Hey everyone. Fiance just got a 99 Durango 4x4, 360 V8 that will not go into overdrive, so of course it runs at 3000 at around 65 mph and sucks gas. I just repaired the famous intake pan gasket leak, and it runs a lot better now. Also has a IAC valve system problem(Code 505) and its in the wiring or PCM. It also has the wonderful no bus thing going on. Shuts off and when I wiggle the connector closest to the firewall on the PCM it is fine. I know I will need a new one sooner or later.
When I redid the intake, I put in a fail safe 180 degree thremostat since I know these have cooling problems. Works great, no where near overheating but lower temps than normal obviously. From reading a 2002 FSM it states that the overdrive and TCC wont function until engine temps are warmed up. Whats the minimum temp for it to start working? I dont think it was working before I repaired the intake, gas mileage sucked then to. I didnt drive it on the highway until after I repaired it.
There are no codes I can get with a cheap code scanner, but Im assuming you cant get trans codes with those and need a DRB?
When i push the OD switch on the shifter the light comes on in the dash, so I think the switch is ok. Other than no OD the trans works great and smooth. Hopeing its not a PCM problem, too expensive to fix that. Is there a way I can bypass the PCM controls with a manual switch temporarily? Turn it on and off as needed? Whats the voltage needed to operate it? Dont want to burn it up with full 12 volts since some sensors and stuff only use 5 volts or whatever. Thanks.

 

Hopefully you will fare better than i did with this same issue... i battled it for a year and a half. tried everything that the manuals said and never really found the problem. About a month ago i suddenly lost reverse... and just the other night i lost the rest of the gears... i am currently in the process of getting a new (used) trans to swap into it.

You might want to download the 1998 FSM from the DIY section as that will have information closer to your truck than the 2002 one. here is a chart with some things you can try....

 

One other thing i thought of and forgot to mention... in my journey to find the problem, there is a spring in the valve body that i was told that the OEM one is common to snap and cause no OD.. mine was snapped in half when i looked at it and i replaced it with a thicker one made by sonnex..

 

Yeah, I saw that post while searching the forum. I tried putting cardboard in front of part of the radiator but still doesnt do anything with the temp up where its supposed to be with the stock thermostat, or even warmer. Funny thing is now the rpms are now lower than before, like 2600 at 65 mph, strange. Rpms dont go back up when i turn the OD button off though, its like its stuck on now, lol. At least I ruled out the temp being the problem. Going to check fuses, next easiest and free check. The rest seem to require the DRB.