Emissions failing - The latest test readings - Nightmare car

[markstevieandmads]

Oscilliscope is actually better then analgue.

Theres an issue either with the sensor or the wiring. Your making this more complicated than it is.

[Mr2Owner]

I stuck the old sensor back in today and my mechanic tested it on emissions again and it passed, Co was 0.06 at one stage and lambda was pretty much bang on.

I think there is an intermittent issue, one minute the emissons are ok the next there not.

I tried testing this old sensor today after refitting it, I didn't get any oscillations and when I unbridged TE1 and E1 as autodata states and then check for voltage at Vf1 and E1 I got 2.25volts with a digital meter. Autodat states if volts is over 0v to replace sensor. Yet the car then went and passed emissions on the mechanics emissions machine so whats going on.

[SonicSW20]

VF1 is fuel trim, you won't see oscillations on that. OX1 gives the raw signal from the lambda sensor.

EDIT: incorrect, see posts below.

[Mr2Owner]

VF1 is fuel trim, you won't see oscillations on that. OX1 gives the raw signal from the lambda sensor.

Well the Toyots manual states to bridge TE1 and E1 with a paper clip etc.
Then whilst they are bridged, rev the engine to 2500rpm to warm it and then put the analogue meter probes on E1 and VF1 and it should oscillate about 6 times in 10 seconds.


Now you're saying not to use Vf1 So, am I correct in saying there seems to be a misprint or typo in the Toyota and Auto data instructions as I suggested in my original post. AS both those sources state VF1.

[Mr2Owner]

VF1 is fuel trim, you won't see oscillations on that. OX1 gives the raw signal from the lambda sensor.

This car just failed the actual national car test emissions again today, despite being perfect 2 days ago on my mechanics emissions machine.

I think there is an intermittent wiring issue with the Lambda sensor, I really need to know how to check the sensors wiring.

@Gazza - Can you describe to me the procedure you are using to test the sensor oscillations. Are you leaving TE1 + E1 bridged together with a paper clip whilst you then test the other 2 terminals for the oscillations? Or are you just testing the 2 terminals for oscillations whilst T1 + TE1 are not bridged?

And are you using a digital multimeter or an analogue one?

[Mr2Owner]

I tested the Lambda sensor now regards the following tests:

- Continuity between the 2 black heater element wires of the sensor itself = Have continuity and 05.5ohms.

- 12v at the heater wire on the car loom side with key on = Have 12v

[Mr2Owner]

Does anyone know what the 4 wires of the Lambda sensor on the car loom side are? I know the black wire is the heater 12v supply. 1 of them has to be the ground back to the Ecu for the heater and I can probably figure which one it is by seeing which terminal the other black wire on the sensor goes to in the plug but if someone knows offhand all the better as I've the car put away for the evening.

Black = heater 12V
Brown = ?
Red / White = ?
Blue / Yellow = ?

[markstevieandmads]

I wouldnt worry bout what they are but be checking continuity from one end (from the lamda plug) to the other (whereever it goes - havent got wiring diagrams to hand).
Also bend them about while checking to check for breaks.

[SonicSW20]

VF1 is fuel trim, you won't see oscillations on that. OX1 gives the raw signal from the lambda sensor.

Well the Toyots manual states to bridge TE1 and E1 with a paper clip etc.
Then whilst they are bridged, rev the engine to 2500rpm to warm it and then put the analogue meter probes on E1 and VF1 and it should oscillate about 6 times in 10 seconds.


Now you're saying not to use Vf1 So, am I correct in saying there seems to be a misprint or typo in the Toyota and Auto data instructions as I suggested in my original post. AS both those sources state VF1.

I was wrong, just tested on my own car. E1 - OX1 gives the raw signal from the O2 sensor. E1 - VF1 in diag mode will switch between 0 and 5V. If you don't put it in diag mode, it give you the fuel trim which should be around 2.5V. This is different to the signal from the O2 sensor on OX1 as this the feedback from VF1 has been processed by the ECU.

Just uploading some videos from mine to YouTube now for you. It's a '99 UK NA, but it's the same diag system.

