What it means
The exhaust aftertreatment power relay control circuit is detected as stuck on. The code does not establish that the electronics remain powered after key-off or that the battery will drain.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The exhaust aftertreatment power relay switches power to emissions-control equipment in response to a control signal. The module monitors whether the relay control circuit turns off when expected and sets P05F6 when it detects the circuit stuck on. This does not establish that the equipment stays powered after key-off or that the battery will drain.
Common causes
Most likely first.
- Relay contacts stuck closed
- Control circuit fault keeping relay energized
Symptoms
- Check-engine light or emissions warning may illuminate
- Aftertreatment system fault message may appear
How to diagnose it
- Record freeze-frame data and check live relay command and status to see whether the circuit remains on after the module commands it off.
- Inspect the relay and socket for stuck or heat-damaged contacts, corrosion, and loose or misaligned terminals.
- Check the relay control harness for a short to power and verify its routing and connector condition.
- Compare the module command with voltage at the relay control terminal during on and off states using the wiring diagram.
- If the circuit stays on, isolate the relay and control harness as specified to distinguish stuck relay contacts from a wiring or module output fault.
Common fixes
- Replace a relay confirmed to have contacts stuck closed.
- Repair control wiring shorted to a power source.
- Clean or repair damaged relay socket terminals.
- Repair a confirmed module control-output fault after testing the relay and harness.
Can I keep driving?
The code does not by itself mean the system stays powered after key-off, but incorrect relay operation can affect aftertreatment control. Limit driving if emissions warnings or a countdown appear, and have the relay circuit checked promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.