Error code

OBD2 P0651

OBD2P0651
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Sensor Reference Voltage 'B' Circuit/Open.

Severity

moderateCan drive, but may experience performance issues.

Summary

P0651 indicates a sensor reference voltage 'B' circuit has an open connection. This affects sensors connected to the second reference voltage circuit.

Symptoms

  • Illuminated warning light
  • Potential driveability issues

Common Causes

  • Damaged, shorted, burnt, disconnected, or corroded wiring and connectors
  • Defective sensors connected to the 'B' reference voltage circuit
  • Blown fuses or defective relays
  • Failed PCM (rare)

Diagnosis

  1. Record all fault codes and freeze frame data.
  2. Identify sensors connected to the 'B' reference voltage circuit.
  3. Check if PCM is generating correct 5-volt current in the 'B' circuit.
  4. Disconnect wiring from each sensor while monitoring scanner for changes.
  5. Test continuity of reference circuits between connectors and ground.
  6. Test internal resistance of affected sensors.

Fixes

  • Repair or replace damaged wiring/connectors
  • Replace defective sensors

FAQ

What does P0651 mean?

P0651 indicates an open circuit in the sensor reference voltage 'B' circuit, affecting multiple engine and other sensors.

How do I diagnose P0651?

Diagnose by checking wiring/connectors for damage, testing continuity of circuits, and verifying internal resistance of affected sensors.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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