Powertrain
generic / SAE
P0651
Sensor Reference Voltage B Circuit Open
The 5-volt sensor reference rail B is open — the module supplies no voltage on this circuit. Every sensor powered from reference B loses its supply and reads invalid, so the ECU substitutes default values and may limit engine operation. Causes: a broken reference wire, a disconnected connector, or an internal open in the module's voltage regulator for rail B.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number6 / 51
Possible causes
- Open in shared reference rail high
- Pin pushed back out of connector body low
- Cracked solder joint inside the module or sensor low
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 80–400 €
- Estimated time: 0.5–2 h
- Component: sensor reference voltage b
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012