No Cat, No Oxygen sensor.

[Spyda]

Ive read on Vortex that you can use just about anything. People use ford o2 sensors as they are about one third the price of a digi mk2 sensor.

Are you sure your ECU is digi 2?

I know you can use a mk3 sensor on a mk2, the forth wire is just an extra earth, the rest is the same.

[ryana89]

I am fairly certain that its a Digi 2 unit.
On top of the ECU it states that it is Bosch (of course) and Digifant, but it also has the code "DF1" on the sticker/label.
And according to wiki, that was the ECU module used on Cabrio Golfs with a 2E engine. (do I trust wiki)

Keep in mind I dont have a standard Mk2 and that my O2 sensor harness is a 4 wire one. (Apparantly similar to a MK3 one)
Could sombody link me up with an explanation on how Generic O2 sensors work? I understand how an O2 sensor works, but I don't see how one not intended for a car is going to do anything but send the wrong signals (Ie to lower voltage or to higher voltage).

Thanks

[ryana89]

Ok, its been a while but I've done the rounds with a few other Auto sparkies in the town.
I asked them "how do you recognise a 4 wire oxygen sensor plug if you're uncertain if it is one and how would the voltage/resistance act?", then "If you can identify which wire does what, can you hook the wiring up for me?".

I went to a (trusted) Auto Electrican who, was willing to have a look over of the car and actualy speak with me, but he said he would not be able to definativly connect the 4wire O2 sensor that I have without wiring diagrams. Ok, atleast he came out to my car and spoke with me.

Next was a man with experience with German/European cars, I asked the same questions again and he would not discuss the topic at all with me, stating "If I gave you advice, you'd probably forget it....". Mate, not the question I asked, I simply wanted to know if he could do the job or not. He wanted $$ before answering anything.

Can anyone here offer advice on voltages/resistance on a 4 wire oxygen sensor? The 2 white wires are for heating, the grey wire is earth and the black wire is a signal wire on the O2 sensor. What 'signal' would the ECU send down these wires that can be measured with a Multimeter.
Keep in mind the plug in the engine bay has 4 wires of the following colours Green/Red, Yellow, Brown, White/Blue.

Thanks.

[peedman]

Mate its really hard to confirm what goes to what because your wires are different colour to mine. On my desk here i have an ibiza cupra connector and they are

#1 - Red/white
#2 - Brown/black
#3 - Green
#4 - Black (which is definately the signal)

I can tell u that on the o2 sensor plug for a mk3 or ibiza that pin #4, which is the pin separated by a tab, is always the o2 signal wire. It can be different colours tho depending on the year.

You should try and decifer from these links, i had a look but i cant confirm anything.

Motronic Pinout
Fusebox FAQ - Club GTI
Installing an Air Fuel Ratio Gauge

Btw did u end up buying an o2 sensor? Ive got a spare (used) one like the from gap that i can send u if u pay for postage

[ryana89]

I understand the difficulty trying to diagnose problems over the internet, but hey you've helped me out more than the 'professionals' I've met so far.
The MK3 Ibiza ran a 2E with Digi 2 didn't it?

I went through another of the wiring/colour charts on the A2 resource website and no colours match up at all!

I did end up buying a MK3 o2 sensor with the spacing/tab between wire #3 and #4 (not the one I wanted of course).


Let me see If I can clarify things with some more infomation
(Assume)

#1 - Green/Red
#2 - Yellow
#3 - Brown
#4 - White/blue



With engine running and a multimetre set up so that positive needle on multimetre is on the positive battery terminal.

Negative needle goes on the following wire's, results/voltages shown.
#1 -8.5 volts
#2 - 2 volts
#3 - 0
#4 - 0

When positive needle is placed on #2 and negative needle placed on #1 - 6.4 volts is shown.

This is with the engine still cold and at idle.
Chances are that information wont help at all but you never know

Thanks

[ozvino]

Ryan, isn't your car Sth African? Have you tried anyone in Sth Africa?

Maybe email these guys and ask the question; Google is your friend........

Volkswagen Engine Installations & Upgrades | Johannesburg

Dave

[peedman]

When you say that u found this plug near the 4th cyl runner do you mean on the passengers side or the drivers side? Just trying to clarify because the cylinders are 1 2 3 4 when looking from the front of the car so the 4th cyl would be on the passengers side. The o2 sensor plug is normally found on the drivers side.

