Lost CAN Bus Communication with AC/DC Converter 'B'
Diagnostic trouble code U0297 indicates that the vehicle's master control module (PCM/ECM or other) has lost serial data communication with the AC/DC Converter Control Module 'B' over the CAN bus (typically the high-voltage or chassis CAN). This converter is responsible for converting high-voltage alternating current from the motor/generator or external source into low-voltage direct current (12V) to charge the auxiliary battery and power low-voltage systems.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty or internally damaged AC/DC converter control module 'B'
- Loose, corroded, bent, or pushed-back pins in the module or harness connectors
- Loss of power (B+) or ground (GND) at the converter module 'B'
- Internal CAN bus failure in another module causing bus blockage
- Software error or need for reprogramming/update of the master module or converter
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Auxiliary battery not charging or low voltage system malfunctions
4. Step-by-Step Diagnosis
Scan for all stored codes and note any related U-codes or B-codes
Visually inspect the AC/DC converter module 'B' connectors and wiring for damage, corrosion, or loose pins
Check for proper power and ground at the converter module 'B' using a multimeter
Test CAN bus continuity and resistance between the master module and converter module 'B'
If wiring and power are good, suspect a faulty converter module or a software issue; attempt reprogramming or replacement as needed
5. Frequently Asked Questions
Is it safe to drive?▼
Driving is not recommended because the auxiliary battery may not charge, leading to a dead battery and potential loss of critical low-voltage systems. Have the vehicle diagnosed and repaired promptly.
How much does it cost to fix?▼
Repair costs typically range from $200 to $800, depending on whether the issue is a wiring repair, connector replacement, or module replacement. Module replacement and reprogramming can be on the higher end.