A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- The heater inside the A/F sensor
- The A/F sensor heater fuse or relay (A/F HTR, EFI)
- The A/F sensor connector or wiring: corrosion, melted wires near the exhaust
- ECU (rarely)
What you can do yourself
- Check the sensor heater fuse (A/F HTR or EFI) in the under-hood box.
- Inspect the sensor connector and wires near the exhaust manifold: melted or chafed wires are a common cause.
- Choose the new sensor by VIN or by the old part number: an A/F sensor differs from an ordinary oxygen sensor.
Stop and don’t drive on if:
- The Check Engine light is flashing
- The temperature gauge is in the red or the overheating light is on
- The red oil pressure light is on
- Smoke from under the bonnet, a burning or petrol smell
- Strong jerking, knocking from the engine, or the car barely moves
OOleg’s tip: check the connector
Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.
Unplug and inspect connectors with the ignition off.
Find the part on Kaspi ShopBefore buying, check the part number or match the part by VIN in the Kaspi “Garage”.
The A/F sensor is a wideband oxygen sensor fitted before the catalytic converter. Bank 2 exists only on V6 and V8 engines. This is the Toyota and Lexus meaning. On other makes this number means something else: if your car isn’t a Toyota or Lexus, change the make at the top.
Source: Toyota 4Runner 1996–2002 repair manual (ether3al.com), obdadvisor.com
The explanation comes from the error code reference in the AvtoElektrik PRO app.