Concentrate on that solenoid first

Question:

I have a garaged 1998 Dodge Dakota 1⁄2-ton pickup with 4-wheel drive, a 3.9liter V-6, and an automatic transmission. The vehicle has 51,000 miles and it has an electrical problem I cannot solve. When it’s rainy or excessively damp outside my check engine light will come on and I am told it registers trouble code 37, which indicates that the solenoid inside of the transmission should be checked. Upon initial onset of the light the truck starts out in 2nd gear. After three or four stops and starts the transmission will shift properly, but the light still stays on until conditions become dryer and then the light eventually goes out. I have tried cleaning all of the wire connections going to the transmission and all grounds I could locate. I have pulled and reinserted the power control modules to see if any invisible corrosion might rub off the contacts but none on these actions have helped. The dealer wants $400-plus to rework the transmission and they don’t seem concerned that the problem only happens in damp weather. Are there any other actions I can take or are there other things to look for?

Answer:

The fact that the trouble code is set only in damp weather would seem to point to a poor electrical connection. Trouble code 37 indicates a malfunction with the torque converter solenoid and the actual function of the solenoid itself would not be affected by damp weather, if for no other reason than the solenoid is inside the transmission where it’s fairly well isolated from dampness in the air.

I’d double-check all wire harness connections again. Get a shop manual with wiring diagrams if you don’t already have one and use that to make sure you check all connections related to the transmission, not just those you can immediately see when you crawl under the truck. Clean any corrosion or dirt you find and coat connections with dielectric grease, an insulating material made by Permatex, CRC, and several other reputable manufacturers. Dielectric grease goes a long way in protecting electrical junctions from the impact of moisture.

You mention that the dealer wants $400 to rework the transmission but what makes you or them think the transmission needs to be reworked? The diagnostic trouble code your truck records indicates a problem with the torque converter solenoid, not a problem with the entire transmission.

Consult your shop manual to confirm, but I believe that for your year truck the solenoid is mounted at the bottom of the transmission, just above the transmission’s oil pan. Before paying someone to rework the transmission I’d remove the pan and have a look at the solenoid to see if anything is obviously amiss with it. Before taking the transmission out and apart I’d replace the solenoid with a new one even if there is nothing visually wrong with it.