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Discussion Starter #1
I'm confused with the oxygen sensors.

I looked at RAVE and on section 19 page 14-> of the workshop manual it shows the Engine ECM connectors and what the relevant wires are.

Looking at the middle connector (red one) C507 it says the following pins are to do with the Oxygen Sensors:

Pin 8 - Bank B Upstream
Pin 17 - Bank A Downstream
Pin 33 - Bank B Downstream
Pin 34 - Bank A Upstream

I have a UK 1998 4.6 HSE which pins should have wires?

On mine Pin 8 and 17 don't have any wires going to them, pin 33 and 34 do have wires going to them.

I connected the Multimeter to the negative terminal on the battery then probed pins 33 and 34, 33 just stayed at 0 all the time, pin 34 varied whilst I was watching it went between 0.1 and 0.7 volts.


If it makes any difference the MAF is disconnected as I clean it (although it doesn't seem very dirty) - I have managed to start by applying some revs, as without revs when the MAF is disconnected it just dies, after a couple of seconds I can leave it to idle although the idle feels a little low.

I also tested pin 15 which is the TPS, that gave me 0.65 volts on idle going up as I revved, I then turned of the engine and tested full movement which appears to function perfectly with no dead spots all the way up to 4.57v

So questions are:

Should it just be pins 33 and 34 with oxygen sensors connected? (the upstream and downstream terminoligy has me confused!)

Does the fact that I can't get a reading from Pin 33 indicate that, that sensor is dead?

Does the Pin 34 reading look OK?


Thanks in advance
 

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Discussion Starter #2
If I understand correctly, upstream is between the cat and the engine, and down stream is between the cat and the tail pipe.

Both my sensors are between the cats and the engine so I would have thought they were both upstream. Is that correct?

And on that basis they should be wired to pins 34 and 8 on the Engine ECM?

But I have no wire going to Pin 8!

Any ideas where to go from there?

HELP!
 

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Discussion Starter #3
I've got to say I think the RAVE data is wrong unless I misunderstand the terminology.

According to the electrical troubleshooting manual it is pin 33 and 34 which are used on UK vehicles. Pin 33 is the right heated oxygen sensor, pin 34 is the left heated oxygen sensor.

So it appears that my right one is dead (next question is that right as you're sitting in the car, or as you stand in front of the bonnet?)

Is it just a case of swapping it out for another?

Is one dead oxygen sensor likely to make it overfuel so much?
 

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Discussion Starter #4
Re-testing them,

I get left hand (which is from standing at the rear of the vehicle I believe) showing between 0.1 and 0.3v on idle

I get right hand showing between 0.1 and 5v on idle going up then back down again

So it actually looks like the passenger side (RHD) sensor is duff and not registering correctly - only going up to 0.3v

Again is this likely to cause my problems?
 

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2002-2005 Range Rover MkIII / L322
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I didn't read the whole conversation you had with yourself, so excuse me if I missed it... but it was my understanding you need to test O2 sensors with an oscilloscope to see if they're working correctly.

Are you getting a code thrown?
 

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Discussion Starter #6
:lol: I do feel like I'm talking to myself - it helps though sometimes!

I read that you can test them with a digital multimeter but it wasn't as accurate as a scope, you just can't test them with an anologue multimeter.

The multimeter shows there is something up with them as the ranges are so vastly different, I'm just not sure which one is right. From my latest reading I think the one with lower values is most likely to be correct. The last thing I read is:

The Stoichiometric Point is 450 to 500mV The voltage decrease to between 100 and 500mV if there is a lean mix. The voltage increases to between 500 and 1000mV if there is a RIch Mix. (data from Workshop Manual RAVE)

So the left hand bank is idling between 0.1 and 0.3v which suggests it thinks that side is lean and is increasing fuel.

The RIght hand bank is idling between 0.1v and 5.0v which suggests it thinks it is too rich and is trying to reduce fuel.

(That is all at idle when it isn't smoking at all!)

Now just to confuse me further later in the same workshop manual it gives the specs for the inputs on the ECM (from the outputs of the oxygen sensors) here it give 0V(Rich) - 5V(Lean) which puts the other one in spec.

So I don't understand!

No errors shown in the car and it's not illuminating the MIL, my OBDII interface should arrive tomorrow
 

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1995-2002 Range Rover P38A
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Hi

Took some measurements with the faultmate of the oxygen sensors. The faultmate screen also displays measured values per loop similar to taking values with a multi meter. The value changes continously between 0 and 5 V showing that the ecu is working properly and continiously switches between lean and rich. I tried to upload the file in the following link:

http://s79.photobucket.com/albums/j134/ ... v&newest=1

I am not sure whether the measurements are during driving or at idle. I hope it helps you.

Regards

Jos
 

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Discussion Starter #8
Thanks for that, my obdII cable arrived today so I'll see if I can get any similar data
 

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It seems that if you are spending all this time trying to figure out if one is working, I would just buy some new parts. Get genuine Bosch as the cheapos tend to throw codes and don't heat up quick enough. They only tend to last 80-100k miles. Seems like it is too much a headache to troubleshoot them.
 

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As I've always know it to be in every vehicle manual I have, right and left sides are determined by the view sitting in the drivers seat behind the wheel as though you were driving. But my experience only applies to NA market vehicles.

I kinda agree with spike, if your engine and the sensors are over 100k, replace them.
 

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If the Lh sensor is staying down at 0v or close to it then it must be working as its natural output is 5v.So its most likely that the Lh bank is just running constantly rich.This could be caused by a partial misfire,dribbling injector/s,(Highly unlikely) or possibly that the long term trims wont allow a narrow enough injector pulse to make it go up to 5v - lean.Buying new sensors is a total waste of money,esp when the Rh sensor IS switching,so just to put your mind at rest you could just swap the sensors bank to bank.
I have a 96my 4.0 Gems on the ramp right now with running problems.The garage that gave up on it had correctly diagnosed a faulty AFM,and sort of fixed it by fitting a cheapo,( The customer was billed £200) replacement.When it sort of fixed it they then said it needed a new Gems unit - at £2000. :shock:
Point of all this is that when I fitted my secondhand test AFM the car ran better but at idle both oxy sensors remained down at 0v,it just couldnt trim down enough to get them switching.A quick adaptive reset and an idle bypass adjustment and it now runs like a new car.
 

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Discussion Starter #12
Thanks for that Ally,

I've got as far as plugging the OBDII lead in and using EasyOBDII to check any faults which it says there are none stored - not sure if that is a good thing or a bad thing!

Which side do you think IS functioning correctly? the 0-1v side or the 0-5v side?

Two bits of the RAVE manual seem to differ, one says the readings should be between 0 and 1 volts, then later in the same manual it suggests they should be between 0 and 5 volts.

I've still got to setup some software to read live data properly.

Have you ever seen a v8 with symptoms like this? I'm going to check all the plugs for any signs as soon as I get chance. Would it make big clouds of smoke if one cylinder wasn't sparking?

Thanks for all the help!
 

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Discussion Starter #13
I just had chance to check some of the spark plugs before the rain got too heavy,


This is from my perspective standing at the front of the car.

The first on the left (closest to the bumper - drivers side RHD) was fairly black
Second on the left - was black not quite as much as 1st
Third on the left was very black
Fourth on the left was like 2nd

First on the Right was mostly brown with a little black

Stopped there as I was getting wet and they were getting harder to get to.

So it looks like it's the drivers side, which I think was the side going between 0 and 5v is the side which is overly rich, but would you expect them all to be black? The third one was the worst so should that be my suspect cylinder?

Does that help with any further analysis?

Thanks for sticking with me through this! :thumb:
 
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