What it means
The ECM detects a low fault on the dc/dc converter current sensor b circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The DC/DC converter supplies low-voltage power from the high-voltage system to the 12-volt electrical system. The control module monitors current sensor B’s signal, and this code sets when that signal is lower than the circuit’s expected range, making the current reading unreliable.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Hybrid or EV system warning light
- Reduced power or limited electric drive
- Charging may be limited
- Reduced electric range
How to diagnose it
- Record freeze-frame data and check live data for current sensor B to confirm the low reading and when it occurs.
- Check for other converter, low-voltage supply, or hybrid-system codes that could explain a shared circuit fault.
- With the vehicle powered down using the manufacturer’s high-voltage safety procedure, inspect sensor B’s signal wiring for chafing or contact with ground.
- Inspect sensor B’s connector for corrosion, damaged terminals, looseness, or moisture that could pull the signal low.
- Test the signal wire for a short to ground and check the sensor and circuit using the manufacturer’s diagnostic procedure; replace the sensor only if wiring and connections are sound.
Common fixes
- Clean and secure corroded or loose sensor B connector terminals, replacing damaged terminals as needed.
- Repair a signal wire that is shorted to ground or otherwise damaged.
- Replace current sensor B if its output remains low with correct wiring and connections.
Can I keep driving?
Avoid relying on the vehicle for long trips if power is reduced or electric drive is limited, and stop if the warning is accompanied by a substantial loss of power. The low sensor signal can interfere with converter control and may limit 12-volt charging or electric range.
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.