95 T4R auto trans/ECU/ECM diagnostics

[NC_Jones]

My "New" 95 recently stopped upshifting into OD. I have downloaded a Toyota shop manual for this vehicle and have begun following the flow charts and trouble-shooting guides in trying to diagnose this issue.

She passed the road test and was able to upshift into OD with the solenoid wire disconnected. The second road test left me a little confused. In testing the voltage at Terminal TT at DLC1, the question is asked, "Does the voltage rise from 0V to 7V in sequence?" I am not sure what they mean by "in sequence" exactly but the meter did jump from 1.x to 2.x and then stayed at 4.12 volts until I used the brake pedal. In the flow chart they offer a 0 to 5 volt solution path, a 0 volt path, a 0 to 3 volt path and a 0 to 7 volt path. The confusing part is that they use arrows rather than the word "to" as in 0 (arrow) 5 V. For now I have assumed that my 4.12V reading falls into the 0 to 5 volt range, as if they meant the arrow to express a range from 0 to 5 volts. Is this assumption correct?

I followed the flow chart using this assumption and did the next test. The truck passed the voltage test for the OD2 and e1 terminals, 12 volts with the O/D main switch on, no voltage when switched off... groovy. Then to the next item, "Is the voltage between ECM terminals OD1 and E1 as follows? Approx. 5 V" Well, it read 12 volts. So I guess the answer is no and moved to the next question, "Is voltage between ECM terminals OD1 and E1 normal with the cruise control ECU connector pulled out?" Again I got a 12 volt reading. Is this "normal"?

If this is normal then I am directed to replace the cruise control ECU. If this is abby normal then it suggests to replace the ECM or possibly faulty wiring with the cruise control harness.

I ran the throttle position sensor test and passed that test as well.

I am just looking for a little clarification on this tech manual. I'd hate to spend any money needlessly since I haven't worked in a while. Every nickle counts when you live within your means.

Thanks...

 

[fourwd1]

For now I have assumed that my 4.12V reading falls into the 0 to 5 volt range, as if they meant the arrow to express a range from 0 to 5 volts. Is this assumption correct?

No, I don't think it is a correct assumption. They are looking for a signal to change from one value to the other, not any value in that range. If you look at other parts of the flow chart they do specify an acceptable range, and the values are separated by a dash -

More proof is because of just what you stated here

In the flow chart they offer a 0 to 5 volt solution path, a 0 volt path, a 0 to 3 volt path and a 0 to 7 volt path.

If it could be anywhere between 0 and 7 volts, there would be just one path.
The 4 possible outcomes all point to something different being bad.

BTW, I'm lookimg at an FSM, not just going by your post.

the next question, "Is voltage between ECM terminals OD1 and E1 normal with the cruise control ECU connector pulled out?" Again I got a 12 volt reading. Is this "normal"?

There is a chart which shows the "normal" values between different terminals on the ECU.

Hope this helps.

 

[NC_Jones]

Thanks, your input is most helpful. Just goes to show ya what they say about assuming things...

The more that I delve into this vehicle, the more unease I have about driving it very far from the house. Despite having no O/D, it seems to run fine BUT it may be on the verge of a head gasket blow out on top of all else.

I was not very smart when I bought this car. My faith in Toyota's has been high up till now. Still, this is a 16 year old car and I trust my shadetree skills to fix most problems.

What I discovered yesterday makes me want to keep close to home when driving this beast. When I bought it, there was what appeared to be white paint in the front drivers side wheel well. The seller stated that he ran through some fresh paint on the highway. Well, the trail of "fresh paint" appears to have originated in the overflow tube on the cooling system overflow bottle. Ugh. The water temp gauge acts like there is no thermostate present. It takes a long time to come up to temp, cools back down and fluctuates while driving, heats up while sitting. I suspect that this thing was overheating, maybe the begining signs of a head gasket issue and someone added an after market gasket repair sealant to the cooling system. Just a half educated guess.

Despite the lack of O/D and the temp gauge fluctuations, this thing runs and drives smoothly. I ran it for 90 miles on Monday, half of which was on the highway at 65 mph and got 16 mpg. I am going to run a fine tooth comb over this thing and probably do a pre-emptive head gasket repair after I fix the computer issue.

Thanks