P0629
Fuel Pump A Control Circuit High
Powertrain Fuel and Air Metering Fuel pump control 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The ECU detected the fuel pump control signal is too high, like a stuck accelerator pedal that won't stop sending signals. This means the pump relay or wiring is likely shorted or faulty, preventing the ECU from properly controlling fuel delivery.

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Symptoms You May Notice
3 known symptoms for this code
Engine cranks but won't start or starts intermittently
Fuel pump runs continuously even with ignition off
Check Engine Light illuminated
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the voltage feedback from the fuel pump control circuit. It expects a specific voltage range when commanding the pump on and off. A high voltage condition indicates the control signal is stuck high or the pump relay is not responding properly to ECU commands.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Fuel pump control voltage 0-5V with proper PWM cycling Sustained voltage above expected threshold or stuck high
Pump current draw 4-8 amps during operation Current feedback abnormally high or unable to be controlled
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Fuel pump relay
Locate and replace the fuel pump relay in the engine bay fuse/relay box.
2
Fuel pump control wiring harness
Inspect wiring for shorts, corrosion, or damaged insulation between ECU and pump; repair or replace as needed.
3
Fuel pump assembly
Replace the fuel pump if relay and wiring test normal but fault persists.