morning all,

as the title sais really. not 100% sure what happens when the lambda fails and what indication you would have of this on a day to day basis. so if anybody could enlighten me that would be great.

thanks in advance

If it fails so that ecu can detect failure (ie. 4 wire ones, unplugged) the ecu runs stock maps. And you you get a good 14.7:1 at idle.

Normally however general fuel consumption ends up worse. As closed loop running works upto around 70 ish mph on light engine loads. Stock fuel map by 70 won't be mapped for 14.7 : 1

The bgb tells you how to test it.


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Darryl

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Darryl

good description thanks, a tad technical for me, what is bgb?

GB = Big Green Book = Toyota Workshop manuals
Some of them are available on the Swiss GT4 drivers club in the information area
Http://www.gtfour.ch

The diagnosis procedure just needs a volt meter. My simple procedure :-
From cold...
Connect voltmeter between OX and E1 terminals in diagnostic connector - ground to E1
Turn on ignition
Meter should read ~ 0V
Start engine
Meter should quickly change to read 0.8 - 0.9 V
Allow engine to idle
After a couple of minutes you should see the meter reading drop quite quickly to 0.5 V and you should hear the rpm drop as the car comes off the "choke"
The meter reading should then swing about in the 0.4 - 0.6V range

The O2 sensor reads 0V to indicate lean, 0.5V to indicate stoich and 1V to indicate rich
Typically when the sensors fail they read fully lean all the time so if you go through the above test and the meter reads low during warmup the sensor has failed

thats great cheers, dont have a dignostic connector, so ill take it off and test it does anybody know which wires are which, 2 black 1 white 1 blue, not sure which is the signal and return?#

cheers

The diagnostic connector is on your car - rear RHS of the engine bay between the suspension turret and the bulkhead.

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GT4DC Events Co-ordinator
1996 ST205 UK

excellant, thanks for that

firstly id like to thank those who answered you saved me a lot of time so very greatful.

I tested the sensor as described and the followuing happened,

connected turned on ignition volt reading zero,
started engine and it probably took about a minute and the reading went up steadily to 0.9 volts and held
left the engine to run a few minutes the reading started to drop but it got to 0.6 and then jumped back up to 0.9 then dropped jumped back to 0.8 so averaging it i would say it was reading between 0.6 and 0.8 when warm which is higher than stated.

so my questions for those on the know

1, does this mean the sensor is knackered?
2, what will happen if i run the car with this sensor like this?
3, in this state would this cause the cat to overheat when driving hard?
4, what difference would it make if i changed it, i.e running smooth etc?

again thanks but fuel system ecu etc are beyond my knolwedge

Those readings aren't right. It's either really running rich or the sensor is forked

You could try giving the sensor a clean with a lemon. Not something I have tried but if you Google o2 sensor clean lots of people claim good results

If the sensor is bad the car is potentially in a dangerous place. The ecu will be reducing fuel due to the rich reading so the engine might actually be running a bit lean

If the clean process doesn't work you've got a couple of options
1. Replace sensor
2. Find a friendly MOT place and check emissions to see if it's really running rich or lean

Genuine sensors are >£100 so if you can swing a basic emissions test for a donation to the biscuit fund it might be worthwhile

I've done the lemon thing, and its safe to do, cleans the sensor well. Didn't alter anything in my case but I didn't have troubles before cleaning it.

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Darryl

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Darryl

I put mine in vinegar over night, and it seemed to bring it back to healthier condition.

I also tried it with my O2 sensor...

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ive cleaned the sensor a few times with lemon generally before its mot, as for mot ive been fortunate with where i take it, so emmisions isnt a problem the confusing bit for me now, is this sensor the cause of it running rich or is it likely to be another fault and the sensor reading correct ive spent a few hundred recently replacing parts that didnt need replacing and as the car sits in the garage most of the year am getting rather dissheartened with it

Problem is by skipping the emissions test you don't pick up genuine issues

It sounds like you are on good terms with the tester. Ask him if he can stick his probe up your tailpipe one lunchtime lol. You only need a lambda for natural idle but fast idle might be a bonus
If the tester idle values are weak or dead on the sensor is duff. If they are rich the issue is elsewhere - possibly coolant temperature sensor

cheers, the responses are much appreciated. i guess this is not goinmgto as simple as i thought!

A bit tardy but here you go
Healthy looking readings at idle

https://www.youtube.com/watch?v=9WYpXH6SSuo