Lambda / oxygen sensor wiring loom

[mentall]

Fefeu52 said:

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.

That sounds OK: same as the diagram, same as mine.

Do you have continuity between pin 29 (Blue/Black) and the right Lambda sensor? Maybe the Blue-Black near the gearbox is something entirely different (though I can't see what it might be).

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?

[mentall]

Here's my old ECU pinout diagram: don't know if it's any help.

column 1 is the ECU on my car AS IT WAS originally, colours in English.
column 2 is the Sierra diagram. Colour abbreviations in Deutsch.
column 3 is from the Sierra diagram and some other notes I found.

Lines in red are connections that did not agree with the diagram: you can see the R-L HEGO sensors were reversed.

I gave up using this diagram when I found I could use the Sierra diagram directly.

[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.

[mentall]

Fefeu52 said:

It seems that the loom has been pull backward to go to a post catalytic HEGO

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...………

But then, you'd have a 24V 'Cosworth' engine! And a different ECU, with three-digit fault code output (my diagnostic device shows three-digit codes, but only up to '099'.

[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