[SonicSW20]

E1 - OX1, not in diag mode (don't think it matters) - https://www.youtube.com/watch?v=A-VBpBqPFiE

E1 - VF1 in diag mode - https://www.youtube.com/watch?v=TsqcKiNnqIw

Ef - VF1, not in diag mode - https://www.youtube.com/watch?v=lwXTR1qMoEg

[Mr2Owner]

VF1 is fuel trim, you won't see oscillations on that. OX1 gives the raw signal from the lambda sensor.

Well the Toyots manual states to bridge TE1 and E1 with a paper clip etc.
Then whilst they are bridged, rev the engine to 2500rpm to warm it and then put the analogue meter probes on E1 and VF1 and it should oscillate about 6 times in 10 seconds.


Now you're saying not to use Vf1 So, am I correct in saying there seems to be a misprint or typo in the Toyota and Auto data instructions as I suggested in my original post. AS both those sources state VF1.

I was wrong, just tested on my own car. E1 - OX1 gives the raw signal from the O2 sensor. E1 - VF1 in diag mode will switch between 0 and 5V. If you don't put it in diag mode, it give you the fuel trim which should be around 2.5V. This is different to the signal from the O2 sensor on OX1 as this the feedback from VF1 has been processed by the ECU.

Just uploading some videos from mine to YouTube now for you. It's a '99 UK NA, but it's the same diag system.

Wow, where were you 2 months ago Cheers for all that info dude, really clears up the way the whole O2 sensor works for me. Thanks for taking the time to put up them videos, I appreciate that. Good to have confirmation I was bridging it correctly, etc..

The last time I tried checking it I remember getting 2.25V when not in diag mode which appears to be ok with your 2.50V. I can't remember what voltage I got in diag mode, i used an analogue meter and couldn't see it fluctuating and didn't remember the volts.. I'll try it again with my digital multimeter. Its funny though, with TE1 + E1 bridged I can't recall it going into diag mode and raising the revs the way it did the other times I tested it, maybe I didn't make a good connection, although the engine management light was flashing so it must have connected, I'll have to double check these tests again and post back.

I didn't know about the E1 - OX1 being the raw signal, I'll check that out too and see how it compares.

Just 1 question, am I correct in thinking if I back probe the signal wire at the lambda sensor to car loom plug, I should see it switching between 0 - 5v? Or should I see the static 2.50V? I'll check and post back my findings, I'll look through the diagrams too and try trace the wires back to the Ecu and check for continuity.

[tottacrolla]

If it were a 5 wire wideband sensor then 0 - 5v would be correct for an Ox reading. Given that the 4 wire sensor is narrowband I think that the test as above may only be checking the heater circuit.
The narrowband sensor oscillates between 0.1v and 0.9v approx centering on 0.45v at stoich. The sensor creates its own voltage. Some ecu's are calibrated to go open loop (no O2 sensor input) at idle and full throttle. (Usually single wire sensor, no cat)
If there is a problem with the heater circuit you would likely see fluctuations with the O2 readings as the sensor relies entirely on exhaust temp.

[SonicSW20]

If it were a 5 wire wideband sensor then 0 - 5v would be correct for an Ox reading. Given that the 4 wire sensor is narrowband I think that the test as above may only be checking the heater circuit.

The signal at VF1 is not the heater circuit. It's the feedback from the ECU after it's processed the signal from the O2 sensor. It'll only fluctuate when the engine is operating in closed loop mode.

http://mr2wiki.com/MKI/OxygenSensorAnalysis

[tottacrolla]

If it were a 5 wire wideband sensor then 0 - 5v would be correct for an Ox reading. Given that the 4 wire sensor is narrowband I think that the test as above may only be checking the heater circuit.

The signal at VF1 is not the heater circuit. It's the feedback from the ECU after it's processed the signal from the O2 sensor. It'll only fluctuate when the engine is operating in closed loop mode.

http://mr2wiki.com/MKI/OxygenSensorAnalysis

That is interesting, I have a Freedom ecu on the Corolla that can be set to flash the engine management light as the O2 sensor goes rich to lean. Probably a similar circuit.
The test appears to show the ecu going open loop at idle. I wonder if that is the case if the OP's issue could be that his engine is running closed loop idle ?

