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Wont Shift into Overdrive

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Old 01-08-10, 11:22 AM   #1
Dirty SC
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Default Wont Shift into Overdrive

I have a 95 SC300 Automatic with about 170,000 miles i bought this car about 8 months ago

The problem started about a week ago. i noticed that while going about 50-55 mph my rpms stay at about 3000rpm when usually they would be below 2000. so the first thing i did was press the overdrive button the shifter and nothing the Overdrive light doesnt come on in the dash when it used to and it still doesnt go into overdrive. all of the other gears go in fine. no slipping no hard shifts, it downshifts smoothly.

next step i did was change the Fluid and filter in the tranny and still nothing.

the tempurature outside usually is around 80-90 degrees, but we had a cold front for the past week and outside tempuratures are around 35-50 degrees. i noticed while driving i see the tempurature gauge stay below the middle where it usually is. could it be that the person that had the car before me took off the thermostat? ive yet to check but it seems like the thermostat is either stuck open or there is no thermostat at all from just looking at the temp gauge..

i read on other forums that if the operating tempurature on the car is too low, the ECU wont let the transmission shift into overdrive so it wont put a load on the motor while it being under the operating tempurature. i dont know if this is true.


has anybody ever had this issue with there SC300s?

Could it be that my Transmission is on its way out?

I also hear it could be my ECU is going bad. i just dont know what to do.
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Old 01-08-10, 12:36 PM   #2
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could be a few things transmission shift point controled by three elements. Engine temp sensor located behind the water inlet from the rad. Also tps and ecu. it could also be a solenoid in the trans itself. The easiest thing to try is the ecu. If you can borrow a KNOWN working ecu it should solve ur problems if not give the other things a check
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Old 01-08-10, 07:26 PM   #3
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when you say ecu, you mean the main engine ecu right?
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Old 01-08-10, 09:27 PM   #4
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when you say ecu, you mean the main engine ecu right?
Yes main engine ECU controls transmission as well as climate control among other things
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Old 01-08-10, 10:23 PM   #5
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ECU for sure bro.
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Old 01-11-10, 05:29 AM   #6
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Originally Posted by YeA 2jZ View Post
could be a few things transmission shift point controled by three elements. Engine temp sensor located behind the water inlet from the rad. Also tps and ecu. it could also be a solenoid in the trans itself. The easiest thing to try is the ecu. If you can borrow a KNOWN working ecu it should solve ur problems if not give the other things a check
thanks for your help. i have been trying to find somebody locally with an ECU but i havent had any luck...i have a friend that has a 97 sc300 but i believe his is OBD II mine is OBD I and he said that his computer wont work on my car. is this true??

Is there Any SC300 owners in the West Palm Beach FL area that can let me use your ECU for a couple minutes i would greatly appreciate it.
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Old 01-11-10, 06:22 AM   #7
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Quote:
Originally Posted by Dirty SC View Post
thanks for your help. i have been trying to find somebody locally with an ECU but i havent had any luck...i have a friend that has a 97 sc300 but i believe his is OBD II mine is OBD I and he said that his computer wont work on my car. is this true??

Is there Any SC300 owners in the West Palm Beach FL area that can let me use your ECU for a couple minutes i would greatly appreciate it.
I am not quite sure if the one from a 97 would work if its OBDII then for sure it wont work. I live in near pembroke pines i dunno if you would like to drive down a bit mabey i can help you out i have a 92 auto
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Old 01-11-10, 08:16 AM   #8
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I am not quite sure if the one from a 97 would work if its OBDII then for sure it wont work. I live in near pembroke pines i dunno if you would like to drive down a bit mabey i can help you out i have a 92 auto

thanks man if i cant find anybody localy, i will definatly be sending u a PM.

pembroke pines is that exit Hollywood? i think thats like about an hour away.
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Old 01-11-10, 10:46 AM   #9
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thanks man if i cant find anybody localy, i will definatly be sending u a PM.

pembroke pines is that exit Hollywood? i think thats like about an hour away.
Yea thats the Hollywood ext if ur on I-95 but i am off the Miami Gardens Exit on I-75
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Old 03-28-10, 06:34 PM   #10
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Updates? Did the different ECU solve this issue?
(having a similar problem)
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Old 03-28-10, 11:17 PM   #11
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Updates? Did the different ECU solve this issue?
(having a similar problem)
YES ECU fixed the problem! just got an ecu last friday! and sure enough as soon as a plugged it in my car ran smoother and overdrive went in no problem!
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Old 02-23-11, 10:03 PM   #12
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YES ECU fixed the problem! just got an ecu last friday! and sure enough as soon as a plugged it in my car ran smoother and overdrive went in no problem!
so when you're going 50-55mph what are the rev.s at?
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Old 02-23-11, 10:03 PM
 
 
 
 
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2000, 3rd, 400, automobile, club, gear, lexus, overdrive, owners, problem, rx, sc, sc300, sc400, shift, thermostat, transmission, wont

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