What it means
The electric vacuum pump control circuit reads stuck low — short to ground or low-side driver stuck on. The pump may run continuously, drawing current and overheating, until the ECM disables the channel.
At a glance
- Usually lights the check-engine light
How it works
An electric vacuum pump supplies brake-booster vacuum when engine vacuum is insufficient or unavailable. This code means control circuit A is being held at a low electrical level, often by a short to ground or a driver that remains switched on. The pump may run continuously until the module disables it, risking overheating and loss of reliable brake assist.
Common causes
Most likely first.
- Control wire shorted to ground
- Faulty vacuum pump control module or driver
- Damaged pump connector or harness
Symptoms
- Brake warning light may come on
- Brake pedal may feel harder than usual
- Reduced brake assist may occur
How to diagnose it
- Check whether the pump runs continuously and whether the brake pedal or warning light indicates reduced assist; stop driving if braking feels unsafe.
- Read freeze-frame and live pump command data to determine whether circuit A is being commanded on when the pump keeps running.
- Inspect the pump connector and control harness for rubbed-through insulation, moisture, corrosion, or a wire shorted to ground.
- With the manufacturer's wiring diagram, check circuit A for a short to ground and inspect the pump driver and connector for damage.
- If the harness is sound, test the control-module driver and pump circuit using the manufacturer's procedure before replacing components.
Common fixes
- Repair a control wire in circuit A that is shorted to ground.
- Repair damaged pump wiring or connector contacts.
- Replace a confirmed faulty control module or pump driver.
- Replace the vacuum pump if it has been damaged by continuous operation.
Can I keep driving?
Avoid driving if the pump runs continuously, a brake warning appears, or the pedal becomes hard; continuous operation can overheat the pump and brake assist may become unreliable. Arrange prompt diagnosis, and use safe recovery if braking effort has increased.
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.