P0561 code meaning
System Voltage Unstable
What P0561 means
The module measures its own supply voltage. CARB allows other monitors to be suspended below 11 V, and above a maker's threshold only if the voltage itself is diagnosed – that is what these codes record. GM's engine modules and Ford's PCM set them without warning lamp. GM interprets P0561 as a difference between the module's two supply inputs: permanent battery and switched ignition supply may differ by at most 3 V, otherwise it sets after 50 of 63 samples. In the engine module that is type C without warning lamp, in GM's 9-speed transmission module type A with the lamp after one trip. Other makers use it for a fluctuating voltage.
P0561 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0561
- Further voltage or communication codes
- Transmission warning or check engine light (GM transmission module)
- Sporadic dropouts of electrical functions
Common causes of P0561
- Most likelyFuse, relay or line of the ignition supply (voltage drop)
- PossibleLoose or corroded connector or ground at the module
- PossibleVoltage regulator fluctuating
- PossibleBattery terminal loose
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
BatteryAlternatorModule power supplyEngine control module
What each part of P0561 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 61 | The exact fault in that area. |
What to do next
- Note P0561 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 P0561
What does P0561 mean?
P0561 means "System Voltage Unstable". The module measures its own supply voltage. It is a generic code, so it means the same on every make.
Is it safe to drive with P0561?
P0561 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0561 fail an emissions test?
P0561 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0561 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0561 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.