General 2001 Brava 1.2 lambda sensors

[bluejohn125]

Advice needed.... basically - which sensors connect to which connectors on the wiring loom?

I have a 2001 Brava 1.2 with the later "Maniverter" exhaust that has 2 x lambda sensors. One is before the Cat section, the cable is 300mm long and was replaced about 4 years ago. The second is in the traditional place after the Cat, the cable is 600mm long and it could be original. Both are 4-pin.

Last year 2 things happened:

Firstly I overhauled the cooling system so I replaced the thermostat, this meant removing the coilpack and disconnecting the 2 x lambdas. However I MAY have cross-connected the sensors... Anyway the car seemed to run fine.

Then I took it to a garage for an MOT etc.. it passed fine but I was told that there had been an engine warning light and the diagnostics indicated a failed lambda heater (don't know which one).

Then... in the winter when warming up it would sometimes show the orange light and judder quite a bit, but it would clear up fine as the car warmed.

So.... I rechecked my lambda wires and connections, and swapped them over. I now have the upper sensor going to the higher connection on the loom, and the second sensor going to the lower connection on the loom - seems logical... The car basically runs very well (no lights) but sometimes there is still a hint of a misfire.. again when cold.

Therefore... can anyone please confirm the correct connection arrangement? I'm kind of assuming that they are now connected right but maybe the original (lower) lambda has a faulty heater that makes it misbehave when cold.

Any thoughts?

 

[Adrian Bravo]

Hey bluejohn,
I think I have what we need to differentiate between the two plugs. You could use a multimeter and test the pins back to the ECU plug, since the pins are easily identifiable on the ECU's connector block.

The two parts are numbered 141 and 360 for the lambdas





I wanted to say you could look at the colour coding on the wires but I have not figured out how the digrams express the colour coding system if at all.

Let me know how you get on

 

[bluejohn125]

Cheers for that Adrian, pretty comprehensive....

I should be able to figure out which plug is 141 (Top sensor, Heated) and 360 (bottom sensor) with all of this, won't use the multimeter though!

From the diagram it seems that the 2 connectors are quite separate - 141 is on a branch with 168(timing) and 279(temp sender), and 360 is on a branch with 136(detonation) and 137(speed).

Also the colours should help out if I can see the wires, from my knowledge of Italian I would estimate the codes to be :

R Rosso Red
G Giallo Yellow
N Nero Black
B Blu Blue
V Viola Purple
Z ??? ????

GR Either Yellow&Red or Grigio (Grey)
GN Yellow&Black
RZ etc
ZB etc

Probably the same codes as in the owners manual.

I'll report in due course. It could be that the newer, heated lambda has indeed failed... don't know how common or significant that is.

Regards

John

 

[Adrian Bravo]

Yeah I was thinking about the colours on the way to work this morning and thought... its in Italian

 

[Adrian Bravo]

Just found this colour coding list while flicking though the manual,

 

[bluejohn125]

Sorry I didn't update on progress...

I had a root around 2 weeks ago, It's not too easy to trace the cables by identifying "trees" of cables.. they all emerge from the black trunking at various points and go to indeterminate places..

Anyway I am fairly sure that I have the right connector going to the right lambda, except that the colours / pins did not match the list you gave. One connector had more mixed colours on it, but I could not be sure so I made some notes and gave up.

It's still not running quite right, I'll investigate further but it's probably going to a garage anyway, got a couple of other jobs needed...

PS

B = Bianco = White !
V = Verde = Green !

maybe I will figure it out.

 

[bluejohn125]

Well finally got it basically sorted...

I had another go at the connector confusion armed with the colour translations, still nothing quite matched but one connector made 90% sense so I swapped them over again (to my original configuration). I started the car up and it fired fine and seemed OK, so I switched off and left it.

Then yesterday I went to start it and it was terrible, so I swapped the sensors around again and it drove off fine but not perfect.

Left it with an auto-electrician I've used before, they cleared down loads of faults, checked the connections and left it running for ages while revving and monitoring it. Basically they could not get it to fail and give a fault, and it idled nicely. They did say that the Lambda was just very slow to switch, and it was a Hitachi that the last mechanic had spliced to the original connector.

So essentially it is running fine now, but I will get myself a nice new proper Bosch sensor and fit it myself. I've had 4 1/2 years out of this one, may as well get the best fuel consumption these days...

 

[bluejohn125]

Finally Finally... (hopefully).

Ordered a new Bosch Upper Lambda from Ebay for £60 odd delivered, it arrived yesterday after the bank holiday. There are cheaper "compatible" ones out there but for the price I though why bother faffing about soldering wires etc. Bosch are the best, NGK are also reputable..

It looked quite different from the Hitachi that failed but it went on fine, and a quick test drive showed that the car is running great and the annoying judder and hesitation is gone.

Should help fuel consumption too...

 

[bluejohn125]

Well this story is finally over too (I hope)....

The car was still showing a slight misfire so I got it diagnosed again... this time they found a failing plug lead that was jumping the spark to the cylinder head and therefore giving a weak spark in the cylinder! I now suspect that this was the cause of my misfire symptoms all along, I probably disturbed something when doing other maintenance and provoked the failure.

I checked an old set of spare leads I had lying around but these were failing too... these definitely seem to have a limited life, possibly due to the higher temperatures around a modern 16V head compared with older engines where they clipped on the side of the engine in lots of fresh air.

Anyway a new set of plug leads seems to have got everything running nicely again. In the old days they would have been one of the first things to change as a matter of course, but now the temptation is to think problems are cause by the engine management or one of the many sensors...