help! TCC error (code 38)

[94FSblazer]

Vehicle: 1994 Chevy Blazer, 350 tbi, 151,*** miles, OBDI, original tranny

-Hey guys,
I have a code 38 (Brake position switch error) coming up when retrieving my codes.
I have had constant stuttering/shudder while accelerating as well as at constant speed. I would feel a slight jerk/hiccup and the RPMs would jump/drop up and down for a brief second (maybe 100ish RPMs each time). This keeps happening unless I let off the acceleration.
I was not getting a code at first. I now have a code 38 (Brake pedal position (BPP) switch/ torque converter clutch (TCC) error)

I am having a hard time finding information about diagnosing this and solving the issue. What are the steps that I need to do to test this? I am guessing this is one of the switches under my dash at the brake pedal lever? Hoping that I do not need to drop the pan and replace a solenoid. I have tried depressing the brake pedal without engaging brakes while cruising, but I see no change in RPMs, or the symptoms getting better. This happens in Drive or Overdrive.

Any help is appreciated!!!!! This is my DD, so i have been still driving it (very carefully), but I am afraid I am about to chew up my TC if I do not solve this soon!

*Side note* - about 7 weeks ago, I was making a trip from Detroit to Chicago, and when I got on the highway, I had a hard time getting up to speed (wouldn't downshift like usual). There was a slight hesitation, then suddenly, what I thought was a backfire happened. I pulled off and pulled out my handy paperclip to check the codes. I believe the code that came up was code 83 (Torque converter clutch (TCC) solenoid, pulse width modulated – circuit malfunction). I am not 100% sure if I'm remembering that right tho. I checked my engine and reset the computer. This did not happen again unless I was cruising around 2500 (75mph) and it would pop, or backfire. I would slow down then just ease back into my acceleration and it wouldn't happen. Seems like I am not able to shift into overdrive from 3rd. Maybe this is related to my code 38? That code is no longer stored in the system, and I have not been over 50mph since then (I do 99% city driving).

THANKS FOR ANY HELP!!

 

[94FSblazer]

Seems to be the worst right before the shift and right after. Really bad today. Probably going to stop driving it if I can until I can figure this out. Really don't want to take it to the shop, but may have to if i cant figure this out soon.

 

[Big D]

this is all I could find bud, how to test the switches

https://www.gmforum.com/electrical-133/tcc-solenoid-switch-284972/

My truck was going in and out of lockup at freeway speeds and hard shifting and late shifting, but I had a TPS sensor code, it took 2 TPS sensors to fix it, Make sure if you buy new sensors to test them before installing.

 

[94FSblazer]

this is all I could find bud, how to test the switches

https://www.gmforum.com/electrical-133/tcc-solenoid-switch-284972/

My truck was going in and out of lockup at freeway speeds and hard shifting and late shifting, but I had a TPS sensor code, it took 2 TPS sensors to fix it, Make sure if you buy new sensors to test them before installing.

Thanks for the reply Big D! That article will help. I'm going to try to test my solenoids this weekend.
I did replace the TPS about 2 months ago along with my IAC about 6 months ago. Both ACDelco products. I'm going to hook up my OBDI data log device and see what my tps is reading while Im on a drive. I think after that I'll take it out and test as well.

Hopefully one of these tests will show what my issue is! It's driving me insane! And I've been so damn busy lately that I havent been able to take the time to really check it out or do tests .
Thanks again for the reply !

 

[94FSblazer]

Well damn....still no fix.

On Monday I decided to take a look at my brake switch under my dash. Unplugged the connector, pried off the retainer clip (pain in the ass!) and slipped it off. Pretty gunked up as well as a black contact point, so i decided to change it. Brand new one in, and no fix to my problem.
So I tested my TPS sensor next. With ignition turned to on, I was reading 0.655v with the throttle closed, and 4.51v with throttle wide open. Slowly turning throttle open and closed, I did not see any dead spots. Also, the connector was getting 5v power. So rule out TPS sensor as my problem?
Going to look into properly adjusting the brake switch to see if this new one isn't quite right.

Any other suggestions for where to look?. Maybe shift solenoids in pan?
Unfortunately, Im going to be extremely busy over the next few days, so I do not think I will be able to really work on it much. Looks like Ill be hitching a ride with Joe Metro for now until I figure this out.
Might bring it to a shop next week if I can't figure anything out.

Thanks again for any help! Driving me crazy!