Oygen Sensor Replacement

Instructions & Repair

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A defective oxygen sensor means you won’t receive an emissions sticker/inspection pass. The reason for this is that a defective oxygen sensor could distort the emission values. Additionally, the oxygen sensor affects the air-fuel mixture.
A detailed guide for replacing a diagnostic sensor depends on the specific vehicle model and the condition of the sensor. However, this article serves as a general guide you can follow to replace the diagnostic sensor.

Contents
  1. Video for this Article
  2. Step 1: Find the right Sensor
  3. Step 2: Remove the defective Oxygen Sensor
  4. Step 3: Install new lambda sensor (diagnostic sensor)
  5. Step 4: Delete Error Codes and Test Drive
  6. More Articles

Video for this Article

Instructions: Replacing the oxygen sensor (diagnostic sensor)

Step 1: Find the right Sensor

In principle, you need to differentiate between two types of oxygen sensors:

The control probe
The diagnostic probe

Basically you will find the Control sensor BEFORE the catalytic converter and the Diagnostic probe AFTER the catalytic converter. The exact functional description of the two probes can be found in this article:
-> Oxygen Sensor Function

When ordering the new diagnostic probe, you should also check the Correct part number pay attention.
-> Buy on Motintegrator.de *

The diagnostic sensor usually has a longer cable than the control sensor. Depending on the error code, you can locate the respective sensor and gain access.

Fault code diagnostic sensor defective - replace lambda sensor
Fault code: The oxygen sensor (diagnostic sensor is defective) - Diagnostic unit: MUCAR CS4

Also, make sure that the car is turned off and cooled down. The diagnostic sensor to be replaced is usually located immediately after the flexible pipe. First, you need to gain access under the car.

Oxygen sensor position (diagnostic sensor)

If you don't have many options to lift your car, we recommend purchasing ramps. * The ramps also offer you some flexibility. This way, you can work under your car, whether you're in the garage or on a regular outdoor parking spot.

Car access ramp, lifting platform, platform
Arebos XXL car drive-on ramp Lifting platform Car ramp 245 mm drive-on width Drive-on ramp Lifting platform Height-adjustable 2 T (set of 2) *
  • [PRACTICAL] Height-adjustable access ramp from 270 to 375 mm, for numerous cars as well as vans, cars, trailers, etc.
  • [ROBUST] Sturdy steel construction (max. load capacity 2 t) with an approach and drive-over edge on the height-adjustable lifting platform.
  • [EASY TO USE] Lifting and lowering by hydraulic cylinder with safety/pressure relief valve - ideal for repairs and maintenance on cars and motor vehicles.
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*Affiliate links, information in footnote or here.

Step 2: Remove the defective Oxygen Sensor

Next, remove the connections to the sensor. Trace the cable of the oxygen sensor and remove the underbody protection under which the connector is located.

Connecting the diagnostic probe to the vehicle
Diagnostic sensor connector: Usually hidden under the underbody protection

Next, remove the fastening screws or clips that hold the sensor after the catalytic converter. The old oxygen sensor is firmly attached to the pipe. Due to carbon buildup and age, it can be really difficult to remove the oxygen sensor. A adapter can help you grip the oxygen sensor more easily. This adapter* is also used in most workshops and doesn't cost much:

Car access ramp, lifting platform, platform
BGS 1140-22 | Lambda sensor insert | angled | 12.5 mm (1/2″) double square drive | SW 22 mm | slot 11 mm | nut *
  • from lambda sensor special insert set Art. 1140
  • Width across flats: 22 mm
  • Length: 50 mm
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View on Amazon

*Affiliate links, information in footnote or here.
LAmbda sensor change with adapter
Remove the oxygen sensor using the adapter

Once the old sensor is out, you can compare it with the new one to ensure that it has the same size and shape. The old defective oxygen sensor will look something like this:

Old lambda sensor - defective
Worn and defective lambda sensor

INFO BOX:

If it doesn't work to remove the old oxygen sensor even with the adapter, you'll have to get creative. In the video you can see how we got the diagnostic sensor out where the adapter failed. You will need a wrench and a longer iron rod as an extension (leverage).

Replacing the lambda sensor with a wrench
The plug of the old oxygen sensor was pinched off
so that you can reach it with a wrench.

Step 3: Install new lambda sensor (diagnostic sensor)

The installation of the new sensor is done in the reverse order of the removal of the old sensor. Screw the diagnostic sensor back on tightly, route the cable to the connector again, and screw everything back together as it was before. Done.

New lambda sensor (diagnostic sensor)
New oxygen sensor (diagnostic sensor) fitted

Step 4: Delete Error Codes and Test Drive

Now you can delete the existing error code again and start the car. Take a short test drive at low speed and observe how the engine behaves. If you don't notice anything unusual related to the fuel injection regulation, the repair was successful. However, if you notice something and the error code reappears, the cause lies elsewhere. Other possible causes could be:

Wiring to the oxygen sensor plug interrupted.
Wrong probe ordered and fitted
The new oxygen sensor has overheated again (leaking injectors)
Additive or lead-containing gasoline has damaged the new sensor again.

*Favorable offers for Oxygen Sensors can be found here:

5 million spare parts in the range
Trusted Shops certification
Top delivery times of 1 - 2 working days
First-class customer service
Attractive payment options
Buy on Motointegrator.de


* Affiliate links are marked with a *. Nothing changes for you and the offer/price remains the same. You can find more information about affiliate links here.

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