HI,

 

My 2015 Skoda Fabia mk3  Combi 1.0 MPI fuel consumption is trough the roof (from around 5-6 l/100 km to 10 l/100 km)  and I get a P2096 OBD2 default : POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 1

 

I get the rear lambda sensor is really measuring too much oxygen in the post catalyst exhaust gases or the rear lambda sensor is defective.

 

Cannot find any vaccum leak in the exhaust manifold from a visual inspection, and to be honest I don't have access to a smoke machine.

Don't have access to VCDS nor a simple or advanced OBD scanner yet.

I have access to a multimeter  but no access to an oscilloscope !

 

The question is : should I go for a front or a rear lambda sensor change ? 

 

Thanks !

 

Hi, welcome.

 

15 hours ago, Star7 said:

I have access to a multimeter 

Then why not use it to test the sensors, plenty of videos and information about, just one example. -  https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/

2 hours ago, nta16 said:

Then why not use it to test the sensors

Measuring 7 ohms for the heating resistor wires on both sensors with open wires

Erratic/inconsistent 8- 110 mV 🥴 for the sensors wires even going 2000 rpm.

 

Measurements are quite complicated and unreliable.

I get the resistor from both sensors is good but the sensoring part is a shot in the dark for both sensors.

 

I cannot believe I have both sensors gone mad at the same time ? Or is it possible ?

 

Statistically does the rear sensor is more leading to faults than the forward one ?

 

Thanks !

 

 

Welcome and sorry no idea as to your question.

 

Can you tell us how many km has the car done and are there nice condition spark plugs fitted with the correct gap and a nice clean air filter fitted? 

51 minutes ago, Rooted said:

Can you tell us how many km has the car done and are there nice condition spark plugs fitted with the correct gap and a nice clean air filter fitted? 

Sure !

 

77000 km. Urban usage.

Spark plugs were changed 2 years ago at 60000 km.

Clean air filter fitted.

 

The spark plugs were changed for the "advanced inspection" ( as per Skoda workshop manual) of the car 2 years ago at 60000 km because there was also an excessive fuel consumption and I guess it was required by the "advanced inspection".

 

I could change again the spark plugs but I find quite surprising to do so after only 17000 km since the last change. I may have used some unleaded 95-E10 instead of unleaded 95-E5. Could it be the reason my spark plugs are not functioning well ? I guess I should have other defaults than a P2096 OBD2 alert from the ECU in case of a misfiring ?

 

Thanks.

 

 

Just for info, you may already know and have done but in case not.

 

"In order to achieve flawless measuring results, the engine should be kept at a speed of approx. 2,500 rpm. This ensures that the operating temperature of the probe is reached, even in systems with an unheated lambda sensor. If the exhaust gas temperature is not sufficient in idle mode, there is a risk that the unheated probe cools down and a signal is no longer generated." - https://www.hella.com/techworld/uk/Technical/Sensors-and-actuators/Test-lambda-sensor-4379/#

 

 

"Narrowband sensors (zirconia and titania), especially pre-catalytic converter, are tough to test with a multimeter.  Multimeters do not respond fast enough to catch a narrowband sensor’s rapidly changing output."

"3. Connect the multimeter to the heater’s power wires or contacts.  Back-probes are the best tool for this. If you do not have access to back-probes, it may be easiest to connect the multimeter to the power lines by disconnecting the oxygen sensor from its harness, and connecting the multimeter to the connector.  You should read the engine service manual to learn what you can and cannot do here." - https://gtc.ca/blog/testing-oxygen-sensors/