[Mr2Owner]

E1 - OX1, not in diag mode (don't think it matters) - https://www.youtube.com/watch?v=A-VBpBqPFiE

E1 - VF1 in diag mode - https://www.youtube.com/watch?v=TsqcKiNnqIw

Ef - VF1, not in diag mode - https://www.youtube.com/watch?v=lwXTR1qMoEg

I got some time to check my diag port readings today, here's the results:

E1 - OX1, not in diag mode = idles 0.8v and 0.1v, when revved goes to 0.8

E1 - VF1 2.25v, when i drop the revs it takes about 15secs for my multimeter to drop from 2.25 down to 0.08v.

E1 - VF1 in diag mode = 0.08v ideling, goes up to 5v when revved and stays at 5v. It doesn't fluctuate between 0 and 5v like in your video. Also, i notice when your car is ideling it was at 5v, whereas mine is at the 0.08v ideling.

From these results is my multimeter refresh rate too slow or is there a problems

[Mr2Owner]

Here's the multimeter I'm using, it seems decent enough, you'd imagine its refresh reate would be ok to show the oscilations of 0v - 5v like Gazza-Dj's multimeter in the video. I'm going to try my multimeter on another persons car to see if it will show the switching on that so I can determine if my multimeter is up to the task.

I've also determined the heater wires on the car loom side to be:
Black / yellow = heater 12v
Red / white = heater ground
Blue / yellow = ?
Brown = ?
I'm going to try find all these wires back at the Ecu and check for continuity.

But I think the main thing to establish is why my Vf1 - E1 in diag mode isn't oscilating between 0 - 5v like Gazza-Djs. Either its my multimeters inadequate refresh rate or dodgey wiring.

[SonicSW20]

Getting 0V at idle indicates an issue. Have a look at RM396E here http://www.mr2oc.co.uk/forums/198/80372.html
It's the Rev3 NA manual, however the Turbo manual is a supplement to the NA one - it only covers the things that are different.

Follow the flow chart on EG-286 - that'll tell you if the problem lies with the o2 sensor or somewhere else. If it's somewhere else then you have something causing a rich condition, which can be tricky to narrow down.

What have you checked / replaced so far?

[Mr2Owner]

Getting 0V at idle indicates an issue. Have a look at RM396E here http://www.mr2oc.co.uk/forums/198/80372.html
It's the Rev3 NA manual, however the Turbo manual is a supplement to the NA one - it only covers the things that are different.

Follow the flow chart on EG-286 - that'll tell you if the problem lies with the o2 sensor or somewhere else. If it's somewhere else then you have something causing a rich condition, which can be tricky to narrow down.

What have you checked / replaced so far?

Cheers for the link, I'll have a look through that now. I'll just point out that the car is actually going into Diag Mode when I bridge TE1 and E1, the revs lower down. I thought it raised the revs before but couldn't remember as it was a while since I had done that, but having checked again it does actually lower my revs when I bridge them terminals.

Regards what have I done so far, replaced/checked the following:
New Toyota spark plugs
New fuel filter
New Toyota cat
New Toyota Lambda sensor and a Spurious sensor, spurious is in at the minute.
New Toyota coolant sensor
Changed oil and filter
Mechanic cleaned throttle body, checked for vacum leaks, exhaust leaks, fixed minor exhaust leak which only emerged after he fitted the cat so wasn't / isn't the original problem.
I aslo put the car back to standard to help troubleshoot and make things easier, involved fitting standard air filter setup and turbo blow off valve.

[tottacrolla]

If you ever want to check diagnostic mode is enabled just press the throttle when in diagnostic mode and it should show code 51 while the pedal is pressed.

[Mr2Owner]

E1 - OX1, not in diag mode (don't think it matters) - https://www.youtube.com/watch?v=A-VBpBqPFiE

E1 - VF1 in diag mode - https://www.youtube.com/watch?v=TsqcKiNnqIw

Ef - VF1, not in diag mode - https://www.youtube.com/watch?v=lwXTR1qMoEg

Hey Tottacorola - In your video of EF - VF1 not in diag mode, your reading is 2.5v. Can you confirm that is with the engine just ticking over? If so, when you rev and hold the engine at 2500rpm does the voltage then go up to 5v?