Lambda / oxygen sensor wiring loom

[Fefeu52]

Hi all,

It's now time for me to ask your help.

My 1992 S3C has been decatalysed (I don't know when). Catalytic converters were removed with the short exhaust manifolds. Long non-cat manifolds were installed with lambda nut welded on. Genuine lambda sensors are screwed on it. I'm pretty sure that there are the genuine one because they are Bosch brand, with the correct number, and the Ford plastic 3-pin connector.... Black, not white as I have seen here.

https://www.pistonheads.com/gassing/topic.asp?h=0&...

On the nearside, the sensor is well plugged on the car wiring loom. On the off side, nothing plugged. The sensor plug is free. When I replaces the spark plug some weeks ago, I have noticed that offside spark-plugs were lighter than nearside ones (too lean).

My problem is that I don't find any wiring loom to connect the second sensor. Should it come from the nearside, as the first one, ans go further to connect the second sensor ? Or should it come from the other side (offside) alone ? I don't find anything that could look like I'm looking for.

I already have the wiring diagram for 290 S, but for non-cat cars. I don't have any information about lambda sensors and specific wiring looms for it, no more than wiring colours for it.

All the best

[Fefeu52]

Thank you for your help Phillpot. I doubt my car would have a single sensor system. Why do they buy a brand new Bosh sensor just to plug a hole.... strange. Or the ECU could have been changed by an old Granada model that need only one sensor. I will have a look to the ECU number.

mentall said:

note: under UK regulations the lower CO requirements didn't come in until 1992, so we're OK without the cat, as long as the tester doesn't know that the car ought to have one! I don't suppose you have these problems?

That's exactly the same rules in France. Catalytic converter is not obligatory before 01/01/1993 except if it was installed before by the manufacturer. But testers in France don't know the TVR brand.... They don't know what is a S Sometime, they have never seen a RHD car How do you want they know an S3C has to be catalyzed ? That's not written on the V5 french equivalent.

Luckily, I have a picture on my phone to show.... The car is 100 miles from me during the working week.



Don't worry about the swirl pot, it has already been removed, blasted and painted with an epoxy paint. With the battery stand.

As you advice, I will test the warming function of the connected sensor.

In fact the car is running pretty well. 0.58% for the CO ratio few month ago, but I have several symptoms that tell me there is anything wrong. The car is running well when cold, and when warm, but between these two states, the engine tends to stall. The iddle speed is swinging.
Other symptom, when driving, when I put my foot down, the engine tend to struggle before seeding up (too lean). And as I already said, the 3 right-side plugs are lighter than left-side ones.

[Fefeu52]

Tanks a lot. I reassemble the pictures yesterday and Print it on A2 sheet. It's not easy but it is readable.

Could you tel me where you found the heater fuse holder (C-1135) ? Inside the car, near the ECU, or in the engine compartment ?

[Fefeu52]

OK, perfect. I will try to look at that this week-end.

[Fefeu52]

mentall said:

As an example: on my car there was NO WIRE in the harness going to ECU pin 1: Keep-Alive-Memory supply. Hence, no diagnostic outputs, and presumably not much adaptive control memory. I provided a (fused) feed from the radio supply, and now have diagnostics that do make sense

Thanks for the information, I'll also check that I want to build a default code reader :


Picture from here : https://passionford.com/forum/ford-sierra-sapphire...

And codes are there :

[Fefeu52]

Hi,

A little report of my afternoon work.

mentall said:

By the way, do you have the 88BB-12A650-LB ECU as I do, and some other S3C owners? This also seems to be correct in the Fordopedia reference list.

Yes, that's it :



On the connector, I founded the Blue/white on the #43 pin and Blue/Black on #29. The #29 is really easy to remove from the connector and the isolation is broken. So somebody tried to find a problem previously near there.



I found the fuse : with 2 black/red wires to power 2 sensors. The fuse is OK.
I tested the 2 warming resistances and both seems to be OK (3,6 ohm.... 40W seems correct)

Now I have to play to a new game : "Folow the wire"

The blue/black wire goes out from the passenger compartment with the main loom, nearside. In the engine bay, the loom divides in 2 parts. The first one go to the bottom to go in front of the engine (lighting and horn for example). The other part stays on top to go to the other side of the engine, going behind the engine, on top of the bell housing. Near the loom separation, the left-side lambda loom comes out from the main loom. Here I can find the blue/black wire for the right sensor.



The blue/black wire was going trough the behind-engine loom, then going back :eek, then going on :eek, and then going out to pass along the gearbox : And always with 2 other wires ..... Black/red and Brown



You can see the clutch sleeve.

So I found what I was looking for but I don't understand what it is doing here. I didn't succeed to pull on it. I think the plug is always on and a plastic collar retains it. I will remove the central console to access from the gear lever hole.

to be continued....

[Fefeu52]

mentall said:

Do you have continuity between pin 29 (Blue/Black) and the right Lambda sensor

I have not done yet.

mentall said:

Maybe the Blue-Black near the gearbox is something entirely different (though I can't see what it might be).

If the blue/black wire was alone, I could think it is used for something different. But the 3 wires are together (Bu/Bk, Bk/Rd, Bn), they are doing the same loop in the loom. There is no other Bk/Rd wires in the main loom that the 2 coming from the same fuse. The body has already been removed during the car life. It seems that the loom has been pull backward to go to a post catalytic HEGO.... Strange.... I'm pretty confident. The simplest explanation is the good one (Occam's razor)

mentall said:

Certainly the wire into the ECU plug shouldn't be loose: maybe worth removing the plug and doing a 'wiggle' continuity test from the cut insulation to the inside terminal?

Sure.

[Fefeu52]

mentall said:

Post-cat HEGOs ought to be at the front of the car too (close behind/below the cat).

I don't think the Cologne V6's ever had a 'downstream EGO' until 1994 when the 24 valve engine appeared in the later Scorpio, with EEC V engine management rather than the EEC IV that we have. Anybody who knows different please let us know...………

Yes, you know, and I do too.... but that's possible people who did that didn't know..... Can you consider driving a car with an HEGO not plugged and not doing anything to solve the problem ? I can't.... but some people don't mind. Can you consider driving a car with propershaft UJs so much destroyed that you can't go over 80mph without loosing parts of the car ? Some people don't mind... Some people does bullst, no use to understand why, I just have to repair .... and have fun as soon has the sun will come back

[Fefeu52]

Hi all,

I have news about my HEGO loom. I finally found the end of the loom...and the plug...there, on the right side of the gearbox



the plug was completely stuck between the chassis tube and the body. By pushing with a jack and a piece of wood, I manage to locally lift the body of few millimetres to liberate the plug and slide it back.

So I got it.



That's the good shape. The plug is not in really good condition, but it works. I just have to isolate the loom properly and reconnect all stuff.

[Fefeu52]

Hi all,

I just wan't to keep you informed. The second HEGO is now plugged. This week-end, I was able to turn ignition ON. After 5 minutes, both HEGO were hot, so the looms are now OK I started the engine too. I didn't noticed any difference, but it runs well.

Thank you for your replies. They really helped me