Ok guys since I bought my Octavia vRS last october, I have had a re-ocuring fault code pop up.

Namely:

17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)

P1297 - 35-10 - - - Intermittent

To try and fix this, I have replaced the dump valve, and checked around for leaks, but not found any obvious issue's, other than a broke S pipe on the breather system, but I have since fixed that problem.

The car doesn't go into limp mode, when it throws the code, and it hasn't thrown a cel for it either.

I have recently fitted a front mount intercooler (Pro Alloy) and it has thrown the fault again since fitting that, so I can assume there is definately no leaks after the pancake pipe.

However since I fitted my turbo back exhaust last week, the car hasn't been running right.

Pretty much as soon as the 3" downpipe and catback system were fitted I noticed at low rpm there was a flat spot that wasn't there with the standard system, but as it's been bloody cold since I fitted the exhaust and snowing etc, I wasn't 100% sure if it was the weather causing the flat spot.

Well this morning on the way to taking my mrs to the hospital the engine management light came on.

So I have just checked with vagcom and again the above 17705 code is back, but also:

16804 - Catalyst System: Bank 1: Efficiency Below Threshold

P0420 - 35-00 - -

Now I know that it is normal for a cell to be thrown when you fit a downpipe / decat, but I thought it was the rear lambda sensor that caused the problem, and not the front (I am assuming Bank1 is the front sensor) ?

In vagcom I found the measuring block that says front 02 should be 111 at idle and rear should be 110 at itle. Mine were both switching from 011 - 111 on the front and 010 - 110 on the rear.

Also would the front sensor cause the above flat spot at low rpm ?

Edited 22 January, 201313 yr by Cossie1

anyone ?

Have you already seen this? -

http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056

Have you already seen this? -

http://wiki.ross-tec...04/P0420/001056

Yeh I did read that, thanks

But i'm still not sure, if the fault I have is because of the decat as I would expect it to be rear 02 (or bank2) sensor to be throwing the fault.

There is no leak at the downpipe / decat flange (infact no leak anywhere afaik).

Hi, That was the exact code I was getting since my decat. It's the difference between the 2 sensors so might just be a strange name for it.

I was talking to a mapper today and he actually mentioned something about the pressure drop error code being a software issue and not necessarily a physical fault. Don't really know exactly what he meant but worth looking into maybe if you are sure that there are no leaks.

Hi, That was the exact code I was getting since my decat. It's the difference between the 2 sensors so might just be a strange name for it.

I was talking to a mapper today and he actually mentioned something about the pressure drop error code being a software issue and not necessarily a physical fault. Don't really know exactly what he meant but worth looking into maybe if you are sure that there are no leaks.

Lovely, thats the exact info I needed thanks

17705 can be a nightmare to solve. 99% of the time it's down to leaking pipework, DV seal or the throttle body being gunked up. However I had a problem with 17705 on mkiv Golf a few years ago, which I eventually pinned down to the custom code map that had recently been loaded in.The Tuner insisted the map was fine & that I must have a boost leak somewhere, & I replaced pretty much all the boost & vacuum pipework, plus a Forge007p, but couldn't stop the problem. Eventually I stumbled on a thread on Canadian forum where someone had the same problem & his tuner had found it was caused by an incorrect value in the software. I'd given up getting anywhere with the Tuner who'd put my map in & In desperation I got the Revo trial loaded, problem solved immediately no more 17705. I got Revo stage 1 a week or two later, & I never saw 17705 again.

17705 can be a nightmare to solve. 99% of the time it's down to leaking pipework, DV seal or the throttle body being gunked up. However I had a problem with 17705 on mkiv Golf a few years ago, which I eventually pinned down to the custom code map that had recently been loaded in.The Tuner insisted the map was fine & that I must have a boost leak somewhere, & I replaced pretty much all the boost & vacuum pipework, plus a Forge007p, but couldn't stop the problem. Eventually I stumbled on a thread on Canadian forum where someone had the same problem & his tuner had found it was caused by an incorrect value in the software. I'd given up getting anywhere with the Tuner who'd put my map in & In desperation I got the Revo trial loaded, problem solved immediately no more 17705. I got Revo stage 1 a week or two later, & I never saw 17705 again.

Thanks for the info, as I said with the 17705 it doesn't throw a cell or seem to go into limp mode, so i'm not overly bothered about that 1 (although it would be nice to solve it), it was more the 16804 that was bothering me, as I assumed it would be a rear 02 fault thrown not the front.

I would still like to know, if the 02 sensor issue would / could cause the flatspot at low rpm though.

I would of thought a dodgy O2 sensor would cause fueling issues for the ECU so yes. Gunked up throttle body often cause flat spots, & 17705 too. If you haven't already done a throttle body I advise you do.