2003 ranger trans shift trouble

[Engineer78]

I have read everything here on transmission shifting problems and still haven't found the answer to my mine. So here it is:

2003 Ranger with electronic controlled transmission.

Symptoms: works/shifts fine when first started and for the first 3-4 stops. After that, it does not want to down shift when I stop or it shifts hard and FAST to third and overdrive. The overdrive light starts flashing.

If I turn off and restart the engine, the problem clears for the first 3-4 stops and returns.

Shifting the transmission manually, it works fine. I changed the transmission filter and fluid. Adjusted all linkages according to the manual and checked for defective wiring.

I have concluded the problem is somewhere on the "Control" side. The transmission is controlled by the Transmission Control Module (TCM). Does anyone know what "inputs" the TCM uses to make shifting choices? I would think Throttle Positioning Sensor (TPS) would be one, does anyone know of any others?

[Engineer78]

After having 3 different shops tell me I need another transmission, I finally found the problem. It had ALMOST nothing to do with the transmission. In my model of Ranger with an electronic transmission, there is a large junction plug under the driver's seat that passes through the floor board. All transmission control wiring, speed sensor wiring, and ABS rear brakes pass through this large plug. The plug is water tight from the bottom (outside), but NOT from the inside!!! If any moisture gets into the plug, you get all sorts of problems. At one point I had my brakes pulsing when I stopped, ABS light comes on, Seat belt silenoid chattering, Trans Over-drive light flashing codes, and the transmission shifting like crazy. Then I found a service bulletin online about the problem. You have open the plug clean all moisture and corrosion out, then re-assemble. The service bulletin actually says to replace the Male, female, and all the wire pins that make up the juction plug. Instead, I cleaned both halves of the plug with NAPA spay on battery post cleaner, it eats corrosion. Then I sprayed the plugs with electric contact cleaner and quickly used air to blow it dry. Then I sprayed a coating of silicone lube into the plug and re-assembled it. Transmission works great and no more problems.

Just think, if I had my transmission rebuilt, I would still have had the problem, what would they have blamed the problem on? Good luck.