Chasing a ghost O2 sensor!

[Zash]

Hi Guys,

So, about 10 years ago, I bought a heavily modified for the track 206cc 2.0.

It required work, but it has worked great for a long time. It's always a pleasant surprise when I find something new in it.

It has passed its MOT without problem for the past 10 years.

Now, recently, a CAT emissions fault came up. I investigated to see whether or not I needed a new CAT or a new O2 sensor.

Well, PP2000 shows that the Downstream Sensor is always at 0v. I thought this must be the problem and bought 2 new sensors (in hopes of replacing both together).

Before that though, I tested the downstream sensor and it seems to work perfeectly. I swapped the upstream and downstream sensors and I still get 0v oon the downstream in pp2000.

I spent the entire day today tracing the wiring and testing to the ECU connector - the downstream O2 signal is live and present right into the ECU connector.

The ECU just doesn't detect it!


[img]https://i.imgur.c*m/Gb7En5T.jpg[/img]


It has really got me scratching my noggin...

So, it got me thinking:

1. Either the ECU is faulty, being unable to detect the second O2 sensor, even though everything else is fine.

2. The people who built the track car purposely reprogrammed the ECU to disable the downstream sensor for more power / prevent codes caused by high flow exhausts etc.


Question: Is it likely to be #2 or am I diluding myself? Is disabling the downstreamsensor done often as a mod? Does it affect MOT emissions tests? (if not then this would explain why the car has passed with flying colours for the past 10 years).



Thanks for any insight!

[Artermis]

My immediate thought would be the same as yours, it's been written out of the ECU map. I dont suppose you've any idea if it's had a remap in it's life?

[Capncol]

You don't say what the "heavily modified" bits are, so it's a guess, but yes, 2nd o2 could have been disabled. The injection system uses S1B1 as the fuel trim management, and S2B1 as the reference to confirm Cat and fuel trim is correct. Race cars usually only use a W Band o2, and no 2nd o2 sensor (and usually no Cat)

[Zash]

Thanks guys.

FYI, these are the modifications as per original listing 10 years ago. I know for sure some of them are lies, though others are confirmed truths (Copy-Paste):

It would be cool if someone would tell me how to confirm some of them...

!!! PUG 206CC !!!
Car is to be feature in Modified Motors july o6 [true]
centre spread
Too much spec too list but well over £15k has been spent on the mods inc

!!! ENGINE !!!
2.0LTR 16V
Mahle forged pistonsand con rods [unconfirmed]
shrick cams and followers [unconfirmed]
titanium valve springs [unconfirmed]
steal head gasket [unconfirmed]
nology leads and ground kit [True]
pug sports fuel pump with 4.5bar sensor [unconfirmed]
Dastek ECU withserial port [LIES!] - Standard ECU and can't find any piggyback.
Rev limit raised to 8000rpm [LIES] 7000 rpm as standard]
BMC CDA induction kit [Actually ITG Induction Kit]
Custom 5zigen manifold [unconfirmed] - looks standard to me, but what do I know
5zigen3.5" exhaust system [I replaced old rusted exhaust system with custom SS exhaust from CAT onwards.
SARD engine dress up kit [Maybe/unknown]
Braided horses all round all round [True]
All tanks polished [True]
Cusco water injection [True]
External fan [Huh? Where?]

!!! TRANSMISSION !!!
Custom built Quaiffe gearbox [unconfirmed]
With LSD front mount diff & oil coolers [True]
Titanium linkage
Polyflex bushes

!!! WHEELS !!!
16" SRD comp x magnesium alloys [No, though damn good SSR Type C Alloys]
205 / 40 / 16 Yokos

!!! BRAKES !!!
286MM AP racing 4 pots on front [True]
AP rear discs [True]
FSD brake bias adjuster [unconfirmed]

!!! SUSPENSION !!!
Cusco fully adjustable coilovers [True]
Polyflex bushes [unconfirmed]
Sparco strut bar [True]
Pug sport chassis tie bar kit [True]

!!! BODYWORK !!!
206 GTI GT front bumper [True]
Carbon fiber touring splitter [It was ripped off the week before I bought car, but shows in pics]
DTM cup mirrors [True]
Quad headlight conversion [True]
Full respray in VW gloss black [unconfirmed]

!!! INTERIOR !!!
Sparco torino red alacantara recliners [True]
other parts retrimmed in red alacantara [True]
sparco tri spoke steering wheel [True, though now replaced by me]
Sparco gear knob [True]
7 DEFI gages with link system [True - 2 separate systems]
one link controller in sunvisor [True]
Push button Start [True]
Head unit relocated in glove box [True, though bypassed - I rewired an Alpine unit it back to centre]
Performance meter in glove box [True]
DEFI link in glove box [True]
Cusco water injection controller [True]
lap counter [True]

!!! ICE !!!
Standard head unit
Kenwood components

!!! PERFORMANCE !!!
180 BHP [unconfirmed]
0-60 6 SECS [Lies - this is a hypothetical reading on a 4 wheel drive car taking into consideration 180BHP and car weight - 206cc is 2WD and timing would be a couple seconds more]
Top speed 140mph [So standard, I guess?]

!!! SECURITY !!!
Predator Alarm with remote start and pager system [Lies!]

!!! BUILT BY !!!
Ricky of RBM Motors & Chris Suttor of SQ Deign [unconfirmed]

!!! QUICK PROFILE !!!

6 pot AP Racing Brakes all round and Stainless Hosses [4 Pot as listed above, but true]
Fully adjustable Suspnsion [True]
Ecosse Kit [True]
Recaro Buckets and retrim in red Alcantara [Actually Sparco, but whatever]
Defi Guage Link System [True]
Full Stainless Exhaust inc Manifold [Cat is present. Unknown of manifold is custom, though rest of exhaust is custom SS I had installed]
Quaife gearbox and LSD [unconfirmed]
SSR Comp X 16' rims with brand new tyres! << check out the price of these! [No, SSR Type C, though very good]
The exhaust is Zigen right through to the head! [unconfirmed]
There are Peugeot sport titanium chassis tie bars underneath. [unconfirmed, doubt they are titanium, look like Steel to me]
Alloy radiator with satelite oil coolers, [True]

diff coolers and trans oil coolers front mounted. And yes it has Cusco water spray [True]
Nearly every pipe is SARD braided and the rest of the tanks are polished. [True]
Engine has a carbon ITG ram air and a mappable ECU. [ITG ram air = true, Mappable ECU, I doubt it so [unconfirmed]
Lots of Stainless and Polished engine parts [True]
AP Racing Clutch [Replaced with another after market by me]
Front and Rear Alloy Strut Bars [True for front, Rear [unconfirmed]]



Is there a place I can put this where people might be able to help be either confirm the unconfirmed mods?

Thanks!

[Capncol]

Someone would need to actually look at the car.
Engine mods Pistons/rods/cams would require stripdown to confirm.
Radical cams and cyl head would require bigger injectors, custom ECU such as megasquirt and these are obvious.
Due to std top speed (performance?) and rev limit, gut feel is std engine with dress up kit.