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Old 01-03-09, 07:10 PM   #91
jgscott
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Originally Posted by OneSickSC View Post
alright i did one test run with the wire cut at the ecu(cel on) wit the car at normal operating temp....car shifted fine at redline.....but with the sensor unplugged it shifted at 5k as i stated above......so i think for us OBDII guys we might have to just cut the wire and deal with the cel on unless some can figure out how to trick the ecu.....

David
Do you know what the cel code is and reads ?
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Old 01-03-09, 08:03 PM   #92
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Hhmmmm, I see what you are saying. A resistor would probably satisfy condition b (current to solenoid) buy not condition a (duty cylce to solenoid). I'll have to check the DTC detection condition for obd2 but I'm pretty sure it's the same.

I really don't think there are any bad long term effects. Keep in mind that on an obd1 car, disconnecting the solenoid doesn't even turn a light on. Mine is still shifting good, although hard, which is what I want.

Which screws? The TPS screws? Remove them with a pair of vise grips or a pair of side cutters and pickup some new ones at the local hardware store. I'm fairly sure they are the same thread / pitch as the screws holding the MAF sensor to it's housing. They are just machine screws, nothing special.

Keep in mind, one of the main inputs to the ECU for just about everything is the engine coolant temp sensor. It has much too do with about everything, including shift schedules. Could even be an open loop / closed loop thing.

OneSick, you could try a different resistor but I have a feeling that sc-driver is on to something, the ECU may not be simply looking at amps and ohms to determine if there is a problem. Having the CEL on won't hurt anything but it can be annoying to look at. If you plan on keeping the wire cut and don't find a CEL solution, wouldn't be a bad idea to get your car scanned every once in a while to make sure you don't have codes for anything else.

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Old 01-04-09, 12:11 AM   #93
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While we'er on this. I have a question that I always wondered that you just brought up about engine temp.

If you run a lower temp thermostat, will the engine still perform at peak performance. On some cars, the ECU will not allow peak performance until the engine reaches the full set operating temp.
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Old 01-04-09, 03:04 AM   #94
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jgscott I believe the code is P0715 and it basically reads bad speed sensor. As for the lower temp thermostat, I too have wondered about this, but it should have its own thread.
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Old 01-04-09, 07:06 AM   #95
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I am using a stant thermostat which is about 10 degrees colder than stock. Can't remember the temp, I think it's 160 and stock is 170. I know the stock thermostat is already a little cooler than most stock units.

TRD makes one so I'm personally assuming that it is ok to use.

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Old 01-06-09, 05:06 PM   #96
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Quote:
Originally Posted by sc-driver View Post
jgscott I believe the code is P0715 and it basically reads bad speed sensor. As for the lower temp thermostat, I too have wondered about this, but it should have its own thread.
So now this mod works ? So if I understand this gives more low end power but no other disadvantage besides the Check engine code of speed sensor. The shifts are now ok at the proper RPM ?

Ok so where is the speed sensor ? On each wheel ? How can we get that code off and fool the ECU ?
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Old 01-06-09, 06:32 PM   #97
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Quote:
Originally Posted by jgscott View Post
So now this mod works ? So if I understand this gives more low end power but no other disadvantage besides the Check engine code of speed sensor. The shifts are now ok at the proper RPM ?

Ok so where is the speed sensor ? On each wheel ? How can we get that code off and fool the ECU ?
Its just a little bit more complicated then that.

For OBD-I vehicles (1995-):
  • Disconnecting the speed sensor from underneath the car will give you what you want, but it will make the Overdrive light on your dash light up and off a lot.
  • Cutting the wire from the ECU will not make lights on your dash come up

For OBD-II vehicles (1996+)
  • Disconnecting the speed sensor from underneath the car WILL give you a check engine light AND it seems that it will make the car shift sooner.
  • According to OneSickSC, cutting the wire from the ECU WILL still give you a check engine light BUT the shifting seems normal this way.

What the transmission does when you step on the gas peddle really hard is that it makes the tranny slip a little, reducing power to the wheels for a smoother acceleration.
Without information from the solenoid the ECU wont what would be a "smooth" acceleration so it basically just ignores it. This difference is felt when you step on it. All of the cars power will go to the wheels. Your car, in my opinion and experience will accelerate faster.

