Fabia Oxygen sensor problem?

[MathiasS]

Hi all,

I have a problem with my Fabia 2001, 74kW/101hp, engine code AUB.

This is what I get from VAG-COM:

Saturday,25,November,2006,17:35:25

VAG-COM Version: Release 607.3-UD

Control Module Part Number: 036 906 034 BK

Component and/or Version: MARELLI 4LV 3700

Software Coding: 00031

Work Shop Code: WSC 13765

Additional Info: TMBPD26Y413164010 SKZ7Z0Y0678456

3 Faults Found:

17589 - Linear O2 Sensor; Reference Voltage: Open Circuit

P1181 - 35-10 - - - Intermittent

17587 - Linear O2 Sensor; Pump Current: Short to Ground

P1179 - 35-10 - - - Intermittent

17604 - Oxygen (Lambda) Sensor Heater Circuit: B1 S1: Electrical Malfunction

P1196 - 35-10 - - - Intermittent

Readiness: 0000 0000

From a cold start, the engine is completely without power and sometimes has trouble keeping a steady idle rpm. Once reached normal temperatures it runs better but of course still not ok.

If I clear the codes they will come back after a few minutes/seconds of driving. With the DTCs cleared the car feels and runs ok.

I first thought this was an electrical problem because before, the car could run for many days before the DTC reappeared. Now the DTCs will be set almost immediately as described above.

If I check measuring block 31 (I think it was) two lambda factors are displayed, numbers vary from 0,9 to 1,2 (acc vs deacceleration). This makes me wonder if its really the oxygen sensor that is the problem? If I can read the output from the lambda sensor, the the ECU should be able to do that as well.....

Is there any way to tell which sensor generates the first two codes?

Just changing the first sensor might be the obvious thing to do, but its quite expensive (220Euros here in Sweden) so I would like to be sure that will really fix the problem.

What do you think? What else should I check before changing the sensor (S1B1)?

Thanks in advance.

Br,

Mathias

[VRStu]

I would say that it's more likely a wiring fault just looking at the codes.

[MathiasS]

I would say that it's more likely a wiring fault just looking at the codes.

Thanks for your input.

Yes that might be it. I have checked the connector attached to the sensor-cable but that looked fine. I will check the wires closer to the sensor, maybe its been too hot there or something.

Any additional input is more than welcome.

Br,

MathiasS

[TeflonTom]

first question.... does your car have 2 lambda probes??

my guess is that the wiring plug for the lambda probe has been plugged in the wrong way round, they have 4 pins, and although the should only fit one way, if you force them, you can plug them in the wrong way round...

the woring plug for the lambda probe is mounted next to the one of the knock sensor, and it's under the thermostat housing on the right hand end of the cylinder head, they are kind-of pushed into this little steel right angled bracket and they are a right sod to remove.... possible cause could be careless refitting after a sensor change

[MathiasS]

first question.... does your car have 2 lambda probes??

my guess is that the wiring plug for the lambda probe has been plugged in the wrong way round, they have 4 pins, and although the should only fit one way, if you force them, you can plug them in the wrong way round...

the woring plug for the lambda probe is mounted next to the one of the knock sensor, and it's under the thermostat housing on the right hand end of the cylinder head, they are kind-of pushed into this little steel right angled bracket and they are a right sod to remove.... possible cause could be careless refitting after a sensor change

Yes, it should have two probes.

Since I was in the car, driving it, when this error first occured, this cant be the result of conectors plugged in the wrong way. But before buying a new sensor, I will for sure check the wiring according to your post here. As far as I can tell from the cars documentation, no sensors has been changed up to now.

Br,

MathiasS

[TeflonTom]

the sensor might not have been changed, but it is often neceassary to unplug stuff to get access to other components

[MathiasS]

the sensor might not have been changed, but it is often neceassary to unplug stuff to get access to other components

Thats a good point. Will check it all as soon as I can remove some crap from the garage this weekend....

[MathiasS]

I have now checked the wiring and it looks fine. Everything is plugged in correctly and there are no visible trace of over heated cables.

What I have also noticed during a test run is that the car seems to run normally if I clear the codes after the engine is warm. I drove the car for 15-20 minutes without problems, no DTCs.

I also monitored all values related to the oxygen sensor during a cold start of the car - the voltage reading is way out of specification and I guess that is what causes the car to run like crap.

I believe all this indicates that the pre heating of the sensor does not work properly?

What would be the best way to determine if the pre heating circuits works as they should?

[Chris_55]

Similar proble here the info in it may be of help.

http://www.briskoda.net/forums/diagnostics-vag-com/help-o2-sensor-oxygen-sensor-fault-codes/67644/

"17604 - Oxygen (Lambda) Sensor Heater Circuit: B1 S1: Electrical Malfunction"

B1 = Bank 1 (there is only 1 bank on a Fabia)

S1 = Sensor 1 (The one nearest the engine)

If you had a code for S2 it would be for Sensor 2 (The one after the CAT)

[MathiasS]

Thanks for the link.

I think I will sort out the wiring for the sensor and then manyally measure the resistance of the heater circuit.

[MathiasS]

A short update to close this thread:

The car has been parked for a while because we have not had any use for it. Now it was time to start using it again and also time to sort out this sensor problem once and for all.

I decided to replace the oxygen sensor. 180Euro for the part, 20minutes of work, clear DTCs with VAG-com and the car was once again running as it should.

Thanks all for the input in this thread!

[Tech1e]

Sorry i didnt spot this thread earlier :(

Usually when a lambda probe flags up a heater circuit fault it is the probe itself at fault.

[MathiasS]

Sorry i didnt spot this thread earlier :(

Usually when a lambda probe flags up a heater circuit fault it is the probe itself at fault.

I believe that a lot of things was wrong with this probe.....

Btw, I saved my self 50Euros from buying the probe (NGK) from someone else than directly from Skoda/VW.