the bus termination resistance (if applicable) per vehicle specifications
If power, ground, and wiring are okay, suspect a faulty Parking Assist Module B and replace it
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive because the code does not affect engine or transmission operation. However, parking assist features will be disabled, so you should rely on mirrors and cameras when parking.
How much does it cost to fix?▼
The cost can range from $100 to $500 depending on the root cause. A simple fuse or wiring repair may be under $150, while replacing the parking assist module can cost $200–$500 including labor.