an acquaintance of mine has a '99 blazer with the 4l60e that is having problems shifting. it was described to me as delayed upshifting, sometimes not shifting into 3rd or OD. he changed the fluid and filter before i got a chance to hook up my OBDII scanner and said the fluid was brownish. here are the codes:

P0101
P0147
P0452
P0453
P0740
P0785
P1860
P1810

i know from experience that a dirty MAF sensor can cause problems similar to the ones he's having, but the last few codes lead me to believe that the transmission is failing. any thoughts?

 

P0101 - Mass Air Flow System Performance
P0147 - HO2S Heater Circuit Bank 1 Sensor 3
P0452 - Evaporative Emission Control System Pressure Sensor Low Input
P0453 - Evaporative Emission Control System Pressure Sensor High Input
P0740 - Torque Converter Clutch Circuit
P0785 - Shift Timing Solenoid
P1860 - Torque Converter Clutch PWM Solenoid Circuit
P1810 - TFP Valve Position SW. Circuit Malfunction

Now, seeing all of that, I would clean the MAF sensor as well as clean and inspect all grounds under hood. Then clear the codes and drive it for a bit.

 

i cleaned the MAF sensor and connector and cleared the codes. the "shift/timing solenoid" code returns within about a minute of the engine idling in park. we took it for a 4 or 5 mile drive and a "manufacturer controlled transmission" code returned. i didn't catch which code it was, but i'm going to guess it's for the TPF valve because i seem to remember the scanner naming the TCC codes. those were the only two codes that returned, but i didn't get to drive it much.

unfortunately cleaning the MAF sensor didn't fix the problem. the engine seems to run fine, but the truck is very slow to accelerate (kind of feels like the transmission is slipping), it never shifted into OD while i was driving at 50-60mph, and it wouldn't kick down when it was supposed to. the upshifting is not harsh.

the truck does have some electrical issues. they told me that the brake and reverse lights don't work right, the hazard relay always clicks (might be the switch), and the digital gear indicator doesn't show which gear the transmission is in. we didn't check the grounds because it's too damn cold.

 

I would pull the electrical connector on the transmission. Not having a the gear indicator working leads me to believe that this may be caused by corroded or otherwise compromised connections at the transmission.