P06B4
Sensor Power Supply B Circuit Low
Sensor power supply
Generic OBD-II
High
What it means
P06B4 means the engine computer sees a lower-than-expected voltage on its "B" sensor power supply. Multiple sensors draw from this supply, so a low reading — usually a short to ground or a failed sensor dragging it down — can set several sensor codes at once and force a reduced-power mode. It rarely stops the car outright but should be diagnosed promptly.
High
Can I keep driving? Often drivable but unpredictable — the low supply can affect several sensors and push the engine into limp mode, so get it diagnosed soon.
Common symptoms
What you'll notice
- Check-engine light on, often with several sensor codes set together
- Rough running, hesitation, or reduced power
- Reduced-power or limp mode
- Intermittent stalling in some cases
Common causes
Most likely first
- A sensor shorting the shared power supply to groundLikely
- Short to ground or chafed wiring in the sensor power supply B circuitCommon
- Corroded or loose connector on the supply circuitCommon
- Internal ECM/PCM fault on the sensor power supplyLess often
How to diagnose & fix
Work through it in order
- Scan for all stored codes — sensors fed by supply B usually set codes together and point to the shared circuit.
- Unplug sensors on that supply one at a time to see if the voltage recovers, isolating a shorted sensor.
- Inspect the supply wiring for chafing or a short to ground and check connectors.
- If wiring and sensors are good, the ECM/PCM power supply is suspect. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P06B4?+
Sometimes short term, but because it can affect several sensors and trigger limp mode, get it diagnosed soon.
Can I just clear P06B4?+
It will return until the shorted sensor or wiring on the supply B circuit is repaired.
Related codes
Often seen with P06B4
Read & clear P06B4 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX