Polo 9N AWY 'check engine' light on

Akagi · 26 Oct 2014 at 04:28

Blackhawk47 said:
When is the next thread?

Today...

I will be getting my mechanic to have a look, but obviously it is Sunday tomorrow, so this is more of an "in the mean time, what can I try" thread.

My car is a 2002 VW Polo 9N 1.2 6V AWY with 138K on the clock.

I was driving home earlier today and the 'check engine' light came on.

There are no strange sounds coming from the engine, the engine idles smoothly, the engine pulls fine through all gears, there is no "lumpiness" and no misfires throughout the entire rev range. I have checked all fluids and all seem fine, I have checked all hoses and plugs as much as I could at the side of the road (just visual checks for obvious splits or loose hoses/disconnected plugs etc) and there don't appear to be any obvious issues.

I have tried various methods which are supposed to clear lights/errors or reset the ECU (I don't know how many [if any] of these are genuine methods but I tried these regardless):

- Pressing in trip button for 2 seconds and turning to the right
- Pressing in trip button for 2 seconds with key turned to lights position, and turning to the right
- Pressing in trip button, holding, turning ignition to lights position, holding, turning ignition off, removing keys, and releasing button
- Disconnecting negative terminal for 15 minutes and re-connecting, then starting engine
- Disconnecting negative terminal for 3 minutes, then re-connecting, then turning ignition to lights position, waiting 3 minutes, turning ignition off, removing key, putting key back in, then starting engine

Points to note:

- Engine had a full tank of petrol when this happened, it was cheap supermarket petrol though (Tesco 95) and I usually use Momentum/Ultimate/Super or sometimes Esso 95
- Radiator fan is faulty and non-working (blows fuses) but it has been like this for 2 weeks/500 miles, I have been careful with the engine, and never seen it go above 90 degrees. (replacement fan is in the post)
- The car was involved in an accident a few weeks ago, but it has been fine from after the repairs up until now (again, 2 weeks/500 miles) and it was fine before (never had the light come on)

The only engine component which needed replacing following this incident was the radiator.

If anyone could shed any light on the subject or give me things to try, it would be much appreciated!

I do not have access to any diagnostic equipment.

Finally, would you advise against driving the car while the check engine light is on persistently, even if there are no obvious issues?

Kind regards!

Akagi · 26 Oct 2014 at 12:45

Yes I normally put Momentum in a 1.2 6V because at something like £2 more per tank, it seems pointless not to. Tesco is the only local petrol station which is open 24hrs, and if the choice is Momentum at 127p or Tesco 95 at 124p, I'll use Momentum. The pump had no Momentum this time though.

Yes it is another Acme car falling to bits thread...

I'll get the codes read, was just hoping someone would know something obvious to check which I've missed.

I've been advised (without checking codes yet, I'll get on that right away) that it is most probably a faulty sensor, and it could even be something as simple as a "bad" bit of fuel being dragged through the system.

The guys over on Pistonheads and ClubPolo have basically said that it should be fine to drive until the codes are read if there are no obvious issues.

Akagi · 26 Oct 2014 at 13:14

Lets hope that doesn't happen... I mean, it definitely isn't misfiring.

I hope it is something simple too... I know you are probably all fed up with the Polo threads, but I'm fed up with owning this damn car at this point... All I wanted to do was fix it and run it until the new year when I can wave bye bye to it. Apparently that is too much to ask even after replacing almost EVERYTHING.

Seriously, I need to get this thing re-registered. Not much of it is 12 years old anymore.

Akagi · 26 Oct 2014 at 14:47

Think I may have found what the issue is, the cable for the lambda sensor looks like it got pinched in the accident and the insulation is torn and ragged and there is bare wire showing, so I guess it might have shorted on something.

Akagi · 26 Oct 2014 at 15:22

Will give it a go perhaps.

Akagi · 28 Oct 2014 at 12:34

Have driven another 50 miles or so since the light came on and everything still seems absolutely fine.

What cheap OBD reader would you recommend? I would just get a VAGCOM cable, but I don't actually have a laptop.

Akagi · 28 Oct 2014 at 13:00

They are like £5?

Akagi · 28 Oct 2014 at 13:15

Have ordered a reader at the recommendation of someone from the Polo forums. It should be here tomorrow.

£16.99 including upgraded delivery.

Akagi · 28 Oct 2014 at 14:47

acemastr said:
Super unleaded... you crack me up.

