P05F6Exhaust Aftertreatment Power Relay Control Circuit Stuck On
- 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. P05F6 is a function check on the load side: the relay stays closed although it is switched off, so the consumers keep their supply, e.g. during after-run. A patent by Delphi describes this kind of check via the voltage at the heater node. No manufacturer document available to us uses this exact code; GM and Ford monitor the same function under their own codes. 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
- Consumers stay powered after switch-off, battery drains
- Likely causes
- LikelyRelay contacts welded or sticking
- PossibleExternal voltage on the load side (short to positive)
- PossibleCorroded connector or relay socket
- 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.