P05F2

What it means

P05F2 means the control unit has detected a fault in the supply voltage circuit for the reductant (diesel exhaust fluid) pump, which stays off when it should be switched on. The module commands power to the pump and monitors the circuit, and it saw no supply voltage or no response. The exact circuit layout, such as a relay, fuse or internal driver, depends on the vehicle and engine.

Symptoms

• Engine warning light or an exhaust fluid or SCR system warning on the dashboard
• Message warning of reduced performance or a restricted restart if the fault is not fixed
• Reductant pump not running or not building pressure
• Possible limp mode or reduced power on some vehicles
• Related reductant pressure or dosing fault codes stored alongside

Possible causes

• Blown fuse or faulty relay in the reductant pump supply circuitlikely
• Open circuit, chafed wiring or high resistance in the pump supply or ground wirelikely
• Corroded, loose or water-damaged connector at the pump, relay or control unitlikely
• Faulty reductant pump or integrated supply module drawing no current or failing internallypossible
• Low battery voltage or a poor main power or earth connection affecting the supplypossible
• Fault inside the control unit driver stage that switches the pump supplyrare

How to diagnose

1. Read all stored codes and freeze frame data, noting battery voltage, temperature and whether other reductant or power supply codes are present
2. Check the battery condition and charging voltage, as low voltage can set supply circuit faults
3. Inspect the relevant fuse and relay for the reductant pump using the vehicle wiring diagram
4. Visually inspect the wiring and connectors from the pump to the relay and control unit for damage, corrosion, moisture or pushed-out pins
5. With the pump circuit active (via a bidirectional test if available), check for supply voltage and ground at the pump connector
6. Voltage drop test the supply and ground circuits under load to find high resistance
7. Check the pump's resistance or current draw against the manufacturer's specification, as this varies by model
8. Clear the code and retest to confirm the fault does not return

How to fix

• Replace the blown fuse only after finding and correcting the cause of the overload
• Replace a faulty relay
• Repair or replace damaged wiring and clean or renew corroded connector terminals
• Replace the reductant pump or supply module if it fails electrical checks
• Restore a sound battery, power and earth supply if low voltage is the cause
• Diagnose and repair or replace the control unit only once all wiring and pump faults are ruled out

Can I keep driving?

Nearby codes

• P05F1GenericReductant Pump Supply Voltage Circuit Stuck On
• P05F3GenericExhaust Aftertreatment Power Relay Control Circuit/Open