Fuel Pump Control Circuit High Voltage
Code P0629 indicates that the PCM has detected a high voltage condition in the fuel pump control circuit. This typically means the voltage at the fuel pump driver module or relay is above the expected range, often due to a short to power, a faulty relay, or a wiring issue. The fuel pump may run continuously or not at all, affecting engine performance.
01. Most Common Causes
- Short to power in fuel pump control circuit
- Faulty fuel pump relay or driver module
- Corroded or damaged wiring/connectors
- Failed PCM (rare)
02. Symptoms You Will Notice
- Engine cranks but won't start
- Check Engine Light illuminated
- Poor engine performance or stalling
- Fuel pump running continuously
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0629 is present.
Step 2: Inspect fuel pump relay and fuse for damage.
Step 3: Check voltage at fuel pump connector with key on; should be 12V for 2 seconds then drop.
Step 4: Test continuity and shorts in wiring between PCM and fuel pump.
Step 5: If wiring is good, replace fuel pump relay or driver module.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The fuel pump may fail or cause a fire hazard. Have the vehicle towed to a shop.
How much does it cost to fix?▼
Typically $50-$150 for parts like a relay or wiring repair, plus diagnostic labor.