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Intermittent Lean Condition - BPU TT6 - Urgent Help Needed!! - Update


Samurai 20V
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Hi guys..

 

Referring my previous thread, this is the current situation with my car.

 

http://www.mkivsupra.net/vbb/showthread.php?258411-Supra-Running-Lean!!-Error-Code-21-HELP!!

 

 

I have the Mines ECU and a brand new Bosch O2 sensor fitted.

 

The car is showing error code 21, Main Oxygen sensor. Even after clearing the codes on the ECU, turning the key to ON in diagnostics mode, the 21 error code comes thru almost immediately...

 

It drives as follows;

 

- Cold start, AFR - 11. Then warms up after about 2 minutes AFR reads 14.7 - 15.2

- Normal operating temp (Oil at 90deg plus, water temp at halfway) - Idle AFR is 14.7 - 15.0. Full throttle sees low 10's and 11's.

- Car feels very nice, smooth, responsive and WOT the accelaration is immense.

 

Today I used the car to work, this happened;

 

- At a cruise on the highway, AFR went lean, off the gauge. Car was in 3rd and 4th gear,2000rpms, flat road, 10% throttle or lower.

- I pulled off, switched the car off, started it up again and AFR went lean off the scale.

- I had to nurse the car to work, AFR showing lean most of the time. Sometimes the car started hunting at idle.

- In the parking lot, idled for 10mins, AFR was perfect, 14.7 - 15.2.

 

So I am highly confused at to what is the issue, these are my questions.

 

1. Would I have caused any damage driving the car in that lean state?

2. I am intending to check the ECU plug to confirm the O2 sensor wire is intact. If the wiring checks out, what is my next action?

3. I have the stock ECU in the car, should I fit this and drive the car home? There was no error code with this ECU (this was using the old O2 sensor though).

4. Is there any anything I am missing here?

 

Please help!

Edited by Samurai 20V (see edit history)
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as scott says mate if the o2 is the only thing you have changed then it must be that. simple way to see is plug the old ecu back in for your trip home and see if it goes lean again.

 

going of scale lean can cause damage but if it was on cruise and idle you should be okay its when you are lean wide open throttle you want to worry

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Old ECU with old O2 Sensor - OK

New ECU with old O2 Sensor - OK

New ECU with new O2 Sensor - Fubarred

 

From that my first guess would be that the O2 sensor is a duffer.

 

 

as scott says mate if the o2 is the only thing you have changed then it must be that. simple way to see is plug the old ecu back in for your trip home and see if it goes lean again.

 

going of scale lean can cause damage but if it was on cruise and idle you should be okay its when you are lean wide open throttle you want to worry

 

Old ECU with new sensor = OK..

 

The new sensor metered exactly the same with the old ECU connected.

 

If it ran really rich before you fixed the wire you talked about i would take out the sparkplugs as they dont like running rich. And go from there. A bad spark plug puts afr all over the scale.

 

 

You may be right there mate, it did go mega rich, I have an old set of plugs that were working fine will swap them out..

Edited by Samurai 20V (see edit history)
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Nope, it worked with your old sensor and your old sensor worked with your stock ECU so there is no way the sensor was wideband.

 

Well, you are right. The car only started all this crap after the boost pressure wire pull off, before that it worked fine.. Could that have damaged the ECU in anyway?

 

Not sure what to do next, when the Mines is running properly the car feels so much better so I want to get it working properly again..

 

The car is running fine at the moment with the stock ECU and new sensor..

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I would double check the wiring where the boost wire was pulled out. Other areas may have been tugged on at the same time, but not came out fully.

 

Thanks mate..Will have to check that out..

 

The previous owner did make a mess of the wiring, he had all sorts of gizmos running there..

 

I took a day off this week, will sort the wiring out, then put the Mines ECU back in and check the behavior...

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have you tried plugging the mines back in again just to prove the ecu it could even be a bad conection on a pin or something

 

Pins look fine from the outside.. I will run the car again tomorrow with the stock ECU, check out the wiring, make sure that is spot on ,then plug the Mines back in and see what happens..

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Not really sure what you are asking here.

