Automatic Transmission shifting problems

[95_Tahoe]

I have a 95 Tahoe and a few months ago it started having problems with shifting after gears in Drive. I was able to pull out a fuze and reset everything. That worked until today, when I put it in drive and pulled out I had no power. It was almost like I was staring out in 4th not first.
I took it to a transmission shop thinking it was time for a rebuild. The diagnostic scan showed my transmission was running perfect. I asked if maybe it was the transmission solenoid's but I was told it wasn't.
Does anyone know what else it could be? All my fluids are fine, no odor or anything.
Please help!

 

[SunlitComet]

does this match your problem?
Transmission goes into gear but feels very sluggish like the brakes are on, but it will roll easily (starts out in 4th gear), you manually shift to 2 to get it moving, once it's moving you put it back in OD and the car shifts 3rd to 4th on its own and locks the converter at the appropriate time.

Shift B solenoid failed. Or a wiring problem from PCM to Transmission.. or PCM.

 

[95_Tahoe]

Sort of. It starts out in fourth I think and never switches gears on its own. I have to manually do it.
I replaced the ignition module and still having the same problem.

 

[SunlitComet]

then that leaves a Vehicle speed sensor, Throttle position sensor or a goofed up pcm.

do you have access to a scanner that can read live data?

 

[95_Tahoe]

How do I check those?
I replaced the ignition switch and learned that the vehicle will run right for a few turn if I disconnect the battery. But then after it sits an I try to sart it again it goes back to having problems.

 

[SunlitComet]

Generic GM Automatic Transmission Codes

Without Onboard Diagnostics (OBD-II)​

Code​

Problem

Code​

Problem

21​

TPS circuit

66​

3-2 Control solenoid circuit fault

22​

TPS out of adjustment

67​

Torque Converter Control (TCC) solenoid circuit

28​

Transmissionmission range pressure switch

69​

Torque Converter Control (TCC) stuck on

31​

park/neutral switch

72​

Speed Sensor (VSS) circuit loss Transmissionmission output signal

36​

Transmissionaxle shift control (3.8L)

73​

Transmission pressure control solenoid

37​

brake switch(4L60-E Transmission)

79​

Transmissionmission fluid temp high

39​

Torque Converter Control (TCC) knock sensor shorted(4.3L)

81​

Transmissionmission 2-3 error

58​

Transmission code-TTS temp high

82​

Transmissionmission 1-2 error

59​

Transmission code-TTS temp low

83​

Torque Converter Control (TCC) solenoid circuit fault

How to get Trouble Codes​

Turn ignition switch to OFF position
Locate Data Link Connector (DLC), see image below.
Jumper the A&B terminals(a paper clip or a jumper wire work ok)
Turn Ignition switch to ON position.
Count the flashes on the "CHECK ENGINE" or "SERVICE ENGINE" light.
FLASH, pause, FLASH, FLASH = code 12
NOTE: Some 94 & 95 models do not have the B terminal. In which case a scanner is required.
NOTE: Some 94 & 95 models that DO have the A & B terminals still require a scanner.
All vehicles after 96 are OBDII,and require a scanner to access them.​

12 Pin Data Link Cconnector (under dash)​

A - Ground F - Torque Converter Control (TCC) B - Test Terminal G - Fuel Pump C - Air Injection H - Brake Sense Speed Input E - Serial Data M - Serial Data

---------- Post added at 06:36 PM ---------- Previous post was at 06:35 PM ----------

the connector should be under the dash near the steering wheel.

 

[95_Tahoe]

Thank you for all your help. It is greatly appreciated.
But the scanners can't read any of the codes, and I replaced the EPC, filter and changed the fluid and it still won't run right.
The Tahoe is now stuck in Limp mode now matter what I do. Disconnecting the battery doesn't fix anything now.

 

[SunlitComet]

limp mode is a tranny with out power. does the tranny gear selection indicator light up one notch forward of the lock position of ignition switch?

 

[95_Tahoe]

Yes it does.

 

[SunlitComet]

then withe key in same position look for system power on the pink wire cavity on tranny plug cavity "E".

Inline Harness Connector C122 Engine Side

this is from a 1999 tranny but wire location should be the same although plug shape might vary a bit.


A/T Inline Harness Connector End Views