What it means
The control module monitors the signal circuit for vacuum sensor A. It sets this code when the circuit is detected as open and the sensor signal is unavailable.
How it works
Vacuum sensor A sends a signal about vacuum used by the brake assist system to the control module. This code sets when the module detects an open in sensor A's signal circuit and cannot obtain a reliable reading.
Common causes
Most likely first.
- Signal wire open
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
Symptoms
- Brake or stability-control warning light on
- Brake assist may be affected
How to diagnose it
- Scan the brake or stability module and check freeze-frame and live data to confirm that vacuum sensor A's signal is absent or unavailable.
- Inspect sensor A's connector for a terminal pushed back, corrosion, water entry, or a loose fit.
- Trace the sensor A signal wire for breaks, damaged insulation, or a poor connection at a splice.
- Use the vehicle wiring information to test continuity through the sensor A signal circuit and its connections.
- If the circuit is intact, test sensor A and the module input for an internal open using the manufacturer's procedure.
Common fixes
- Restore a terminal that has backed out of sensor A's connector.
- Repair a broken or damaged sensor A signal wire.
- Clean or repair loose or corroded connector terminals and splices.
- Replace sensor A or repair a module connection only if testing confirms the fault is internal.
Can I keep driving?
Brake assist may be affected, so the pedal may take more effort and stopping distance may increase. If braking feels abnormal, stop safely and arrange assistance; otherwise drive cautiously and have the sensor A circuit checked soon.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.