How To Change Oxygen Sensors in 2002 Mercedes C240 Sedan?

oxygen sensors ( O2S) are located after the cat converter/s
heated oxygen sensors (HO2S) are located in the exhaust manifold/s before the cat converters
so on a 4cyl/in line 6 cyl engine --1 of each
on a v6/v8 --2 of each

This is a fairly common problem with naturally-aspirated engines as they age, because the oxygen sensors become contaminated and do not operate as effectively, plus the idle air controls become sluggish in their operation and fail to adjust quickly enough. If the CHECK ENGINE light is on, check the codes, and most likely you will find that one or more of the oxygen sensors are at fault.

Try starting the car while holding the throttle at 1/3 to 1/2 until it starts. If it starts more easily that way, do that each time you start the car when it's warm. Replacing the oxygen sensors and the idle air control will solve the problem but part-throttle starting will save time and money in the meantime if the trick works.

P0429 Description The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2 sensor).



A three way catalyst converter (Manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.



When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed.
Possible causes - Catalyst Heater Control harness is open or shorted
- Catalyst Heater Control circuit poor electrical connection
- Faulty Powertrain Control Module

Locate the two oxygen sensors on either side of the Sonata's catalytic converter on the exhaust manifold. The Sonata's oxygen sensor is gold and shaped liked a spark plug.

2 Remove the Sonata's wiring harness from the end of the two oxygen sensors using your fingers. Do not damage the end of Sonata's wiring harness.

3 Remove the two oxygen sensors from the Sonata's manifold using the oxygen sensor wrench.

4 Apply the anti-seize compound to the threads of the Sonata's two new oxygen sensors.

5 Install the two new oxygen sensors to the Sonata's manifold using the oxygen sensor wrench. Re-attach the wiring harness to the two new oxygen sensors using your fingers.

to make you clear where does the oxygen sensors where is........... some have four, three or two, all O2 SENSORS ARE LOCATED AT EXHAUST PIPE. before and after catalytic converter,

code p0335

Remove the Oxygen Sensor
1. Step 1 Start the engine and let it idle for four minutes to raise the exhaust system temperature. This will make removal of the oxygen sensor much easier and prevent damage to threads on the exhaust pipe.
   
2. Step 2 Turn off the engine.
   
3. Step 3 Detach the ground battery cable using a wrench.
   
4. Step 4 Locate the oxygen sensor or sensors you need to replace. The sensors are threaded into the exhaust pipes before and after the catalytic converter. The oxygen sensor has a cylindrical body and the approximate size of a spark plug.
   
5. Step 5 Raise the front of your vehicle using a floor jack and support it on two jack stands. This will help you gain access to the sensor or sensors if necessary. If you need to work under the vehicle, wear safety goggles.
   
6. Step 6 Unplug the sensor electrical connector.
   
7. Step 7 Unscrew the oxygen sensor using a box-end wrench or a ratchet and oxygen sensor socket.
   
8. Step 8 Remove the sensor or sensors from the vehicle.
   
Install the New Oxygen Sensor
9. Step 1 Apply a light coat of electrically conductive anti-seize compound to the threads of the new oxygen sensor.
   
10. Step 2 Thread the oxygen sensor into the exhaust pipe by hand first.
    
11. Step 3 Finish tightening the sensor using the box-end wrench or ratchet and oxygen sensor socket.
    
12. Step 4 Plug the sensor electrical connector.
    
13. Step 5 Lower the vehicle.
    
14. Step 6 Attach the ground, battery cable using the wren
    

all oxygen sensors are located on the exhaust pipes. depending on the specific configuration, there can be 2- 4 sensors. always will be a set before the catalytic converter and a set after the cat. converter.

try the fuel pump relay or the fuel pump

two at the front on the exhaust cat and two on the rear, and yes if there tight