94 camry transmission sensor issues

[dakota1205]

I have a 94 camry 3.0 liter SE model with auto o/d transmission;The problem I am having is the transmission wants to not stay in o/d, it wants to shift back down to lower gear, here lately it won't go into overdrive, so it shifts to drive (3rdgear) and stays there, then will shift back down to 2nd gear and back and forth. The o/d switch is selected for o/d. The check engine light is on. I did take to the toyota dealer last week and they checked the codes (since the local auto parts stores can't check for free with their scanners). Dealer Found 3 codes; 1st was "vehicle speed sensor", 2nd was "transmission output speed sensor" and 3rd was " O2 sensor, bank 1 sensor 1" which the service tech told me it was the one by the firewall. They wanted to charge me ~ $850 dollars to repair. Myself, being mechinically inclined, told them I will replace myself. I know I will have to replace the O2 sensor. The Hanes manual talks about the "vehicle speed sensor", but not the "transmission output speed sensor".

My question is, anyone have any knowelge on which speed sensor I should try first. And if the transmission sensor, where would it be located?

Thanks

[Mike Gerber]

Download the generation 3 Toyota factory service manual stickied at the top of this forum's home page. It is actually a 94 manual. It should have all the information you need. Here's the link:

http://www.automotiveforums.com/vbul...d.php?t=497839

Mike

[Brian R.]

Try the engine coolant temperature sensor, first. It will screw up your mixture and cause shifting issues like you describe at the same time when malfunctioning. Also, it will not throw a code. This may be the only sensor you need to change.

[chvyl01]

the transmission output speed sensor...is located on the top of the trans axle...it takes a 10 mm socket to remove one bolt the sensor has a rubber "O" ring on it and may need some coaxing to get out just keep wiggling it...it will come out....but before you remove this sensor there is another sensor that send a signal to the ECU and the combined sensors along with the gear shift selector and position of the overdrive button all combined that tell the ECU to let the transmission to shift into overdrive...here is a quick break down as to what to look for....when you drive the vehicle does the speedometer work? does it show the correct speed? if so then the speed sensor on the trans axle is NOT your problem...when you drive the vehicle does it shift from 1st to 2nd and 3rd like it should? try both of these tests with ECT button powered up and with it off...is there any difference?....now try both of these tests with the overdrive turned on and with it turned off...any difference?....if the car drives as it should in all tests except that it will not shift into overdrive ...open your hood ..look straight down on top of the transmission next to the starter...you will see a sensor there...this sensor is called the torque converter speed sensor...it has a couple different names....sometimes called a lock up converter sensor and sometimes its called an output speed sensor....this sensor determines the speed of the torque converter...sends a signal to the ECU and at a certain point the ECU will allow the transmission to shift into overdrive....if your transmission is "bouncing" back and forth between overdrive and 3rd and will not stay in overdrive I would say THIS is the sensor you need to replace....but wait......your haynes manual tells you how to check this sensor....oh yea...it's magnetic too...I promise ...this is your culprit. but before you replace the sensor...check the wiring and connectors....you may find a burned or broken wire and save yourself some$$$....Good luck [email protected]

[chvyl01]

oh by the way...half the repair is knowing how to interpret the stinking codes. you dont just look at the codes it shows...you also have to look for what codes it doesnt show...for instance....code p0753 says shift solenoid A circuit, electrical.....this doesnt mean the solenoid is bad...it means the circuit has an issue...the trick is to test the entire circuit...your o2 sensor...bamk one sensor one...is the one closest to you when you pop the hood...look straight down...there is is...how I know this...I just replaced one in a 94 Camry...I actually have the sensor I told you about "torque converter speed sensor" if your close enough or if you want to pay shipping I will give it to you. [email protected]

[dakota1205]

Originally Posted by chvyl01

the transmission output speed sensor...is located on the top of the trans axle...it takes a 10 mm socket to remove one bolt the sensor has a rubber "O" ring on it and may need some coaxing to get out just keep wiggling it...it will come out....but before you remove this sensor there is another sensor that send a signal to the ECU and the combined sensors along with the gear shift selector and position of the overdrive button all combined that tell the ECU to let the transmission to shift into overdrive...here is a quick break down as to what to look for....when you drive the vehicle does the speedometer work? does it show the correct speed? if so then the speed sensor on the trans axle is NOT your problem...when you drive the vehicle does it shift from 1st to 2nd and 3rd like it should? try both of these tests with ECT button powered up and with it off...is there any difference?....now try both of these tests with the overdrive turned on and with it turned off...any difference?....if the car drives as it should in all tests except that it will not shift into overdrive ...open your hood ..look straight down on top of the transmission next to the starter...you will see a sensor there...this sensor is called the torque converter speed sensor...it has a couple different names....sometimes called a lock up converter sensor and sometimes its called an output speed sensor....this sensor determines the speed of the torque converter...sends a signal to the ECU and at a certain point the ECU will allow the transmission to shift into overdrive....if your transmission is "bouncing" back and forth between overdrive and 3rd and will not stay in overdrive I would say THIS is the sensor you need to replace....but wait......your haynes manual tells you how to check this sensor....oh yea...it's magnetic too...I promise ...this is your culprit. but before you replace the sensor...check the wiring and connectors....you may find a burned or broken wire and save yourself some$$$....Good luck [email protected]

speedometer works fine and appears to show correct speed. It does shift to 2nd and 3rd fine with the ECT button in either position. With the O/D button; it shifts fine also, just that it won't go into overdrive. At times, it will shift from 3rd back down to 2nd if your going say ~35 mph. Are saying the torque converter sensor is the same as the vehicle speed sensor?

