P0651 Fault Code

Sensor Reference Voltage B Circuit/Open

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0651 fault code indicates a problem with the Sensor Reference Voltage B Circuit. This issue arises when the voltage reference for a specific sensor is either too low, too high, or is open-circuited, leading to incorrect readings or a failure of the sensor to function properly.

• Definition: A fault in the reference voltage circuit meant to provide power to various sensors in the vehicle's system.
• Impact: Can lead to erroneous data being sent to the engine control unit (ECU), impacting performance and emissions.

What are the symptoms of the P0651 code?

Symptoms of the P0651 fault code may include:

• Check Engine Light illuminated on the dashboard.
• Poor engine performance, including rough idling or stalling.
• Increased fuel consumption or degraded fuel economy.
• Unusual sensor readings from affected components, leading to potential erratic behavior in vehicle systems.

What causes the P0651 code?

Common causes for this fault code include:

• Broken or damaged wiring in the reference voltage circuit.
• Faulty sensors that draw too much current or have internal shorts.
• Poor connections or corrosion at connectors affecting voltage supply.
• Issues with the ECU, such as software bugs or internal faults.

How to fix P0651?

To resolve the P0651 fault code, the following steps should be taken:

• Inspect wiring and connectors associated with the Sensor Reference Voltage B circuit for any visible damage or corrosion.
• Test voltage at the affected sensor's connector to determine if it matches the manufacturer's specifications.
• Replace any faulty sensors that are drawing excessive current or are shorted.
• If the wiring and connectors are in good condition, consider reprogramming or replacing the ECU, if necessary.