P05F0: Reductant Pump Supply Voltage Circuit High

The electric supply pump in the diesel exhaust fluid (DEF, AdBlue) tank module builds the dosing pressure for the SCR catalyst. Its supply voltage is monitored separately from the pump control circuit (P208A ff); CARB requires SCR components and their outputs to be checked for circuit faults and function. P05F0 means the supply voltage is too high, or voltage is present although the supply is switched off (short to battery). GM's 6.6 L diesel monitors this as P1044 (two trips); Ford flags pump voltage above 16 V or controller voltage above 19 V. No manufacturer document available to us uses this exact code; GM and Ford monitor the same function under their own codes. Without supply the pump cannot build pressure, dosing stops and NOx rises; pressure or SCR efficiency codes may follow.

Symptoms

• Check engine light on
• DEF/AdBlue warning, possibly countdown to no-restart
• Follow-up codes for low DEF pressure or SCR efficiency

Most likely causes

• Pump supply shorted to battery positive in the harness
• Overvoltage from the charging system or a jump start
• Moisture or corrosion causing leakage current in the connector
• Relay or driver does not switch off

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P05F0 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 5: Speed and idle
• F0: Specific fault in that system

Frequently asked questions

Can I keep driving with code P05F0?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P05F0?

The most common causes are: pump supply shorted to battery positive in the harness; overvoltage from the charging system or a jump start; moisture or corrosion causing leakage current in the connector.

Related codes

• P208AReductant Pump A Control Circuit/Open
• P208CReductant Pump A Control Circuit Low
• P208DReductant Pump A Control Circuit High
• P20E8Reductant Pressure Too Low
• P21CBReductant Control Module Supply Voltage Low
• P21CCReductant Control Module Supply Voltage High

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
• fordservicecontent.com: obd summary diesel 2023

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.