The engine warning light came on today, so a quick OBD2 scan tonight revealed code P1178 stored on there. This code seems a bit ambiguous online, i.e. there isn't much there, but the few bits I've read is that it may be related to the pre-cat Lambda sensor (or oxygen sensor LOL); given new sensors are a silly price, I thought I'd ask here if anyone knows what this code means on a Polo 9N, and what 'typical' values for the oxygen sensor? Mine are here:

Code read with engine warning light still on:

Sensor voltage & fuel trim with code still there & engine warning light still on:

Sensor voltage & fuel trim with code cleared, engine warning light off, after I had a jiggle of the wires coming from the pre-cat O2 sensor to the connector block:

I should add, the car is a 1.4 16v 75bhp, BBY engine code, 2003 model.

Any ideas? Thanks in advance.

Edited 7 March, 201313 yr by Paddy2bsure

Code is manufacturer specific. So for all VAG cars it would be the same.

This instance its a linear lambda error. And points to the pre cat sensor needing to be replaced.

P1178 = VAG code 17586 Heated oxy sensor 1 bank 1 (before cat in the manifold) heater current open circuit, causes:- Wiring open circuit or sensor

Check the resistance between pins 1 & 2 of the sensor should be around 2 ~ 10 ohms and on the car side of the connector 12v on pin 2

Edited 7 March, 201313 yr by nige8021

I changed the O2 sensor today, replacement came from ECP for £120ish; I put some new plugs & air filter on too, and no more P1178 code. However I have got a cylinder 1 misfire & the thing is running like a bag of spanners. It's never ending.

The question is, is the misfire caused just by a badly seated coil pack, or could it be O2 sensor related (unlikely IMO).

I've been thinking about selling the car lately - do you think it knows?!

I changed the O2 sensor today, replacement came from ECP for £120ish; I put some new plugs & air filter on too, and no more P1178 code. However I have got a cylinder 1 misfire & the thing is running like a bag of spanners. It's never ending.

The question is, is the misfire caused just by a badly seated coil pack, or could it be O2 sensor related (unlikely IMO).

I've been thinking about selling the car lately - do you think it knows?!

did you check the plugs before you installed them?

as they might have been damaged or the gap might be incorrect or grounded explaining the misfire.

i'm assuming your polo has the pencil type coil packs.

if the coil pack isn't seated right it might not have a good connection to the spark plug so make sure they're right.

i take it you've talked about selling it in front of the polo so now it has decided to make it's self unsellable.

Yup, it's in self deestruct mode LOL It's been a really great car in the last few years, but trust it to throw a hissy fit now, with tax just done, MOT due. PITA!!!!

Plan tomorrow is to swap the coil packs around, and see if the fault stays with the cylinder/plug or the coil pack.

Took all the coil packs out, and swapped them round; I took the plugs out out of curiosity (all fouled as it was running on 3 cylinders); put it all back together & now it's running like a watch. I don't think one of the coil packs was shoved down enough, so wasn't making proper contact with the plug tip. All good now though - phew.

Some new tyres going on later this week, MOT at the weekend... and then it'll be for sale - probably

This was today's doagnostics reading - so I guess these are the values for a healthy Lambda sensor!

Edited 10 March, 201313 yr by Paddy2bsure