P06B3

What it means

P06B3 is a generic code meaning the engine or powertrain control module has detected an open circuit on Sensor Power Supply B, one of the regulated reference voltage outputs (usually 5 volts) that feeds a group of sensors. The control unit saw the supply voltage or current outside the expected range, consistent with a break in the circuit. Which sensors share supply B depends on the make, model and engine.

Symptoms

• Engine warning light on
• Reduced power or limp mode
• Poor or erratic throttle response
• Rough running or hesitation
• Hard starting or no start
• Other sensor fault codes stored at the same time

Possible causes

• Open circuit or damaged wiring between the control unit and one of the sensors on supply Blikely
• Corroded, loose or pushed-out pins in a sensor connector or control unit connectorlikely
• A faulty sensor on the shared supply that has failed internally and pulled the supply out of rangepossible
• Chafed or rodent-damaged loom, or poor repair of previous wiringpossible
• Poor power or earth supply to the control unit affecting its internal reference voltage outputpossible
• Internal fault in the control unit sensor supply driverrare

How to diagnose

1. Read all stored codes and freeze frame data, noting any other sensor circuit codes that point to a shared supply
2. Check the manufacturer wiring diagram to identify which sensors are fed by supply B on this model and engine
3. Visually inspect the related wiring and connectors for chafing, heat damage, water ingress, corrosion and bent or loose pins
4. With the ignition on, check the reference voltage at the affected sensor connectors against the specified value
5. Unplug sensors on the shared supply one at a time to see whether the voltage or the fault returns to normal
6. Carry out continuity and resistance checks on the supply wire from the control unit to each sensor, with the battery disconnected
7. Check the control unit power feeds and earths for voltage drop
8. Clear the code and road test to confirm whether it returns, rechecking live data

How to fix

• Repair or replace damaged wiring, using proper soldered or crimped and sealed joints
• Clean, re-seat or repair corroded or loose connector terminals
• Replace the faulty sensor if it is found to be disrupting the shared supply
• Restore good power and earth connections to the control unit
• Replace or repair the control unit only after all wiring and sensors are proven good, following the manufacturer procedure

Can I keep driving?

Nearby codes

• P06B2GenericSensor Power Supply A Circuit High
• P06B4GenericSensor Power Supply B Circuit Low