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94 LeSabre Custom Trans has issues


DaddyMac68
02-15-2005, 10:02 PM
I have a 1994 LeSabre, 200K+miles with some transmission issues. The SES light recently came on intermittently and now stays on. About the same time, I noticed the transmission shifting early at slower speeds (in OD or D) while accellerating and when on the interstate at cruising speed - 60 to 75mph - it UPSHIFTS under load. Yes, I said upshifts - as is from 3rd to 4th. Additionally, while the SES light is on, a rapid release of the gas pedal while accellerating causes the enging to die. I've seen postings about some valve in the tranny going bad and some about the TPS failing so there's probably no textbook solution. Also took it to my local Auto Zone to get the codes pulled but it is a victim of the ODB-I to II transition - 16 pin connector but not ODB-II compatable so whoever has the pin-out for the transitional configuration, please reply. I can pull the codes myself and go from there...HELP!

avatar307
02-16-2005, 10:13 AM
If it has the 16-pin OBD-II connector, but lacks pin 2, then it is not OBD-II. (Noted simply to clarify what you are saying.)

Since it is a 1994, it's likely you still have the "error codes by flashing SES" function available. Short pin 4/5 (ground) to pin 6, if it available.

If not, then you must read the codes via traditional ALDL serial. You'll either need a special cable and software on a laptop, a GM Tech 1 scan tool, or one of the extremely expensive alternative scan tools that is capable of communicating on GMs old, propriatary ALDL serial. ALDL 8192 baud serial will be located on pin 9.

This information applies only to pre-OBD-II GMs that were equipped with OBD-II connectors. Note that is has taken me 6 months and about 500 printed pages to gather just around double the information listed above.

Apparently, this never became a big enough issue for anyone to document it. ROFL Probably, because the 1994-1995 CH-bodies seem to extremely reselient and are only now, at 150k+, starting to have problems.

Speaking of which, anyone have part of a HydraMatic 4T60, 440-T4, or 4T60-E transmission? Not a whole transmission, I'm too cheap for that. LOL I repaired my air bags computer... and now I have a transmission on my kitchen table. This is officially the FIRST major mechanical failure for my 1995 Buick LeSabre, 171,000 miles.

DaddyMac68
02-16-2005, 12:40 PM
I found your post from a while back with the 2 16 pin configurations and the OBD-II standard config - mine has the 4,5,9,14,& 16 only all the rest are empty so it looks like i'm forced to find the serial cable and computer?

DaddyMac68
02-16-2005, 10:05 PM
I found an auto parts store (O'Reilly) with a code reader in their tool rental program ($200) and it came with a GM specific cable for the 1994-95 model year aldl 16 pin connector - worked great! It ended up being the Throttle Position Sensor (TPS).

Changed it out and SES light is gone and the shifting issue has been resolved, but now the idle surges and seems to be way too low. Is there any other tweaking that might have to be done after changing the TPS?

avatar307
02-21-2005, 03:45 PM
Some people believe that disconnecting your battery overnight will force the engine management computer to lose the custom varibles and reset to defaults. Sometimes this is true, but not always.

Fact is, modern automotive computers learn and adapt to how the engine performs. The computer adapts to read outs from aging sensors as well as factors resulting from an aging engine.

After replacing an old/worn out/broken sensor with a new one, the computer will need to re-adjust it's settings to compensate for the new readings. To maintain reliability, performance, integrity, and emissions the computer will do this in a systematic and slower than expected manner. Sometimes it requires a certain number of driver cycles, other times a certain number of miles, and other times even stranger things.

Everytime you drive the vehicle, try to let the engine maintain full operating temperature for 15 minutes or so. (Full operating temp being when the electric fans start running - not including when the A/c is on.) Many of the sensors on the engine (crankcase, camshaft, oxygen) only give viable readings after the engine reaches a certain temperature. The computer cannot adjust it's settings unless it can monitor the data from all these sensors.

As it is your TPS, it would also be advisable to drive the car at varying speeds, as the computer needs to collect data from the sensors at varying reading from the wheel speed sensor to determine the proper TPS scaling.

As for the 16-pin OBD-1 connector. The do-it-yourself'er needs a computer, serial port, RS232 chip, and 25 resistors, diodes, and other Radio Shack goodies to interface with 8192 baud ALDL. Plus, you need a computer program that will interprete the data. I keep telling myself I'm going to build a cable.... but alas, the transmission is my current concern (I don't really need the cable).

Yes, there are scan tools that will do it without the software. However, those with adapters to compensate for the plug and those that actually do the old GM ALDL are not the consumer end of scan tools. They the GM dealer tool, the GM Tech1 or Tech2, or a $10,000 setup.

Most autoparts stores only carry OBD-II readers. Some carry the old 12-pin ALDL GM code readers, but they don't actually communicate via ALDL. Rather, they are just a simple microchip that triggers the cars "fault codes by pulses" mode, interprets the pulses, and then displays it as numerals.

Good to know that there is a neighborhood store that carries a tool that actually works. I'll keep it in mind if my SES light ever actually turns on. However... from my experience... if they had the tool, they probably couldn't find it.

AutoZone drops the part on the floor and then wants to sell it to me, O'Reillys' sells me parts that go on an engine that was not even available on my model/year/body. When I had to replace the freaking plastic bypass coolant fitting on my intake, I finially just went into the back and found the part myself. (After 10 minutes of them insisting it didn't exist.)

Oh well, alas... compentcey is one of the things you give up in exchange for lower and lower prices. (Damn fools knocked over my coke too.)

ROFL I love'a bitchin'.

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