P05F3Exhaust Aftertreatment Power Relay Control Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- A power relay, switched by the engine module through an output driver, feeds aftertreatment consumers such as the DEF pump, tank and line heaters and possibly NOx sensors or the SCR module. CARB requires such outputs to be checked for circuit faults and function. P05F3 means the driver detects an open relay control (coil) circuit. Ford's comparable relay check flags 'driver on but 0 V' or a heater relay current below 0.2 A, within 5 s. Chrysler (FCA) lists this code among those that trigger the DEF inducement: a 'Service DEF System' warning, a countdown after 50 miles and no restart after 150 miles (P241D). If the relay fails, heaters, pump and SCR control drop out and dosing stops.
- What you may notice
- Check engine light on
- DEF/AdBlue warning, possibly countdown to no-restart
- Follow-up codes for heaters, pump or NOx sensor supply
- Likely causes
- LikelyRelay missing, coil open or not seated properly
- PossibleCorroded connector or relay socket
- PossibleHarness damaged
- RareOutput driver in the engine module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.