These cars will usually throw a p0700 along with a P07XX,
but it does not make sense that there are no basic codes, so a full-fledged scanner indeed needs to access the TCM.

 

This is exactly what my 1999 sw2 just started doing. Did you figure yours out?

 

They never came back.

Sigh

Do you have any service engine soon codes? You can get them read at AutoZone or similar for free if they are basic codes but you will probably need a full-fledged scanner to access the transmission codes.

 

I have not but I have learned a bit more. When I have the issue I now pull over and turn the car off and on several times. The problem always goes away and the car drives fine. For some reason, since I’ve started doing this the transmission issue is occurring MUCH less frequently. I do still need to get it diagnosed at a shop…

 

For the sake of information, the L Series cars with four cylinder engines have a PCM (Powertrain Control Module) which monitor both engine and transmission. The L Series cars with V6 engines have an ECM and a TCM. The transmissions in the L Series cars are the 4T40E for the four cylinder models (LS, LS1, L 100, L 200, LW 200, and L300.1) and 4T45E for the V6 models (LS2, L300, LW300, L300.2, and L300.3). These transmissions were corporate GM products unlike the S Series transmission, TAAT, which was specific only to those cars with the 1.9L engine.No other vehicle within GM used the TAAT transmission.

 

Pierrot, there you are! How have you been? My LW300 has been great, the L200/5 has been parked collecting dust.
Please continue here, you have been missed.
Andy

 

Thanks for the info! I appreciate it.