Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
A/F Sensor Heater Relay: Inspection
- REMOVE RELAY BOX COVER
- REMOVE A/F SENSOR HEATER RELAY (Marking: A/F)
- INSPECT A/F SENSOR HEATER RELAY
- Inspect the relay continuity.
- Using an ohmmeter, check that there is continuity between terminals 1 and 2.
If there is no continuity, replace the relay.
- Check that there is no continuity between terminals 3 and 5.
If there is continuity, replace the relay.
- Using an ohmmeter, check that there is continuity between terminals 1 and 2.
- Inspect the relay operation.
- Apply battery positive voltage to terminals 1 and 2.
- Using an ohmmeter, check that there is continuity between terminals 3 and 5.
If there is no continuity, replace the relay.
- Inspect the relay continuity.
- REINSTALL A/F SENSOR HEATER RELAY
- REINSTALL RELAY BOX COVER
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.