OBD Exhaust Aftertreatment Power Relay Control Circuit Stuck On
What it means
P05F6 stands for Exhaust Aftertreatment Power Relay Control Circuit Stuck On. P05F6 is a P code, so the fault sits in the engine, transmission and emissions systems. For P05F6, the second digit places it in speed and idle control. For P05F6, work through the cause list below, cheapest checks first.
Where it lives
For P05F6, the relay sits on the circuit this code reports. The description of P05F6 reports a fault at the relay.
What to check first
For P05F6, pull the connector and inspect the terminals for spread, corrosion or backed-out pins before testing anything else.
Check these first
- P05F6: Faulty sensor or actuator in the control circuit
- P05F6: Wiring, connector, or fuse problem for the affected output
- P05F6: Low or unstable system voltage from the battery or charging system
- P05F6: Failed PCM/ECM or a software error
- P05F6: Poor ground connection for the control module
What to do next
P05F6 is a fault in the speed and idle control system. The steps below are general, so what actually failed on your vehicle may not be what P05F6 names.
- P05F6: Verify battery voltage and charging system health first
- P05F6: Read all related module codes with an OBD-II scanner
- P05F6: Inspect wiring, connectors, and grounds for the affected circuit
- P05F6: Test the sensor or actuator with live data and actuation commands
- P05F6: Check for PCM software updates or TSBs before replacing modules
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.