[dakota1205]

Originally Posted by chvyl01

oh by the way...half the repair is knowing how to interpret the stinking codes. you dont just look at the codes it shows...you also have to look for what codes it doesnt show...for instance....code p0753 says shift solenoid A circuit, electrical.....this doesnt mean the solenoid is bad...it means the circuit has an issue...the trick is to test the entire circuit...your o2 sensor...bamk one sensor one...is the one closest to you when you pop the hood...look straight down...there is is...how I know this...I just replaced one in a 94 Camry...I actually have the sensor I told you about "torque converter speed sensor" if your close enough or if you want to pay shipping I will give it to you. [email protected]

when I took the car to the dealer; the tech told me bank 1 sensor 1 was the one by the firewall. are you saying its the one you can see in the front of the engine. the manual shows both O2 sensors, but doesn't reference side of engine. I might take you up on the speed sensor if I can figure out it that is my problem.

Thanks

[Brian R.]

Bank 1 Sensor 1 is next to the firewall, not at the front of the engine.

See here

Also, for a lot of sensor and general information see this post in the FAQ thread.

PS chvyl01 may very well be spot on with his assessment of your problem, but I suggest you test the resistance of the engine coolant temperature sensor at operating temperature before you go further. It is easy and fast and is one possible source of the problems you have.

[dakota1205]

Originally Posted by Brian R.

Bank 1 Sensor 1 is next to the firewall, not at the front of the engine.

See here

Also, for a lot of sensor and general information see this post in the FAQ thread.

PS dakota1205 may very well be spot on with his assessment of your problem, but I suggest you test the resistance of the engine coolant temperature sensor at operating temperature before you go further. It is easy and fast and is one possible source of the problems you have.

I checked the resistance of the coolant sensor, it was reading about 1200 ohms and slowely increasing (due to cooling, I believe). Hopefully this is working correctly. Well find out soon. I had no resistance reading on sensor by the firewall. So i am in the process of replacing it. My other sensor was reading approx. 9 ohms, hopefully it is ok.

I keep you posted, Thanks for all the info so far.

Thanks

[Brian R.]

Unfortunately, I can't find a reference for the resistance specification for your ECT sensor. The manual says to use the output as measured by a tester connected to the ECM. The specification is in temperature readout, not resistance.

Good luck. Sounds like you've found at least one bad sensor. Be careful to get the correct sensor. Get the part number from Toyota with your VIN, even if you don't end up buying a sensor from them.

[dakota1205]

Well I put my new O2 sensor in, took off my vehicle speed sensor and cleaned it up, it had oil inside where that little ball meets the contact point, and also took off the transmission output speed sensor and cleaned it. Put it back together and still get "check engine light" (I was hoping maybe just inspecting and cleaning would solve my problem, guess not).
Transmission still shifts fine just won't go into O/D, and still downshifts from 3rd to 2nd. Don't have a tester to see if my O2 sensor is clear.

Well I guess I'm going to have to invest in sensors. chvyl01 I guess I will take you up on that sensor offer if it still stands. email me at [email protected] and we can discuss shipping.

Any info from anyone on what kind of testing that can be done on the 2 sensors on what they should read?

Thanks again guys for all the info so far.

[Brian R.]

Have you downloaded the '94 service manual from the sticky post at the top of this forum? Usually, they have information on how to check sensor function.

[dakota1205]

My camry is still acting up. Sensors checked out OK. I read somewhere about checking the ECU unit. So by opening it up and looking at it, it appears that i have 2 capacitors that are leaking some discharge from them. Could this be my problem? Does these affect my not going into overdrive and downshifting problems?

Anyone have any knowledge of this?

[kevinb70]

I know electronics/circuits, but not ECMs

if those caps are used in frequency counting/measurement/comparison, most definitely!

Resistor/Capacitor combinations are a vital part in many kinds of frequency measuring circuits.

if you can read the cap values, they can be soldered out, and new ones soldered in, if you are up for that kind of work. one hitch <possibly> would be needing to be the exact same capacticance or else the computer may say 55mph when you are actually going 48mph. might be a trimmer cap or potentiometer in there to adjust to fine tune the reading.....

this is just general timing circuit knowledge... actual design of the ECM/PCM may differ


what size are the caps? are these < 1 microfarads? 1µF? Generally the small ones are used in frequency circuits... also anything in picofarads (pF) ... but these are usually ceramic which rarely leak, compared to the barrel type electrolytic ones which can leak or pop.... the barrel type have a flat bottom with tiny vents that look like dots

[dakota1205]

I replaced the 2 leaking/bad capacitors in my ECU. The car does not downshift anymore,my check engine light is out. Seems to be running pretty good. Now the only problem is, it won't shift into OVERDRIVE. I can select the O/D button and the light will come on. It doesn't flash any more like before. I can deselect, the light will go out, and it still won't go into overdrive. Any suggestions on what may be my problem now.