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Generation 2 Pajero NH - NL Models 1991 - 2000

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Old 28-05-10
Rendrag Rendrag is offline
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Default Dud o2 sensor??

Hey folks,

So dash pod is all sorted... with a hitch.. My AFR gauge isn't working, so I shoved a multimeter onto the line coming back from the o2 sensor this morning after warming the car up.. - instead of the expected 0.05 - 0.9v, I'm getting -0.02 - -0.035v.. yes, negative voltages.. - can this be caused by something in the heater supply or such being broken? or do I have a dud o2 sensor??

But if it is a dud, wouldn't I have noticed the car not running properly? (3.0L '94 NJ)

Any thoughts?

Cheers,

Damien
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Old 28-05-10
Rendrag Rendrag is offline
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Ahh, just facebooked that it was playing up, and got a reply fro mthe mate I bought the car off.. - apparently the o2 sensor died about 60k km ago, and he replaced it with another bosch one.. - so the highly entertaining splice job into the loom wasn't stock mitsu Will take another look at the join to see if there's a bad joint there
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Old 28-05-10
Rendrag Rendrag is offline
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Hrrm, all looks good (so looks bad for the sensor... - are they a 'generic item'? can I just grab a (cheap) one for a commodore ($40) rather than needing one specifically for a paj ($120) ?

Though bit confusing that the green shielded+2 wire cable that goes to the ECU somehow becomes a four-wire cable at the socket underneath that the o2 sensor connects to.. would love to know where the joint for that is!
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Old 28-05-10
Rendrag Rendrag is offline
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Hrrm, oh well, good news is that on the workbench, the sensor tests fine.. - so now time to go hunting through the loom to find a break somewhere?!
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Old 28-05-10
Rendrag Rendrag is offline
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bizarre, found were the wiring for the starter/gearbox/O2 sensor/etc come into the car.. - real easy to get to place (not) - under the centre console just in front of the gear lever! Cleaned the contacts of the big 50-something pin plug there, and I can get a correct reading from the O2 sensor there... but the reading there doesn't make it to the ECU. and no sign of that weird green shielded cable there either... more searching to go!
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Old 28-05-10
Rendrag Rendrag is offline
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*cough* ok, so for future reference.. if you're getting a very small negative feed to yoru ECU from the O2 sensor.. chances are whoever last replaced the O2 sensor (such as your best mate who you bought the car from.. yep, he aint gonna live this down anytime soon..), tried to account for mitsu using white as signal, black as earth (where as the sensors usually use black for signal, white for earth), but switching the wires around when he wired in the new sensor.. but didn't realise that the plug where it plugs into the loom switches the wires for you...

re-soldered teh wires coming out of the O2 sensor the correct way around, and it's all working great! looking forward to seeing a difference in fuel economy!
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Old 28-05-10
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Quote:
Originally Posted by Rendrag View Post
*cough* ok, so for future reference.. if you're getting a very small negative feed to yoru ECU from the O2 sensor.. chances are whoever last replaced the O2 sensor (such as your best mate who you bought the car from.. yep, he aint gonna live this down anytime soon..), tried to account for mitsu using white as signal, black as earth (where as the sensors usually use black for signal, white for earth), but switching the wires around when he wired in the new sensor.. but didn't realise that the plug where it plugs into the loom switches the wires for you...

re-soldered teh wires coming out of the O2 sensor the correct way around, and it's all working great! looking forward to seeing a difference in fuel economy!
Ok, I'll ask the question...whats the correct wiring ??
I have recently *cough* replaced the O2 sensor - now you have me worried !!!
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Old 28-05-10
Rendrag Rendrag is offline
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Quote:
Originally Posted by Commandant View Post
Ok, I'll ask the question...whats the correct wiring ??
I have recently *cough* replaced the O2 sensor - now you have me worried !!!
*grin* Depends on how you 'replaced' it If you bought a mitsu replacement, screwed it into the exhaust, and plugged it into the loom, you should be all good...

If you bought a 'generic' bosch sensor, and cut the old sensor off its cable, and soldered/crimped the wires together, then it's worth checking...

On the *car* side of the plug/socket into the loom, signal is white wire, ground is black wire.. However that gets flipped around in the plug/socket (because the bosch standard is black wire is signal), so you want to make sure you put the sensor's signal wire to the BLACK wire, and its ground wire to the GREY wire..

In my case, that meant the purple wire from the sensor went to the black wire to the plug, and the 'light brown' wire (looked more like pink to me) goes to the grey wire to the plug..

These two sites were quite a bit of help:

http://www.vaglinks.com/VAGLinks_Com...orInstall2.pdf

and

http://www.lambdasensor.com/main/mcolours.htm

Although it was changing multimeters to one which has a much larger '-' display that made me realise it was back to front! - with the ECU disconnected and the engine warm, it was reading -240mV, which made me twig that it was wired backwards With the ECU in, as I think I said earlier in this thread, it was reading -20mV

I never did find out where the green shielded wiring comes from, as it's not there where the wiring comes in under the radio in the centre console!

NOw she's running much better.. - but no idling.. sigh, got some new plugs to try, since it's likely been running super-rich!
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Old 28-05-10
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Quote:
Originally Posted by Rendrag View Post
*grin* Depends on how you 'replaced' it If you bought a mitsu replacement, screwed it into the exhaust, and plugged it into the loom, you should be all good...

If you bought a 'generic' bosch sensor, and cut the old sensor off its cable, and soldered/crimped the wires together, then it's worth checking...

On the *car* side of the plug/socket into the loom, signal is white wire, ground is black wire.. However that gets flipped around in the plug/socket (because the bosch standard is black wire is signal), so you want to make sure you put the sensor's signal wire to the BLACK wire, and its ground wire to the GREY wire..

In my case, that meant the purple wire from the sensor went to the black wire to the plug, and the 'light brown' wire (looked more like pink to me) goes to the grey wire to the plug..

These two sites were quite a bit of help:

http://www.vaglinks.com/VAGLinks_Com...orInstall2.pdf

and

http://www.lambdasensor.com/main/mcolours.htm

Although it was changing multimeters to one which has a much larger '-' display that made me realise it was back to front! - with the ECU disconnected and the engine warm, it was reading -240mV, which made me twig that it was wired backwards With the ECU in, as I think I said earlier in this thread, it was reading -20mV

I never did find out where the green shielded wiring comes from, as it's not there where the wiring comes in under the radio in the centre console!

NOw she's running much better.. - but no idling.. sigh, got some new plugs to try, since it's likely been running super-rich!
Oh Shite.
Yep. I replaced with the no frills Bosch one. I had better jump underneath this weekend and have a look.
Many thanks for the heads up post.
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Old 28-05-10
Rendrag Rendrag is offline
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Quote:
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Oh Shite.
Yep. I replaced with the no frills Bosch one. I had better jump underneath this weekend and have a look.
Many thanks for the heads up post.
What might be easier if you've got a multimeter handy, is wait till the car's warm, then pull the passenger kick panel off to get at the ECU, and shove the positive lead of the multimeter into the white wire (pin 4) of the largest plug (closest to the firewall), with the negative lead connected to ground (case of the ECU worked for me ) - if you get about 0.2V or so, she's all good.. if she's negative by a few mV or zero (depends on how sensitive your multimeter is ), then it's around the wrong way

Cheers,

Damien
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