P1231 – Fuel Pump Secondary Circuit Low
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Symptoms
- Hard starting
- Intermittent stall
- Loss of power
- Long crank time
- Check engine light
Causes
- High resistance wiring
- Corroded connectors
- Weak relay contacts
- Poor ground
- Control module issue
Diagnosis
- Measure circuit voltage drop
- Inspect connectors
- Check grounds
- Test relay under load
- Scan live data
Repair
- Repair or replace wiring
- Clean or replace connectors
- Replace relay
- Improve grounds
- Update ECU if needed