 

You have a non-vvti, the ECU is for a non-vvti? The VVTi ECU is different from the non-vvti, they cannot be swapped.

 

 

The ECU was working fine... the sensor was working fine.... a wire got pulled and now it's not working. I would personally concentrate on that instead of trying to find issues that aren't there.

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I did for all times, except tonight, was in a rush and forgot about it..

 

Cant remember if I did for the first time I swapped them over though..

 

Is it a major issue if not?

 

Might be, might not be. Not really sure it's just standard practice as far as I am aware. I've read that the ECUs are fairly robust so it should be OK, I would always make a point of not connecting an ECU to a live contact by hand. It means some pins will make while others won't, it won't be plugged in uniformly which can be bad for electrical items.

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Not really sure what you are asking here.

 

You have a non-vvti, the ECU is for a non-vvti? The VVTi ECU is different from the non-vvti, they cannot be swapped.

 

 

The ECU was working fine... the sensor was working fine.... a wire got pulled and now it's not working. I would personally concentrate on that instead of trying to find issues that aren't there.

 

Yes, the ECU is from a non-VVTi, my car is non-VVTi.. I get your point, I am running away with my thoughts here..

 

Might be, might not be. Not really sure it's just standard practice as far as I am aware. I've read that the ECUs are fairly robust so it should be OK, I would always make a point of not connecting an ECU to a live contact by hand. It means some pins will make while others won't, it won't be plugged in uniformly which can be bad for electrical items.

 

Point noted, will make sure the battery is disconnected in future swaps..

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Update from this mornings drive to work with old ECU and new sensor.

 

Car was perfect, AFRs never went above 15.2.

 

However O2 sensor meters between 0.08V and 0.75V, although there is no error code.

 

Next action is to check out the wiring, change the spark plugs, fit the Mines and see what happens..

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so what your saying is there was no problem with the drive in but you are still trying to find one?

 

if you are trying to pin point a fault it is best to change one thing at atime so you know what is wrong,

 

so you say the stock ecu is fine yes so then plug the mines in and see if the fault comes back if it does then i would say you blew something when you changed ecu's with the battery conected. if the mine is fine as well then i would of said it was a bad conection.

 

just my veiw you dont have to listen of corse

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so what your saying is there was no problem with the drive in but you are still trying to find one?

 

if you are trying to pin point a fault it is best to change one thing at atime so you know what is wrong,

 

so you say the stock ecu is fine yes so then plug the mines in and see if the fault comes back if it does then i would say you blew something when you changed ecu's with the battery conected. if the mine is fine as well then i would of said it was a bad conection.

 

just my veiw you dont have to listen of corse

 

I am trying to locate the problem with the Mines ECU. You are right, one item at a time is the only way to trouble shoot.

 

The sensor was changed because of the code 21 and incorrect voltage.

 

Then all the issues with running lean occured..

 

To troubleshoot I am gonna change the plugs first, make sure they are ok.

 

Then I am gonna check the wiring to make sure there are no loose contacts..

 

If the Mines ECU still shows a fault then its most like messed up from when I installed it the first time..

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Ok, here is the latest..

 

Changed the plugs to a working set that I had just to make sure.. Car ran fine..

 

Unplugged the ECU harness, checked for any signs of bad wires, nothing visible...

 

Plugged in the Mines ECU, turned the key to ON in diagnostics mode, no error code code!!

 

Then started the car, error code returned..

 

AFR was fine though, it did go lean once on idle but it returned to normal pretty quickly. Drove around on a cruise, AFR was fine, on boost it was 11 and below.

 

O2 sensor was reading a solid 0.02V.

 

Swapped back to the stock ECU, no error code, AFR ok, 02 sensor metered - switching bet 0.08V and 0.75V...

 

I think it is most likely a wiring fault with the 02 sensor pin on the ECU harness or the Mines ECU. But based on the fact it did not get a code until started up, it could be sensor side connector as well.

 

Anyway, the car is going in for spraywork, I am going to South Africa for a month so I stuck the old ECU back in...

 

When I return I will open up the connectors on the ECU and O2 Sensor, if that does not solve the problem, then the ECU has to go to Mines.

 

ANy thoughts?

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