What it means
Input power line B voltage below expected range. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
The module monitors its B input-power feed to ensure it receives enough voltage to operate. This code sets when voltage on the B feed falls below the expected range, potentially interrupting the module and its communications.
Common causes
Most likely first.
- Weak battery or high supply resistance
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Save freeze-frame data and scan all modules for low-voltage or communication faults to determine whether the B-feed dip was vehicle-wide.
- Check battery condition and charging-system operation, since a weak battery can pull down module supply voltage.
- Inspect the module’s B-feed fuse, connector, wiring, and ground for corrosion, loose terminals, or damage.
- Measure voltage at the B feed during the conditions shown in freeze-frame data and compare it with the manufacturer's specification.
- If the battery and B feed are sound, test voltage drop along the supply path and then inspect gateway routing and CAN termination per the vehicle wiring diagram.
Common fixes
- Clean and tighten corroded battery, B-feed, or ground connections.
- Replace a weak battery if it fails the manufacturer's battery test.
- Repair high-resistance or damaged B-feed wiring or connector terminals.
- Repair a confirmed gateway or CAN network fault if B-feed voltage is correct.
Can I keep driving?
If the module shuts down, limp mode occurs, or warning lights and drivability problems appear, stop when safe and avoid driving further because essential functions may be limited. If symptoms are minor, keep travel short and have the low supply checked promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.