OA 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
Wear or soot contamination of the NOx sensor
Air leak or exhaust leak before the sensor
Damaged sensor wires or connector
What you can do yourself
Inspect the NOx sensor connector and wires on the exhaust pipe
Check for an exhaust leak before the sensor
See an auto electrician: sensor check with a scanner
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
OOOleg’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 explanation comes from the error code reference in the AvtoElektrik PRO app.
Meaning for specific makes
The same number can mean different things for different makes. Below is the make-specific meaning.
Volkswagen, Audi, Skoda, Seat: NOx sensor 1 (before the catalyst): signal out of range
Safe to drive
OA 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
Air leak/exhaust leak before the sensor (clamp and gasket at the LP-EGR valve)
NOx sensor wear or soot contamination
Corrosion of the power pin in the 5-pin connector of the sensor module
What you can do yourself
First look for exhaust leaks (soot traces, smoke test)
Check the sensor module connector and the ~12 V supply with the ignition on
Replace the sensor only after checks, then adaptation with a scanner
OOOleg’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”.
OA 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
Faulty front NOx sensor (bank 1, sensor 1)
Damaged wiring or connector under the vehicle
No power to the sensor module (according to the source — 15 A fuse F14)
Non-genuine EGR cleaners contaminate the sensor
What you can do yourself
Check the fuse and the sensor module connector on the frame
Ask the dealer by VIN about service programmes (21E01/21N02)
After sensor replacement — reset the NOx adaptations with a scanner
OOOleg’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”.
Couldn’t fix it yourself? Oleg, an auto electrician, does computer diagnostics and repairs: he comes out anywhere in Almaty or sees you at his workshop.
Oleg’s course “Car computer diagnostics with a scan tool”: how to hook up a scanner, read codes and live data, and use them to find the cause. The first lessons are free.
The reference is kept by Oleg Dmitriev, an auto electrician from Almaty with 26 years of experience: computer diagnostics of cars and trucks, repair of control units (ECUs). Can’t find the cause? Message him.