Our '94 Dakota 3.9L won't idle. New IAC didn't help any. Intermittently the truck would refuse to shift into overdrive but most of the time it works okay.

If I disconnect the battery cable the reconnect it, it will idle fine for a long time. But the next morning (ie when my daughter tries to go to work) again, no idle.

The only code that's set is 53. Before I drop $200 on a computer, is there anything else to look at?

 

I'm assuming you already replaced the IAC, which even new out the box lots of them are bad. If you still have the receipt take it back get a new one.

When you reset the battery does the code come back up. Are you positive you read the codes correctly?
53* Internal PCM failure
https://dodgeforum.com/forum/1st-gen...-96-codes.html

 

Yes I replaced the IAC, even though it appears both the old and new are working. I can see the thing moving back and forth.

After disconnecting the battery the code is gone. The truck starts, runs and idles properly even after it's warm. I can restart it without much trouble. But after it's cooled off again (like the next morning), no more idle and I get a code 53 again. I'm positive I'm reading codes correctly, I've done it many times trying to fix this and the results are consistent.

 

Then I hate to say it but you may need a new pcm.

 

You were right. I got a used PCM off ebay and that solved the idle problem.