Greetings. long time lurker, first time poster.

There seems to be some confusion on the web with regards to whether or not the PCM is protected by the IOD fuse and I'm hoping someone here at DF might have a definitive answer.

The reason I inquire is that I have an approx. 350 mA parasitic drain on that fuse in my '99 Dodge Ram 1500 5.9.

Until my work schedule allows me time to investigate further I'll just keep pulling the fuse upon parking. However, the truck now requires an inspection renewal and I'm trying to figure out if pulling it is resetting the drive cycle in the pcm.


Thanks

 

What year is your truck?

Best I can tell...... PCM gets it's back up power thru the PDC. Not the junction block. (fuse block in the dash.)

 

Thanks for the response H Y.

It's a 99. What you're saying makes a lot of sense, I was wondering myself why they would run such an important circuit from what is effectively an auxilary panal.

Most of the info I found on this was related to some sort of solution(or possibly urban legend) to fuel/timing issues. Supposedly if you reset the pcm and it has to "relearn" your driving pattern it will fix some of these issues. It was also suggested this be done after spark plugs are changed.

Regardless as to whether this is true or not, most were saying that pulling this fuse would accomplish this

 

Disconnecting the battery will reset the computer..... That's about the only way I know that works for sure. Probably a labeled fuse or two in the PDC that would do it as well.

And yes, the computer DOES learn your driving style..... When I worked in a dealership, and folks came in complaining their car was "gutless", if we didn't find anything else wrong with it, we would reset the ecm, then take it out and wail the tar out of it. Customer was always happy with the new found "power"......

You should reset the PCM after changing any of the sensors it pays attention to. Let it learn the new sensor, and in some cases, it needs to figger out the 'zero' values of the new ones. (TPS, IAC) For plugs, yeah, maybe. Not required, but I bet it sure wouldn't hurt.

 

Just wanted to follow up on this issue(kills me the way so many thread starters don't bring helpful closure to a topic once they've solved it).

First of all, a thousand THANKS to HeyYou for the kind help. The information was 100% correct. The pcm does not go across the IOD fuse; I was able to register a drive cycle in the memory and pass the inspection.

Second, I would like to pass along a critical piece of info to anyone else that might have this problem.

If you choose to disable this fuse until you find the problem, you will need to enable it for the inspection. The 14th pin on the OBD socket is powered by the circuit and if unavailable it will cause a "CANNOT COMMUNICATE" message to appear on the scanner and you will fail. (found that out the hard way).

 

Are we having fun yet?

At least you passed inspection.

 

disconnect any audio equipment, security system, remote start. see if the problem disappears.