1994 cutlass 3100 stuck in 3rd gear.

[94 cloisonne convertible]

I have a 94 cutlass convertible and its stuck in 3rd gear. 

    I have power going to one of the prongs on the plug into transmission.   Are any of the other one suppose to have power ?

   I bought the car this way so, i dont have alot of history as to what was going on before. is it the solenoids on the trans or something else going on?     Thanks for any help..

[55trucker]

The easiest thing to do is to get a scanner on the powertrain to do a KOEO system check, the scanner would run thru the (4T60E) trans commands to test all sensors for response.

But...if the vehicle speed sensor fails the PCM no longer knows what the final drive assembly is doing, usually code 24 is set & third gear is forced.

A scanner is not something everyone has, you might save yourself some concern & let a trans shop do the check.

[94 cloisonne convertible]

I borrowed a scan tool it has a code set for the tps ( i just did replace that a day ago because the car does have a high idle usually arounf 1500 rpm.   It didnt change the idle of it.  

   Also a code set for transmission temperature.

  On the scan tool it showed it as a negative 40 Celsius.     Where is the temperature sensor at? Can it be accessed from the pan or is that in the side cover?   Thanks 

Edited June 29, 2020 by 94 cloisonne convertible

[55trucker]

Ok,

 

the plot thickens, the PCM is not receiving the correct signal from the ECT? (engine coolant temp),   a -40 is the default (no signal) display, it could be a wiring harness issue, bad contact at the ECT harness or a failed ECT. Seeing as the ECT signal is out of whack the PCM can't set the correct fuel mixture, won't idle correctly & will not go into closed loop.

 

When you mention a trans temp code is that a code 58 or 59 or 79 or 80?

none of those would display on the check engine light....but would have nothing to do with an incorrect idle situation..

 

see this exploded view of the 4T65 trans, item 391 is the TFT temp sensor.....I'm assuming that it is internal, 224 is the converter harness That is internal

 

 

Edited June 29, 2020 by 55trucker

[94 cloisonne convertible]

The codes are 35 and 59

[55trucker]

Code 35 is an incorrect idle rpm, 59 is the low temp trans fluid.

You mentioned that a tps code was set....21 or 22? I take it that you cleared the code.

when you did the KOEO test the scanner went thru the sensor tests and all the trans solenoids responded as they should?

[94 cloisonne convertible]

A little update i havent been able to dig into it much but i just noticed the transmission temperature is -39 Celsius when key is on and 150 celcius when key is off.

   I own another w body a 95 grand prix and on that one it shows same reading key on or off.

    Another thing to mention when i bought the car the steering column was busted. I did replace the steering column but used my ignition.   I

Any ideas ?    Thanks again

[55trucker]

Interesting..a scanner shouldn't read any info until the ign key is set to run.........what are you using as a scanner?

[94 cloisonne convertible]

A snap on mt2500 scanner.  

[55trucker]

Just to satisfy my curiosity....

disconnect the wiring harness from the trans housing, now do the same scanner check again, when the scanner attempts run thru the solenoids & the temp sensor the display should be *no information*  or blank

[94 cloisonne convertible]

So the temp sensor stays at  negative 39 celcius key on or off when its unplugged 

[55trucker]

The temp sensor isn't staying at anything for the moment, you've taken the sensor *out of the equation*. What you're reading on the scan tool display is what the PCM is seeing.

Now what you need to do is some diagnostic detective work, you'll need a DVM (digital volt meter) & a jumper lead.

The TFT is nothing more than a thermistor, it varies it's internal resistance as the temp of the fluid changes. The supplied reference voltage from the PCM should be 5v, when the trans fluid temp is low the resistance is high, as the temp rises the resistance goes down. In other words the voltage signal back to the PCM when cold should be lower than what is sent when the trans is hot.

You'll need to test the resistance of the thermistor (both cold & warm), you'll need to check the circuit to & from the PCM for errors.

The wires in the trans harness to & from the PCM should be yellow on the reference side & black (ground) back to the PCM. The pin # at the PCM should be C14 (yellow conductor). The internal grounds should be terminals B1 & D10 (blk/wht).

With your scan tool connected & ign on, harness at the trans disconnected, jumper the yellow to the blk,  read the  display, it should be near maxed out. Now remove the jumper, the reading should drop to near minimum. If those readings are correct then the circuit can be assumed to be good. If not then you need to go deeper into the circuit or test the PCM itself.

Next test the sensor, set the meter to ohms, connect the leads to the sensor pins, read the meter display cold, start the engine & let the powertrain warm up. Watch the meter display, the reading should change as the trans temp goes up.

Generally most TFT's are what is known as *negative* coefficient, If the sensor readings you get are reversed to what I've described then the sensor is *positive* coefficient.

 

[kzwslf]

Sorry for joining this post late.  I see two different problems that may or may not have the same cause.

The stuck in third gear and the code 59.

The ECM should ground both solenoids A and B for first gear.  When both solenoids are OFF you get third gear.

I don't think the code defaults the trans to third gear.

Attached is the diagnostic page for code 59.  All you really need it a meter and the wiring diagram. The code 35 can be caused by disconnecting the battery when the Idle Air Control has carbon built up on it.  Cleaning the IAC and disconnecting the battery may correct the idle.

Circuit 1227 Yel/Blk should be 5V with the key on engine off (KOEO) No voltage here will cause the code 59 but not the third gear. An open circuit in the TFT sensor with cause it to read -40 (or -39) degrees. Grounding circuit 1227 will read something around 300 degrees.

Circuit 808 should be 0 volts and should have low resistance (less than 2 ohms) to a good engine ground.

Circuit 441 should be 12 volts.

Since all these circuits depend on a ground through the ECM to work I also wound check the ECM grounds.

ECM grounds are terminals B16 C17 C1 and B32.

 

Phil