C0561 code meaning
Vacuum Sensor A/B Correlation
What C0561 means
Where two vacuum signals describe the brake booster supply, the module expects them to track each other; C0561 means sensor A and sensor B disagree beyond the allowed band. No maker documents this code number publicly. The principle is patented: Ford compares the booster vacuum sensor with a second reservoir sensor after the vacuum pump stops and flags a sensor mismatch; GM checks the booster sensor against manifold vacuum at closed throttle and marks it biased high or low after set times. Sensors such as HELLA's run on 5 V and output 0.5–4.5 V. GM uses C0561 differently: in its brake modules it means stability control was disabled because another module reported a fault. Brake assist and stop/start may be limited.
C0561 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0561
- Brake or stability warning lamp
- Electric vacuum pump runs too often or not at all
- Stop/start or brake assist unavailable on some cars
Common causes of C0561
- Most likelyOne vacuum sensor drifting or reading offset
- PossibleLeaking or kinked vacuum hose or check valve between the two measuring points
- PossibleCorroded connector or damaged wiring on one sensor
- Less likelyUnstable 5 V reference or ground shared by the sensors
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Vacuum sensor aVacuum sensor b
What each part of C0561 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 61 | The exact fault in that area. |
What to do next
- Note C0561 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 C0561
What does C0561 mean?
C0561 means "Vacuum Sensor A/B Correlation". Where two vacuum signals describe the brake booster supply, the module expects them to track each other; C0561 means sensor A and sensor B disagree beyond the allowed band. It is a generic code, so it means the same on every make.
Is it safe to drive with C0561?
Drive gently and only to a workshop. With C0561 the car can go into limp mode (reduced power) to protect itself.
Will C0561 fail an emissions test?
C0561 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 C0561 to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will C0561 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.