P0651 code meaning
Sensor Reference Voltage B Circuit/Open
Powertrain system Generic code P06xx codes Check engine light
What P0651 means
The engine module feeds several sensors (camshaft, pedal, pressure sensors) from separate regulated 5 V reference circuits; 'B' is circuit 2. A short at one sensor pulls the whole reference down, so every sensor on it reports at once – unplug them one by one until the reference returns to 4.8–5.2 V. P0651 is the general code for circuit B. GM puts all faults into it: reference outside 4.875–5.125 V or jumping, 19 of 39 counts or 0.19 s in a row, with the lamp in the first trip (2018; GM's 2006 V6 used 10 s and two trips). GM Europe's 2.0 L turbo feeds all four camshaft sensors and pedal sensor 1 from it and also uses P0652/P0653 (1 s or 10 s cumulative). Ford reports reference B only as range/performance P06A7. Expect limp mode if the pedal sensor is affected, and starting problems or stalling if camshaft sensors are.
P0651 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0651
- Check engine light
- Several sensor codes at once (camshaft, pedal, pressure)
- Limp mode, reduced power
- Starting problems or stalling
Common causes of P0651
- Most likelyShort in the wire or sensor of a connected sensor (camshaft, pedal, pressure)
- PossibleChafing or water in harness or connector
- PossibleA sensor signal wire shorted to voltage
- Less likelyModule internal voltage regulator
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Sensor reference voltage circuitSensor wiringEngine control module
What each part of P0651 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 51 | The exact fault in that area. |
What to do next
- Note P0651 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0651
What does P0651 mean?
P0651 means "Sensor Reference Voltage B Circuit/Open". The engine module feeds several sensors (camshaft, pedal, pressure sensors) from separate regulated 5 V reference circuits; 'B' is circuit 2. It is a generic code, so it means the same on every make.
Is it safe to drive with P0651?
Drive gently and only to a workshop. With P0651 the car can go into limp mode (reduced power) to protect itself.
Will P0651 fail an emissions test?
Yes, it can. P0651 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0651 to fix?
Difficulty: medium. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will P0651 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.