Other than that i cant really help you. Ive looked it over and over and each time i reach a conclusion i realise i am wrong and get more confused.

If i were in your position i would wire it up as you see it i.e. like the mk3 plug and see if it works. After all there are only finite number of possibilities!

[ryana89]

Certainly is a South African car.
There are no details (in the service books) about where/when the 2E was converted into it, I only have the address from where it was first sold (which is now a car rental place).

I've been googling since the day I bought my car
Unfortunatly this is the only question I cant find an answer too

[ryana89]

When you say that u found this plug near the 4th cyl runner do you mean on the passengers side or the drivers side? Just trying to clarify because the cylinders are 1 2 3 4 when looking from the front of the car so the 4th cyl would be on the passengers side. The o2 sensor plug is normally found on the drivers side.

Other than that i cant really help you. Ive looked it over and over and each time i reach a conclusion i realise i am wrong and get more confused.

If i were in your position i would wire it up as you see it i.e. like the mk3 plug and see if it works. After all there are only finite number of possibilities!

Yep, on the 4th intake runner closer to the passenger side.
I'd hapily hook the system up, but I'm worried if I wire it wrong, I could do damage to the, rather rare, ECU.
I cannot think of what else this plug could be for, and thats why I'm assuming its for an o2 sensor.

If I can't figure this out, my only option is to drive to Sydney and see Loon.
I wonder how easy a K-jet conversions is......

[peedman]

Having spent the good part of today sorting out my wiring harness i tend to agree with u that its for an o2 sensor. I dont recall any 4 plug harness in the engine bay other than the o2 sensor if anyone else can chime in. It just happens that urs is located in a different place than the usual!

I wouldnt do a kjet conversion as you would be going back a step from efi. Have u scanned the car for any codes btw, that would be a good idea and should bring up any fault codes.

[mikinoz]

Hey, here is some help.

Your ECU is MK2 Digifant - but there are 2 different Bosch units and a Siemens unit. I had up until recently the same one as you.



You need to run an O2 sensor as the car wants a reading so as I understand the reading will be inifinite currently and reading that it is ultra lean...

1. General Description - 1.4 Digifant II Engine Management System

1.4 Digifant II Engine Management System

The Digifant II engine management system-so called because both fuel injection and ignition are controlled by one integral system-includes fuel injection that is completely electronically controlled. As illustrated in Fig. 1-1, several sensors supply information to the central electronic control unit which then electrically operates the solenoid-type fuel injectors. Fuel is metered to the engine by controlling the amount of time that the injectors are open. All functions, including the amount of fuel injected, are controlled electronically by the control unit.

Fig. 1-1. Main components of electronic Digifant II engine management system.



For more detailed information on the fuel injection functions of the Digifant II system, see 7. Digifant II Fuel Injection. Additional information on the oxygen sensor system and other emission controls is covered in EXHAUST SYSTEM AND EMISSION CONTROLS. The ignition functions of the system, including the knock sensor, are covered in IGNITION.

And this is the critical detail...

=5. Oxygen Sensor System

The oxygen sensor system provides the fuel injection system with information about combustion efficiency by measuring the oxygen content in the exhaust. The exhaust-mounted oxygen sensor is constructed of ceramic material coated with platinum. One surface is exposed to the exhaust gas, while the other is exposed to atmosphere. The difference in oxygen content between the two surfaces causes a chemical reaction which generates a low-voltage signal (100-1000mv). This signal is monitored by the control unit which, in turn, signals for changes in the air/fuel ratio in the fuel injection system.

Since the oxygen sensor system relies on low-voltage signals, it is very sensitive to contamination or poor connections. Making sure that the electrical contacts are clean and dry may cure system problems easily and preclude the need for time-consuming testing.

Because the oxygen sensor system is different for each fuel injection type, the repair information in this section is organized according to fuel injection type. For help in identifying the fuel injection system, see FUEL SYSTEM-GASOLINE.

Replacement of the oxygen sensor is a scheduled maintenance procedure. The specified replacement interval varies depending on model year. On 1985-1987 models, the sensor's replacement interval is signalled by an indicator light on the instrument panel coming on as a service reminder. After the oxygen sensor is replaced, the mileage counter must be reset. On 1988 and later models with oxygen sensors, the service reminder light has been omitted. See LUBRICATION AND MAINTENANCE for more information on the oxygen sensor replacement interval and the mileage counter resetting procedure.

