Receipts from the dealer from the first time, a year ago, the O/D light flashing occured state that the main electronic transmission cover was accessed and the solenoid valve body ($83 for the part) was replaced. Then the dealer handed it back to me without the O/D light flashing. The car is now out of warranty but only has 30,000 miles on it.
The difficulty I have is that I live in Ohio which is very flat and the only place around that I can get it to flash is about 35 miles away. When I drive it to New York to visit my son is when the O/D light flashes quite easily. Therefore, here, even if the dealer/tranny repair shop thinks it has it fixed, they probably won't drive 35 miles away to test it. They take it for a local drive, just hand it back to me and say it is OK.
Hopefully, the above covered the solenoid assembly, leaving only the valve body as a possible problem.
Could it not be the computer program that is a problem since this O/D light flashing is such a common problem with Contours/Probes/Mazda 626's, all with the CD4E ATX? That is why I was asking about the chip addition.
