All codes
Sensor Reference Voltage B Circuit/Open
P0651 relates to sensor reference voltage b circuit/open. Check the fault conditions and vehicle-specific procedure before replacing parts.
What you may notice
Symptoms
- 01Warning light may illuminate
- 02Related system function may be impaired
- 03Vehicle-specific symptoms vary
Where to look first
Common causes
- 01Low or unstable supply voltage, fuse or relay fault, poor ground, or wiring damage
- 02Related wiring, connector, power or ground fault
- 03Vehicle-specific mechanical or control issue
A sensible sequence
Best diagnostic order
- 01Record stored and pending codes and freeze-frame data
- 02Measure battery and charging voltage under load and compare with scan data; test the named circuit, fuse, relay, grounds and connectors.
- 03Confirm measured values against the vehicle service information
- 04Retest under the conditions that set the code
Step by step
What to check and repair
- 01Measure battery and charging voltage under load and compare with scan data; test the named circuit, fuse, relay, grounds and connectors.
- 02Repair the verified cause and confirm the code does not return
Read the signals
Live-data clues
System voltage and circuit command
- Typical behavior
- Consistent with the vehicle specifications and operating conditions
- Possible clue
- A dropout or implausible value can localize the fault
| Parameter | Typical behavior | What it can suggest |
|---|---|---|
| System voltage and circuit command | Consistent with the vehicle specifications and operating conditions | A dropout or implausible value can localize the fault |
What P0651 means
Sensor Reference Voltage B Circuit/Open. This diagnostic trouble code identifies a detected condition; it does not by itself identify the failed part.
Diagnostic direction
Measure battery and charging voltage under load and compare with scan data; test the named circuit, fuse, relay, grounds and connectors.
Before clearing the code
Record stored and pending codes and freeze-frame data. Confirm specifications and tests for the exact vehicle. Repair the verified cause, then repeat the appropriate monitor or drive cycle.