'93 Tacoma auto overdrive problems (2wd)

[smalltowncowboy]

Okay, I'm new and trying to help. My uncle has a '93 Tacoma 2wd auto overdrive but no computer. I get help occassionally at other forums but I do not presently own a Toyota (no sticks or stones, please). He asked for help and here we are. WE both are capable mechanics on American trucks or logging equipment but are unfamiliar with this truck. He says that it does not always shift into overdrive when cold (or was it hot?). Once that it does the truck runs fine but other times, it never goes into OD and stays in 3. He has had trans flushed twice and has proper fill amount. I asked if the trans was vacuum or electronic. He doesn't know. Other makes are computer run electronically so I am asking does the trans heve a seperate computer for trand and can codes be retrieved. If so, what type of scanner is used. I need to know what to check. He bought this truck only a few months back. He'd probably just drive it or trade it if the trans needs overhauled. I don't know yet if he has a shop manual on it. I would like some input as to what actuates the shifts and what might be possible problems/solutions. OD light will go on and off when button is pushed but does not "blick" as a Ford would with problems. I thank everyone in advance for their assistance.

[smalltowncowboy]

He said OD didn't work when cold and the truck has ~100K miles. I did a search and another post was talking about solenoids, relays, and sensors. It was in the form of a question too though and not much help. Thermostat was changed. I need to know which sensor tells the computer that the truck is warm enough for OD and which relay it would go through. I don't think it'd be servo or solenoids since OD works rest of the time. Nor would I rebuild the trans. I need to know if trans is electric and has a stand alone computer or uses another and where. I appreciate all replies, Thanks.

[robinhood150]

Sounds perfectly normal. What happens is the computer won't let the tranny shift into overdrive until the engine temperature is hot enough for the emmissions controls to start working. Toyota does this to meet emmissions requirements. This is a very well known thing in the toyota truck community (I'm not sure if the cars do it too). Usually it'll start shifting into overdrive after a couple minutes of driving, kind of annoying if driving on the freeway.

Also, the Tacoma's weren't produced until 1996 so your dad has the "pickup", no name. AKA a mini.

Glad you don't have to rebuild anything.

[smalltowncowboy]

Alright, I talked to my UNCLE again and he said after 3-4 miles, OD works fine. So we don't have a problem and he can continue driving the toyo. He will sleep better now. He also told me that his wife's Corolla was starting (?) to do the same thing. I told him not to worry, it's just the Japanese way. Thanks alot. When I grow up I'd like be... something other than a mechanic.

[Phi]

Robinhood is correct. Your Uncle's truck is fine