Send this to your mate who has 20 years experience, the knock sensor diagram from the bentley...

1.2 Knock Sensor System

TCI-h ignition with knock sensor differs from the basic TCI-h system with the addition of an engine knock sensor and knock sensor control unit (Fig. 1-2). With this system, the distributor has no vacuum or centrifugal advance mechanisms. All adjustments to ignition timing are done electronically. The knock sensor system detects pre-ignition or detonation (commonly called knock or ping), and adjusts ignition timing electronically to eliminate it. The system also makes the timing advance adjustments which are necessary at higher engine speeds.

[mikinoz]

Here is a picture of the sensor and the connector on my MK1. (behind the headers, no cat)



The sensor is generic and has been spliced in to the connector before the plug (hard to show).

[mikinoz]

Some manifolds have the connection for the O2 in them, not on the pipe.

Finally, here is how you test the O2 on Digifant and it has a pic of where the connector originates.

5. Oxygen Sensor System - 5.3 Testing Oxygen Sensor System (Digifant II and Digifant I) - Testing Oxygen Sensor Function

Testing Oxygen Sensor Function

This is a sensitive measurement. In the interest of accuracy, the engine must be fully warmed up, with idle speed, ignition timing, and CO content adjusted to specifications. The exhaust system between the engine and the catalytic converter must be free of leaks, the engine coolant temperature sensor should be connected normally, the voltage supply to the oxygen sensor heater must be OK, and all other electrical consumers including air conditioning should be switched off. In addition, test measurements should only be made when the radiator cooling fan is not running.

Run the engine and record a baseline CO measurement. With the engine running, raise the engine oil dipstick slightly. This allows extra air into the closed crankcase ventilation system and, therefore, into the intake manifold. If the oxygen sensor is performing correctly, the CO reading should drop for a few seconds, then return to the original value.

NOTE-

For Digifant I electrical tests see FUEL SYSTEM-GASOLINE.

To check oxygen sensor wiring (Digifant II only):
1. Disconnect the harness connector from the Digifant control unit, as shown in Fig. 5-7.
Fig. 5-7. Digifant control unit and oxygen sensor showing mounting and harness connectors.



2. Using an ohmmeter or a multimeter set to the 20k scale, check continuity between terminals 2 and 13 of the Digifant control unit harness connector. See Fig. 5-8. There should be no continuity. If there is, there is a short to ground in the oxygen sensor wiring.
Fig. 5-8. Digifant control unit harness connector terminal identification.



3. Disconnect the oxygen sensor harness connector. Connect a jumper wire between ground and the green wire (terminal 1) on the harness side of the connector. There should be continuity. If not, there is a break in the oxygen sensor wiring between the harness connectors.

Hope that helps!

[ryana89]

That does help

3. Disconnect the oxygen sensor harness connector. Connect a jumper wire between ground and the green wire (terminal 1) on the harness side of the connector. There should be continuity. If not, there is a break in the oxygen sensor wiring between the harness connectors.

I think that may be the most helpful part.

Is that above piccy stating that terminal 1, 13, 14 and 25 are all individual wires that go to the oxygen sensor?
Because that is what my entire problem is, I have a 4 wire plug that I have no idea which wires are doing what (Ground, signal, heating).

What I still don't understand is that I thought Digifant 2 only ran a 3 wire o2 sensor?

I wouldnt do a kjet conversion as you would be going back a step from efi. Have u scanned the car for any codes btw, that would be a good idea and should bring up any fault codes.

Currently this "EFI" is using 15L+/100k
Unfortunatly Digifant 2 isn't capable of storing fault codes

[mikinoz]

What I still don't understand is that I thought Digifant 2 only ran a 3 wire o2 sensor?

Head to the ECU and follow the cable that should go to the O2 sensor and see if that is what you get to. I am of the opinion digi2 is 3 wire (2 white for heating and a green signal) But you don't know what has been going on. If you trace it and find a 3 pin connector you will be more happy I'd say the 4th pin if there is would be a ground?

KJET is not viable as you need to replace heaps more stuff and this is going to be hard initially, but it will get sorted.

*please remember I am as much a mechanic as a brain surgeon, so take my advice accordingly.

Paging JMAC!!