Really? What is the point in *not* using better quality fuel when it is only 3P more per litre? :confused:

It surely has to be marginally better for the fuel delivery & injection components, it costs about the same amount per mile because I get a few more miles out of a tank*, and to me, the engine feels slightly more plucky with less flat spots.

*I tested something like 8 tanks of regular 95 and 8 tanks of Momentum 99 doing the same runs to and from the same places and I got a consistant 2 - 3 MPG average advantage over 95 when using 99.

Akagi · 28 Oct 2014 at 14:53

I tested something like 8 tanks of regular 95 and 8 tanks of Momentum 99 doing the same runs to and from the same places and I got a consistant 2 - 3 MPG average advantage over 95 when using 99.

I have all the figures noted down somewhere, will look for them when I get home if you want.

I was surprised by it as well. It might be something to do with the weird low power triple cylinder short-stroke engine in the Polo? Something knock sensor related? I don't know...

Akagi · 28 Oct 2014 at 15:28

Seems a little odd that each tank was consistently better... I don't know what exactly I would subconsciously change about my driving style if I know I have better fuel in the tank?

Akagi · 28 Oct 2014 at 15:47

Janesy B said:
Depends how many hedgerows you ended up in I guess?

THAT WAS ONE TIME JANESY B! ONE TIME!

Unfortunately it did have a tree in it.

Akagi · 28 Oct 2014 at 16:41

ElliorR said:
Penny?

I'm sorry...?

Akagi · 28 Oct 2014 at 16:48

Hyburnate said:
It'll never be forgotten, I have the picture saved on my phone from the time you sent me it after you'd done it

"I dun goofed..."

Akagi · 28 Oct 2014 at 17:38

[TW]Fox;27124100 said:
Your car has illuminated a light telling you that there is some sort of engine fault. You don't yet know what this fault is, so your idea is just to... keep driving the car? Really?

This made me chuckle.

Well the folks over at ClubPolo and Pistonheads (including a VAG techie) said that it would "probably" be fine to drive if there are no noticeable symptoms, because it almost certainly means that it is just a sensor.

To be perfectly honest Fox, I couldn't care less at the moment... OBD reader is coming tomorrow so I'll soon know where the problem lies, and in the mean time, I'll continue to drive it unless it sounds or feels like it is about to blow up. :rolleyes:

I am pretty sure that it is just the post-cat lambda anyway. It makes sense because:
A.) they tend to go after about 10 years, it has been 12.
B.) there are no noticable symptoms whatsoever
C.) the cable for the sensor is in terrible condition and looks like it got pinched in the accident, with the insulation shredded and some of the wire strands severed

If it does blow up or break irreversibly, then the risk of driving it didn't pay off, and I'll look like a ****, and thats that.

Akagi · 28 Oct 2014 at 18:48

Akagi · 28 Oct 2014 at 22:08

So it would be better for me to use Shell or Esso 95 than Tesco 99 then basically?

I use Momentum cos I fill up at stupid hours when Tesco is the only place I can buy fuel, and when I'm there I can choose between 99 or 95 so I go for the 99 in the hope that its better quality than the 95.

Also I'm the 6th or 7th owner, not the 14th lol.

Akagi · 29 Oct 2014 at 00:23

Maybe...

Akagi · 29 Oct 2014 at 18:20

There are other things he will need to look at as well, I'll get a list later.

Akagi · 29 Oct 2014 at 19:30

Right so, the OBD reader returned three fault codes:

16804
17978
16556

The first one, 16804 isn't in the accompanying booklet, but Google suggests that it is "Catalyst System; Bank 1: Efficiency Below Threshold"
The second one, 17978 isn't in the accompanying booklet, but Google suggests that it is "Engine Start Blocked By Immobiliser"
The third one, 16556 is in the accompanying booklet, and it is "Fuel Trim: System Too Rich: Bank 1"

I am not concerned about the second one regarding the immobiliser, as the engine starts and runs fine, there have been no issues with the immobiliser, and I think it may have happened when I had a third party key programmed for the car.

So looking at the first and third ones then:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold
16556 - Fuel Trim: System Too Rich: Bank 1

Any ideas? I'm guessing that 16804 is that lambda sensor, or could it be the cat? Is 16556 likely to be related and/or possibly the cause of 16804?

Should I clear them and see if they come back, first off?