I have swapped over to the "good" lambda sensor, while doing that I thought it might be usefull to take a picture of the probes, together with a new spark plug.which has 50 miles on

Left to right it's the "1.0" good lambda, "1.25 lean lambda", spark plug. To my mind the spark plug looks lean which is even more confusing, consistent with the diagnostics, but not with the tailpipe results

With the "good" lambda fitted there are the following results, all on idle:

001, box3, 0.0%

030, 110,110

031, box 1 varying from 1.05 to 1.15, generally 1.05

032, as before 0.0% and 9.8% as there has been no running to readapt

033, 0.0%, varying from 1.64v to 1.76v which seems consistent with the lambda readings from 031

036, 0.78v steady

Returning to the air leaks question, then can i just make sure I have not missed anything. As I see it there are the following potential sources of air

leaks:

Throttlebody to inlet manifold

Inlet manifold

MAP sensor on manifold

Pressure pipe between MAP sensor and fuel regulator

hose from throttle body to brake servo

hose from throttle body to evap valve solenoid

Sorry, I thought I should add the error codes from before the lambda swap

16555 - Fuel Trim: System Too Lean: Bank 1
P0171 - 35-00 - -
16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
P0130 - 35-10 - - - Intermittent

Edited 2 August, 201412 yr by 937carrera

As far as I read regulation and control is, "regulation" is when it's using the info from the lambda too adjust the mixture/timing and "control" is the ECU is seeing a reading from the sensor that's out of it's normal range and so it's defaulted to a stored value??

In block 041 does it say "Htg bC ON" ?

Most of the fault finding keeps coming back to unmetered air leaks or injectors leaking

032 the varying in figures could be fuel contamination in the oil !?

cracked exhaust manifold/gasket leak ?

Those figures look better, still puzzled by 030 unless the last digit being a 0 means its in open loop not closed loop 1 ?

As far as those air leak points cant think of any others, on mine one of the rubber hoses from the TB had a split in it that until it was off the car and flexed you couldn't see it ?

OK, so

regulation = closed loop, meaning the a/f is adjusted using the lambda readings and

control= open loop, meaning the stored map is used

In block 041 both blocks say heating is on, they stay on all the time as I have never seen them switch off, maybe because the cat never gets hot enough ?

I have already swapped over the injectors, but not observed the spray pattern, maybe that's something I have to do

Judging by the condition of the evap pipe I think that has been replaced recently, it looks almost new. I have had the servo pipe off already when I shortened it to eliminate the split at the connection point. Despite axamination I believe both of them to be in good condition. The car hasn't done 1000 miles since the oil change

Did you have any thoughts after looking at the picture or the DTC codes i edited above. I agree that the latest values look better, but the harsh reality is that the CO will have gone from 2% to 6% as a consequence of the lambda sensor change.

The P0130 chk heating circuit, chk probe regulation theses might of been logged during you replacing the sensor?

P0171 fuel pressure regulator & holding pressure, Injectors, intake air leaks, pre cat probe regulation as above, charcoal filter valve, exhaust system for leaks & vacuum pipes for leaks.

Regarding the injectors I think there looking for them leaking under pressure rather than spray pattern.

Have you tried getting someone to drive it while your monitoring the parameters? or use the vagscope ?

The pics of the sensors the "lean" one looks contaminated?

To eliminate the evap you need a small pair or plastic brake flexi pipe clamp or a small mole grip plyers to squeese the pipe closed.

Well, after some more time looking at vagcom I decided to swap over the first lambda sensors again and see what happened. Apart from now looking white rather than black the results from vagcom were pretty much as expected with the lambda values varying from 1.25 to 1.2998. A weak lambda combined with a rich tailpipe told me that the ECU just wasn't seeing reality so I decided to start the diagnosis from the beginning again, focussing on the first lambda sensor and using the Elsawin guidance.

The approach paid off. By starting at the beginning again and carefully carrying out each test I discovered than terminal 3 of the connector did not have the required 12-14 v. After carefully checking again and following teh wiring diagram, what I realised was that the connector was not wired up correctly, pins 1,3 and 5 were transposed with pins 2,4 and 6.

When I first got the car as a non runner only one of the 6 pins actually had a wire connection and one of the jobs i did while the engine was out was to rewire the lambda plug. I suppose my pathetic excuses would include working upside down with short cables with a connector I hadn't worked with before.

I finished rewiring by inspection lamp last night and got up early this morning to test all 5 connections to the ECU and the ignition feed. I fired the car up and within 5 minutes the first lambda had gone into closed loop mode and was regulating between 0.99 and 1.01 lambda

I have done some running around and the car is much more responsive, especially above 4000 rpm. Both the lambda sensors are passing tests, the lambda voltage is around 1.52 volts, however the catalyst test 046 is not passing with error 16804 : Bank 1: Efficiency Below Threshold. I also can't get the test for evap purge test on block 070 to initiate manually, but think it should pass the test again after a bit more driving around

I have yet to take the car for an emissions test, but on my old Gunson CO meter the CO was down to 0% so that's a good sign

With the benefit of hindsight I don't understand why it took me such a long time to realise the very basic mistake I had made. I suppose you call it experience.

Many thanks for all the help, suggestions and downloads that helped me get there in the end

Well that's good news then !

Have a look at this file I used it to fault find a friends Mondeo that was continually throwing up the "Cat below effieciency" codes

Cat below efficiency test.pdf

I'll let the car get some miles under its belt and then have a look at the cat efficiency. I'm a bit fed up of putting it up on axle stands almost every day so it will be good to do some driving, rather than fixing the car.

i took the car along for an emissions test today................. all green delighted isn't the word

glad that you got it sorted buddy :)

i m having very similar results in vcds, i have gone through your post and did the same test and i also have 2 new lambda sensor and i get the same results for both as your new one.

you said that the wires in the plug where wrong, my loom was a second hand one, and the seller happened to have two so this sent alarm bells ringing when you said that. i am wondering if they played around with the plug as it looks like someone has taken the pins out before.

where did you get the correct pin info from?

i have the old connector and pigtail from my original loom (which worked perfectly) and its pins are:

1.blue

2.white or grey

3. white and red

4. brown and red

5. blue and red

6. again white or grey but with red tracer.

this to me looks correct because on the sensor 3 and 4 are the heater circuit

on the car loom the connector is damage and quite shoddy looking, but pins are

1. brown and red

2. yellow or white and red

3. green

4. green and brown

5. green and white or grey

6. green and grey

the wires are oily and must have got hot because the light colours are hard to see.

this to me looks wrong because as above on the sensor the heater circuit is 4 and 5 but the thicker wires are now going to pin 1 and 2 which is a black wire and a blank pin on the sensor.

any help on this would be greatly appreciated as a am in the same boat as you and have spent a large amount on new parts and a massive amount of time and effort on getting this thing running.

I've just posted a reply on your other thread. The wiring info came from the reading VW diagrams. One thing that I have noticed this morning is that the 6 pin connectors are wired differently for the ARC and AUA engines, so you do need to refer to the wiring diagram I posted in your thread

Well that's good news then !

Have a look at this file I used it to fault find a friends Mondeo that was continually throwing up the "Cat below effieciency" codes

Hi Nige - the link has ceased working, any chance of a fix please?