Tranny not shifting into OD HELP!

[dkanderson]

I have a 96 chevy k1500 and it seems like the trannys not shifting into OD and its not locking up, My temp gauge inside the truck is not working and ive heard that may have somthing to do with it but im not sure.

also where is the sensor for the temp gauge. The tranny is shifting fine in all other gears no slipping.....

 

[ak diesel driver]

The temp sensor the ecm sees is the one in the coolant crossover. You need to be at 160+ for torque convertor to lock. Sounds to me like either a sensor problem or the engine isn't getting warm enough usually a tstat problem

 

[JiFaire]

Good call, AK.

dk, you can check your CTS with an ohmmeter and a thermometer ... the values are listed in the technical library.

 

[bk95td]

The 4l80e has a transmission temp sensor built in it. It can be read with a scan tool. I don't think the ecm controls OD and lock-up enable from temp input.

 

[THEFERMANATOR]

The 4l80e has a transmission temp sensor built in it. It can be read with a scan tool. I don't think the ecm controls OD and lock-up enable from temp input.

The PCM controls lock-up and OD via limiting tables that use TPS, engine temp, AND trans temp. The PCM will not allow 4th gear if the engine is cold as it does this to help warm the engine up, and lock-up will not occur when the engine is cold to prevent overloading a cold engine or if the trans is cold to prevent pressure spikes from cold thick tranny fluid.

 

[bk95td]

92-93 positively doesn't use engine temp because there is no input to the pcm for engine temp. My 95 locks up and goes to OD about the same distance from home as the 92 and 93 does.:???:

 

[Jess_sr]

My 93 and the kids 95 only have a LU delay for temp.
Then again with the prom being replaced on the 95 who knows what was writen into the program.

 

[THEFERMANATOR]

92-93 positively doesn't use engine temp because there is no input to the pcm for engine temp. My 95 locks up and goes to OD about the same distance from home as the 92 and 93 does.:???:

91-93 has a temp input to the PCM for the glow plugs and auto trans as this is a fairly common complaint with them when the CTS goes bad.

 

[dkanderson]

I got a buddy that owns a tranny shop and im going to take it to him as soon as he gets well, He hurt his back about a month ago and his been outta work the whole time so ill wait and have him put his scanner on it hopfully that will tell me somthing

 

[great white]

OBDII uses internal trans temp to determine lock up IIRC.

 

[great white]

Oopps, may have spoken too soon. A quick look in my 98's stock cal reveals that OBDII (at least my 98) may use both trans and ECT when determining converter lockup:

 

[bk95td]

91-93 has a temp input to the PCM for the glow plugs and auto trans as this is a fairly common complaint with them when the CTS goes bad.

My 92 and both 93s don't have a coolant temperature Sensor. There is a coolant temperature Switch[on the coolant crossover] that turns the fast idle and cold advance on. Glow plug control comes from the glow plug controller. 92-93 uses a different glow control from 94+.