I have codes P0700 and P0780 on my 2000 LX 4 cyl AT that has 200k miles on it with its original transmission. Three times in the last two months the transmission is sluggish and the D4 light blinks. It's usually been sitting in very cold weather for a while when it decides to do this. After driving it for a while the problem goes away. ATF still red, no burnt smell, and fluid level ok. The 780 code points to three possible solenoids being the issue, then internal problems if it's not one of them.
Using the test procedure for the solenoids I found on Scribd http://www.scribd.com/doc/19721454/Test
here's what I found.
The torque converter clutch solenoid appears to be ok. It was well within the Ohm range, the screens were pristine, and the solenoids clicked when electric was applied.
The clutch pressure control solenoids visually looked ok and seemed to respond appropriately when I applied the eletrric to them but the resistance was 15 and 14 Ohms respectively for the A and B valves. This is a significant variance from the 3 to 10 listed in the test procedure.
Now for my question. Is it possible the extra resistance is causing my issues? Perhaps with the very cold weather the added resistance is just enough to cause this intermittent problem. I'm hoping this is the case as it's $50 for the new solenoids versus thousands for a tranny.