If I'm leaving anything out, or something is wrong feel free to correct me KC.\
-----------------------------

On a different note, I'm thinking of wiring a single pole double throw relay(SPDT), like t42gs3 suggested in post #17. That way i can just flip the ECT/PWR switch and have it disconnect. I would really hate looking at that CEL all the time.

Normal would then be smooth Lexus acceleration. Flip that switch and we got a quick Sports Car

David
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Old 01-07-09, 08:31 PM   #98
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sc-driver,

You pretty much summed it up. Just a couple of things to add.

For OBD1 -

Unplugging the direct clutch speed sensor will make the OD light flash on the second trip and it will flash until you plug it back in. This is very annoying.

Cutting the wire to the solenoid will not make the light flash but there will be a trans code 46 stored.

There were a couple of people who said that the trans felt like it was slipping with the direct clutch speed sensor unplugged. I did not notice this for the short time I had it unplugged.

OBD1 and 2 -

The entire purpose of the no 4 (accumulator backpressure control) solenoid is to bleed pressure off as the accumulators are filling up. This in effect gives the ECU the power to make the accumulators larger than they really are. IMO, disabling this solenoid is much the same as throwing a few shims into the accumulators, if the solenoid can't bleed pressure from them they will fill up quicker resulting in a quicker / firmer shift.

From the repair manual, this is my favorite quote :

Quote:
Originally Posted by 95 SC400 automatic transmission repair manual
3. ELECTRONIC CONTROL SYSTEM
The electronic control system for the A341E, A342E automatic transmissions provides extremely precise
control of the gear shift timing and lock-up timing in response to driving conditions as sensed by
various sensors located throughout the vehicle and in response to the engine’s running condition.
At the same time, the ECU control reduces vehicle squat when the vehicle starts out and gear shift
shock.
The electronic control system is also equipped with a self diagnosis system which diagnoses malfunctions
for the vehicle to continue functioning when a malfunction occurs.
Also sc-driver, it's not for me..but I really like the switch idea. Should work very well. Go for it!

jgscott... The speed sensor is not a wheel speed sensor, it's located right after the transmission bellhousing on the driver's side. But from what everyone is saying, you might consider going straight to cutting the solenoid wire. As far as the CEL, don't know how to fool the ECU. Need someone smarter than me to figure that out.

KC
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Old 01-08-09, 12:18 PM   #99
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yea i was thinking about just running a switch to the ecu wire and just turn off the connection when needed then just turn back on the connection(so i wont have a cel) when im done using it....but if u all figure out how to wire in into the ect switch that would be a great write up for all the OBDII people.....keep us updated guys



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Old 01-27-09, 06:06 PM   #100
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the switch thing works but after you turn it back on i still have to reset the ecu....so there has to be an easier way....
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Old 01-27-09, 07:36 PM   #101
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Quote:
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the switch thing works but after you turn it back on i still have to reset the ecu....so there has to be an easier way....
It might take 2 (or more) trips / key cycles for the light to go back off.

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Old 01-31-09, 10:28 AM   #102
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awesome work gents, I think this combined with the paddle shifter set up I have been looking at will be purrrfect. I will try this mod in a few weeks as soon as I get a few more parts that I ordered.

Thanks again and keep up the great work!
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Old 04-13-09, 01:54 PM   #103
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Old 04-13-09, 02:25 PM   #104
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Excellent thread. Definitely glad it was linked to another one today.

On my OBD-1 SC400, with the wire cut you mentioned having a trans code stored. Just for clarification's sake, this still won't contribute to any dash light, correct?
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Old 04-13-09, 02:58 PM   #105
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^ I want to know the same, also what if i ran a switch to the sensor on the bell housing, will the light immediately go away when i reconnect power?
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Old 04-13-09, 02:58 PM
 
 
 
 
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1995, 94, a340e, a342e, automatic, downshift, es300, flashing, lexus, light, od, p0715, ranger, sensor, speed, toyota, transmission

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