What it means
The vacuum reservoir control circuit reads stuck high — short to battery voltage or open coil. The driver cannot pull the line low to actuate the valve/motor.
At a glance
- Usually lights the check-engine light
How it works
The vacuum reservoir control circuit carries the command that operates a valve or pump to maintain stored vacuum. This code sets when the circuit stays higher than expected, such as from a short to power, an open actuator coil, or a poor connection that prevents the controller from pulling the circuit low to operate the device.
Common causes
Most likely first.
- Control wire shorted to battery voltage
- Open coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Vacuum-operated functions may work inconsistently
- Brake pedal may feel harder if brake-assist vacuum is affected
How to diagnose it
- Review freeze-frame data and any available actuator command or vacuum readings to determine when the circuit failed to respond.
- Inspect the valve or pump connector for corrosion, loose terminals, or signs of heat damage.
- Check the harness for a control wire shorted to battery power or rubbed through near a power source.
- With the circuit isolated as specified by the manufacturer, test the actuator coil or motor for an open circuit and check the control wire for continuity.
- If the actuator and wiring are sound, test the controller’s ability to switch the circuit against the manufacturer’s specification.
Common fixes
- Repair a control wire shorted to battery power.
- Restore a clean, tight connection at corroded or loose terminals.
- Replace an open valve coil or pump motor.
- Repair the controller output only after verifying the actuator and harness.
Can I keep driving?
If the brake pedal becomes hard or brake assist is reduced, stop driving and arrange recovery. If braking feels normal, make only a cautious, short trip for repair, because the valve or pump may not maintain vacuum for brake assist or other supported systems.
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.