Good morning all and well I hope.

On the 02, polo 1.2.

The pre-cat sensor has thrown a fault, just the week before I had changed the front downpipe because the flexible joint had given up!

 

So, had a go at removing it yesterday and I have some questions.

1. What is the little bit below the coupling and what does it do. It is now in bits and I just wondered. It looks like a small fuse perhaps? Picture attached

2. The sensor is well stuck in the manifold. I can turni it a bit and then it gets too tight and I am reluctant to over force it. Any suggestions on safe removal please? Should I WD, get a bigger wrench etc etc>?

3. It is an expensive part to replace. Thoughts on a salvage sensor or false economy?

 

Kind regards and many thanks

Phil

 

I think the bit in the connector is a bespoke tuning resistor to bring the sensor into a standard operating range.

 

Penetrating fluid and lots of small back and forth spanner work should bring it out, gradually. Probably baked on carbon on the threads exposed to exhaust flow.

 

I may well have a good spare I could offer at a bargain price, will try to check this evening.

OK and thankyou for the quick and helpful reply. If you have one to sell I would be delighted. I'll wait for your update

Kind regards

Phil

 

Did it just fall off or did you " whack " it off?

You could just re-solder the calibrating resistor back onto the sensor...

 

John ;-)

A good question. I was tempted more than once to just hit the whole thing. 

Actually in trying to get the connector off of the bracket the plastic surround came off and the resistor dropped to the floor. I don't think it was originally soldered, just a touch contact. The aging and now cracked plastic is beyond use now!

Anyway, the sensor threw a fault before this, so expecting to change the whole thing anyway. The resistor bit is certainly beyond easy repair.

Any thoughts on how hard the sensor should be to unscrew from the manifold?

 

Kind regards

Phil

 

Looking at the photos ..seems like the resistor still has the marks as to where the "feet" were soldered before , and the "feet" on the body look good , maybe this was your original fault after wrestling with  the downpipe?

 

If it was me I'd fire the soldering iron up...

 

John

mmmmm was just thinking about that too. Soldering iron - not a big job and might solve the problem. 

Extensive use of the old rattle gun to get the old pipe off, so it is conceivable.

Will let you know how I get on.

Many thanks

Phil

 

This is what that area looks like on an undamaged one, soldered joints as very well observed by John.

 

 

I think this is probably a good spare but the part numbering is a bit obscured by rust, might respond to a clean-up should it be useful to investigate further.  Think I might even have another somewhere..

 

 

 " Anyway, the sensor threw a fault before this "  , it is only recently ( relatively speaking ) that they have been using solder with no lead content , causing many problems of this sort , dry joints etc. etc....

 

John

OK - took the mighty soldering iron to it and have stuck it back on. No fault yet but only 25 miles on!

The feet did not look very soldery so maybe no surprise that it had dropped off, but tinned the feet and the resistor and it seemed to take well. I did this before the comment about lead free. I used leaded solder and as said it seemed to flow fine. My eyes are not what they used to be though!

Fingers crossed and it is off for an MOT next week!

Thankyou all for your comments and help on this one. It's great having people to ask.

Kind regards

Phil

 

 

Good work by you and John here; sounds promising. Was there a clip-on cover over the resistor weatherproofing it? There should be.

 

I did manage to read the part number from the one I photographed above; it appears to be a Bosch 0 258 007 357 which does seem to be the correct one.  It looks far from new, but the 'business end' looks a suitable colour rather than a sooty, oily mess, so probably works.  PM me about it if you do get a re-occurrence of fault code. 👍

 

Edited 24 February, 20224 yr by Pete1
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Half a clip! One half broke off. It went on OK though and is past the seal so I am hoping OK.

The 'frame' inside is in small pieces so this has gone.

Problems brewing do you think?

Phil

 

 

 

4 minutes ago, Phil H said:

Half a clip! One half broke off. It went on OK though and is past the seal so I am hoping OK.

The 'frame' inside is in small pieces so this has gone.

Problems brewing do you think?

Phil

 

 

 

 

Not necessarily. As long as you have the little engine undercover fitted, that location shouldn't see a lot of splashed water. Maybe just check it now and then to see that the cover hasn't fallen away, if the sensor carries on behaving. 

Good point.

The undercover has not been there since the car was bought 5 years ago actually. It's my daughter's car and she is not always at home, so will hatch a plan.

The car runs fine with the sensor not working, and it is only the MOT folk who want to see the yellow light off on the dashboard, so I think if it breaks again there will be time to organise a replacement and fit it when she is next home.

Kind regards

Phil

 

 

I can probably fix that for you, at the risk of antagonising the tester.

The MOT test manual suggests that the car is too old for them to care about the MIL:

 

 

Wow and never knew that. Very handy as my car is a 96 1.4. No lights at the moment and MOT also next week!

Phil

 

2 hours ago, Phil H said:

Wow and never knew that. Very handy as my car is a 96 1.4. No lights at the moment and MOT also next week!

Phil

 

There is no MIL/EML on the 96 speedo so no need to worry