odb1 high stall problem

i was reading the pdf for the latest version of the $ee def file on the tundercar site and saw one that one of the switches was called "vehicle speed diag", which was dtc 24. that got me to thinking.

from the 94 camaro gm service manual:

"dtc 24 will set when:
(automatic transmission) - transmission output speed is less than 250 rpm when the engine speed is greater than 3000 rpm, not in park or neutral, adn dtcs 21, 22, 28, 33 and 34 not set and map greater than 20 kpa, but less than 99 kpa. all conditions met for 3 seconds.

action taken:
the mil will illuminate, transmission will default to third gear, high transmission pressure."

does this sound familiar to anyone? i can't say 100%, but i disabled dtc 24 on the switch table, and have yet to run into the same issue. however, i only tried this tonight. only time will tell. but after adjusting my shift tables ( i lowered the first gear shift to 36 mph) i have gotten several full throttle second gear shifts, breaking the tires loose.

can someone else please try this out, and see if it will work for anyone besides me. the desciption of the code and the symptoms match too closely. it would be nice if a fix was as simple as turning off a diag code.

good luck!!

I would talk to Madwolf or Doom Master about this..Both of them can fix the problem.

I've finally managed to fix the problem on flyinZ's car, thanks to some help from Madwolf and Dan K (we all contributed to fixing it on his car). It mostly has to do with the shift points and the torque converter's lock/unlock points. The problem we had on flyinZ's car was that while on street tires he never had a problem, his slicks are slightly larger than his street tires, which changed the shift points slightly. Because of this, he would bounce off his rev limiter due to the change. When he was getting the SES light, it was because his TCC points were not correct for his stall. I'm not sure if the diag 24 code would work, but it might if it prevents any reading of the diagnostics from the trans to the PCM, therefore stopping the torque converter from locking/unlocking improperly. However, you might still bounce off the rev limit and not shift properly.

if you read my post closely, you would see that i even pointed out that i had to change the shift points. my guess is that the computer shifts based on driveshaft rpm (or mph), and with the higher stall, it lowers the driveshaft rpm as related to the engine rpm. that is, 6k rpm with a stock stall is 45 mph, but with a 3k stall, it is about 35 (with my 3.55 rear and and 245/45-16 tires).

so, i feel, both are important. shift points must be lowered, for proper shifting thru all gears (i had noticed that i would hit the rev limiter in third gear). but i think that disabling code 24 would help in the situation that you are at the starting line (or stoplight), and really hitting the stall. i think that would clearly set code 24, at least as explained in the service manual.

cliff notes:

shift points must be adjusted, on like 8 different tables. also, code 24 must be disabled to allow a high stall power brake. both must be done.

i had done a lot of searches on this issue, and no one ever mentioned code 24 before. this might be clue to those for whom the previous software fix did not work. if you have adjusted your shift tables, and you still have an issue where it will go straight from 1st to 3rd, try this.

Originally posted by conquest lt1
can someone else please try this out, and see if it will work for anyone besides me. the desciption of the code and the symptoms match too closely. it would be nice if a fix was as simple as turning off a diag code.

That does sound fairly similiar. We need some test victims for this and see if it does anything on anyones car. :)

Originally posted by conquest lt1
if you read my post closely, you would see that i even pointed out that i had to change the shift points. my guess is that the computer shifts based on driveshaft rpm (or mph), and with the higher stall, it lowers the driveshaft rpm as related to the engine rpm. that is, 6k rpm with a stock stall is 45 mph, but with a 3k stall, it is about 35 (with my 3.55 rear and and 245/45-16 tires).

so, i feel, both are important. shift points must be lowered, for proper shifting thru all gears (i had noticed that i would hit the rev limiter in third gear). but i think that disabling code 24 would help in the situation that you are at the starting line (or stoplight), and really hitting the stall. i think that would clearly set code 24, at least as explained in the service manual.

cliff notes:

shift points must be adjusted, on like 8 different tables. also, code 24 must be disabled to allow a high stall power brake. both must be done.

i had done a lot of searches on this issue, and no one ever mentioned code 24 before. this might be clue to those for whom the previous software fix did not work. if you have adjusted your shift tables, and you still have an issue where it will go straight from 1st to 3rd, try this.

I read your post closely. If you read mine, you don't see anywhere in there that I say your idea is incorrect or won't work. It's worth trying, the question is whether or not it will still bounce off the rev limiter. It might also allow an OBD1 car to brake stall more effectively as well. We'll have to try it and see.