P0628
Fuel Pump A Control Circuit Low
Powertrain Fuel and Air Metering Fuel pump control circuit 🟡 Moderate — Fix within a week
💬
What This Actually Means
In plain language — no jargon

The ECU detected that the fuel pump isn't receiving enough electrical power or the control signal is too weak. Think of it like a dimmed light switch—the pump needs full power to run properly, but it's only getting a partial signal.

⚡
Symptoms You May Notice
3 known symptoms for this code
Engine cranks but won't start or starts intermittently
Loss of fuel pressure; vehicle stalls while driving
Check Engine Light illuminated on dashboard
🔬
Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors the voltage and current supplied to the fuel pump relay control circuit. It expects a clean ground signal and adequate voltage when the pump should be running. If voltage drops below the minimum threshold or the ground circuit has excessive resistance, the ECU logs this fault.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Fuel Pump Control Voltage 12V+ at relay coil during cranking/running Below 10.5V or unstable signal
Ground Circuit Resistance Less than 0.5 ohms Greater than 1.0 ohm (excessive voltage drop)
🔧
Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Fuel pump relay
Locate the relay in the engine bay fuse box, swap it with an identical relay from another circuit to test; replace if faulty.
2
Battery and battery terminals
Clean corroded battery terminals with a wire brush and ensure battery voltage is above 12V; charge or replace battery if needed.
3
Fuel pump wiring harness and connectors
Inspect pump connectors and wiring for corrosion, loose terminals, or damaged insulation; repair or replace compromised sections.