What it means
Fuel Pump A Control Circuit Low: the control-circuit voltage is below the expected range. Often a short to ground or high resistance in the wiring.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Fuel Pump A's control circuit switches or regulates power to the pump under ECM command. P0628 is set when the monitored control-circuit voltage is lower than expected, which can result from a short to ground, a faulty relay, or resistance at a connector and may interrupt fuel delivery.
Common causes
Most likely first.
- Pump circuit shorted to ground
- Pump relay defective
- Connector pins corroded - high contact resistance
Symptoms
- Engine may crank but fail to start
- Engine may stall or lose power if fuel delivery is interrupted
How to diagnose it
- Save freeze-frame data and check fuel pressure and related pump codes to establish whether the low signal coincided with loss of fuel delivery.
- Inspect Fuel Pump A's fuse, relay, wiring, and connectors for damaged insulation, corrosion, loose pins, or a wire contacting ground.
- Check pump and chassis grounds for a weak or corroded connection.
- Use live data and a meter to compare the commanded pump state with control-circuit voltage during the pump prime and engine operation.
- Test the circuit for a short to ground and excessive connection resistance, then check relay and pump operation against the manufacturer's specification.
Common fixes
- Clean and secure corroded Fuel Pump A connector or ground connections.
- Repair a control wire shorted to ground or damaged by chafing.
- Replace a defective pump relay after verifying the rest of the circuit.
- Replace the fuel pump if testing shows it is causing excessive load or failing to operate.
Can I keep driving?
If the engine loses power, stalls, or will not start, do not continue driving because fuel delivery may fail again. Have it checked before relying on the vehicle, since a stall in traffic can be hazardous.
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.