Hi there

I’m new to this forum. Looking for some help. 

I'm working on this Skoda Fabia 1.4 2004 Auto 16v engine code BBY, having issue with O2 sensor. MIL is on. with Obd connected shows the following codes;

p0135 (Heated oxygen sensor (HO2S) 1, bank 1, heater control circuit malfunction),

p1178, p1178p, ( Heated oxy sensor 1 bank 1 heater current open circuit)

 

so I replaced the sensor with a new  same NTK one and cleared faults with a basic obd2 tool and now getting

 

1- p1180 (Linear Oxygen Sensor Pump Current Short To Positive)

 

2- p1178, p1178p, ( Heated oxy sensor 1 bank 1 heater current open circuit)

 

3- P0030, (Heated oxygen sensor (HO2S) 1, bank 1, heater control -circuit malfunction)

 

4- P0135 ( Heated oxygen sensor (HO2S) 1, bank 1, heater control circuit malfunction)

I've read on a different forum that it could be a broken/ cracked wire from O2 sensor to ECU, so i decided to give it a go and check the continuity of the wires going from O2 6wire plug to ECU.
 

For that i had to take the battery and casing out. the o2 sensor connector plug is marked from 1-6 from different color wires. I've checked the continuity on all wires and they end up in the big plug connecting to ECU. Only issue here is when I check continuity for Wire # 2 on O2 connector plug,  which i suppose and remember is the live wire with ignition ON, it shows continuity with two different pins on the ECU connector and also shows continuity witht the ground wire (brown wire) , going from the same loom to the negative battery pole. 

 

i have checked the wiring loom pretty much all the way from O2 sensor plug to Ecu and there does not seem to be any crack or break in any of the wires. 

Now ! I'm not an electrician , just know the very basics about wirings. So I'm a bit confused whether its normal that the live wire #2 at O2 connector plug  is connected to two different  pins at ECU and also to the wire going to battery negative pole or

is it  that there should only be one ECU pin for each of 6 wires going in to the ECU from O2 Sensor Connector Plug and in this case of wires being fused together somewhere and being connected to more then one pins at ECU and i need to dig further?

anyone with any help ?

much appreciated.

thanks

ash

Which ECU pin numbers are you seeing connectivity with?

Disconnecting the other  oxygen sensor may remove one pathway, as there'll be a connection through its heater (powered from the same fuse, No. 9) to ECU pin 63.

Wiring diagram also shows a resistor between oxygen sensor 1's connector pins 2 and 4, but it's not clear whether that's on the loom half of the connection or the sensor half, I suspect it may be the latter? 

Edited 26 August, 20214 yr by Wino

Hello wino 

First of all thanks a lot for sparing time and quickly replying to my post. Do appreciate. 
 

Yes you are right, the second sensor B1 S2 never crossed me mind. Now I’ve realised that there could be connections through there as well so I decided to check the connection again thoroughly and managed to draw two tables showing connections in different pins. I’m attaching to pictures. 
 

i have been able to disconnect the B1 S2 because I’m trying to in do the central console to get access to the plug. Will do that later on. 
 

please have a look at the charts and suggest if these connections are in line with diagram or there seems to be some unusual connectivity causing a short circuit etc. 
 

I have tried to draw as clean as I could but if you have difficulty reading then please excuse my writing skills. 
 

thanks. 
 

 

 

I can read it fine, because it's beautifully clear!

Will check over everything this evening, comparing with my car for anything that seems surprising. 

Edited 26 August, 20214 yr by Wino

Ok thank you

All seems OK to to me, with the following observations:

I think maybe you labelled the two tables wrongly, the first one is with fuse out, the second with fuse in?  It makes sense that way, because with fuse in and ignition on, there are pathways for connectivity 'backwards' through the fuse and battery to the power rails.  These connections don't matter. It does prove that the connection from oxygen sensor connector pin 2 to fuse 9 is intact though.

 

Your connector pin numbering for the ECU connector seems wrong with the 12345 section mirrored with respect to the remaining pins, it should look like this:

 

Just by correcting that, everything seems OK, because the only connection that looks wrong is Oxygen sensor connector pin 1 to ECU pin 2, which should instead be ECU pin 5. This comes out OK once you correct your numbering on your drawing.

 

 

Hi 

yes you are absolutely right. I don’t know what I was thinking when drawing it really. 
 

the pins are and should be as you described them and also fuse thing too. 
 

 Pin 2 have lots of connections and if all is normal then I think I should try a different O2 sensor then. You racon 

but before I replaced the o2 s1 B1  the MIL was intermittent but now it’s constant. 
another thing happened yesterday when I put all back and started the car with fuse 9 out, the MIL light got cleared but after about 2 minutes came back, I turned off the car and put the fuse back started the car and Mil came immediately.

 
I checked code and the Code for the O2 B1 s2 also came for a heater circuit problem. How can it just blow the sensor heater? I don’t know. 
 

To me This suggest there some eclectic circuits may be playing up somehow. 
 

I think I can get to the cause of p1180

 

1- p1180 (Linear Oxygen Sensor Pump Current Short To Positive)

 

it might help putting things right. 
 

But I read somewhere that the ECU has a Skoda recall for updation, will have to ask Skoda for that. 
 

I’m rechecking the sponsors for resistance and voltage. 
the resistance between pin 1 and pin 2 is 3.8 ohm almost same for the old and new sensors. 
 

 do you know what voltage / current should I  get on each sensor adopter pins with all attached and car running? 

Thanks again for your Time and attention. 

AbuHSN 

 

Fuse 9 powers the heaters in both sensor 1 and sensor 2, so removing the fuse should generate faults relating to both heaters.

Pin 2 of sensor 1 (and pin 1 of sensor 2) should have 12V with ignition on.  The control of the heating is done by the ECU earthing pin 1 (pin 2 for sensor 2) for varying proportions of time (pulse width modulation). 

 

 

Could you re-check the connectivity of pin 2 of sensor 1 connector?

I think you should see a few Ohms from that pin to ECU connector pin 63 when sensor 2 is connected normally.  You are effectively measuring the resistance of the heater inside sensor 2 by measuring this path, as well as confirming the connections in and out of that heater.

 

 

Ok great 

Thanks wino

 

I’ll check this afternoon and confirm. 

hello wino 

I’ve checked bt pins 2 and 63 and there is resistance and it’s 5.2ohm. 

 

I’ve put the things back checked the codes and behold there is another code now P0106. 

any idea what that could be?

 

Thanks   

Check carefully the joints of the hard plastic sections of the brake servo vacuum hose.  

They split and leak air, making the MAP sensor give readings to the engine ECU that confuse the poor thing.

 

Ok 

Will check in the morning and update. 
 

thanks for your reply do appreciate. 

Hello wino 

update…

I’ve put everything back, checked all the vacuum hoses no crack or demage.  
MIL was on at first but for some strange reason it went after about 10 mins of drive. 
Started the car this morning and drove for a while and strangely the MIL light went off. 

 

could it be the battery voltage as some people have mentioned in few forums? 
I don’t know. 
 

But 

thanks a lot for your help and advice. 
do appreciate. 
 

AbuHSN 

1 hour ago, AbuHsn said:

could it be the battery voltage as some people have mentioned in few forums? 

Yes, possibly.

 

You're welcome.