2000 Dodge Ram 1500 Van Scan Trouble Code P0505

Jul 16, 2008
The Vehicle:
2000 Dodge Ram 1500 Van 5. 2L, 318cid, V8

Scan Code: P0505

Is there a way to check the PCM ?

How do I know if the PCM should be replaced?

What the vehicle does:
The first problem is intermittent.
Sometimes when started it stalls immediately. Occassionally if it doesn't stall right off of the bat then it will stall when the accelerator is let off, such as at a stop sign, etc. It starts fine and when it warms up it drives o. k.

Next came the Check Engine light.

The third problem started as an intermittent backfire when accelerating.
Now it backfires quite often after it warms up for awhile.

The latest problem is that it doesn't idle nice and smooth anymore. I guess it misfires?

Would any or all of these problems be caused by a bad PCM?
What about a bad IAC motor?

Any info. is appreciated.
Nov 14, 2006
First let us know -
vehicle is STOCK, no aftermarket parts ??
THe p0505 is the only code?

Before you throw parts at it....have you worked the problem with IAC?
Inspect TB clean, check for vacuum leaks- there were intake manifold leaking issues -

PS p0505 does NOT say to change the IAC - trouble shoot system.


Nov 24, 2006
kev2 is correct. There are a few possible causes. IAC motor could have failed, but with what you are telling me, it sounds like we have multiple - issues, which leads me to believe the PCM may be the root of the issue. Check the intake for leaks. 318's are notorious for this problem.....wap
Jul 16, 2008
To answer your question about if the vehicleis stock, and no aftermarket parts,
I need to ask you about what do you mean "Stock"?
Like is everything original like it came from the dealer?
I guess I have to answer you with "I don't know for sure, the van is eight years old and we bought it used about a year - year and a half ago. "
It has about 68,000 miles on it.
I know that routine maintenance parts have been purchased at AutoZone and Checker.
If you need to know about any extra add ons, accessories, etc. then no it doesn't have any extras.
It did have one of those yellow lights on the roof. Like what one would see on a utility vehicle. Yellow, spins around, appears to look kinda like it is flashing.
I apologize for not being able to provide you with more info. on this matter.

Yes, P0505 is the only code that the guy who scanned the van revealed.

Now as far as throwing parts at it and the rest of your questions. . . .
I guess I'll have to fill you in a bit more on whats going on.
The van belongs to my boyfriend, he knows a guy through work, figured the guy knows what he's doing because of the guys work history.
Plus, the guy has a scan tool for diagnosing check engine light warnings.
The guy scans the van tells my boyfriend that the IAC Motor needs replaced.
Well, since the problems started out as an intermittent start then die immediately when the accelerator is let up on problem and has now developed the backfire and missing problems, My boyfriend took this guys word and gave him the money to make the repair.
The guy calls the next day and says that he has gone through the wiring and he determined that the PCM is bad and needs replaced.
He said that he didn't install the new IAC Motor because he should replace the PCM first.
He said that he just cleaned up the old IAC Motor and reinstalled it.
By this time what was at first a $100. 00 repair has now become a $320. 00 diagnostic. Plus we now have a brand new IAC Motor sitting in its box on the kitchen table. The van runs worse now than it did before this guy had it.
Yes, the guy has already been paid, plus he says that we still owe him $40. 00 more dollars.
I don't know how he came to the conclusion that that the PCM needs replaced.
My boyfriend asked him what made him change his mind from the IAC to the PCM and he told my boyfriend that he had gone through the wiring and the wiring was fine so that the only thing left was the PCM.
The guy told him that he hooked his meter up to the pins on the PCM first one side than the other. He said he got readings of 4 and/or 6 one way and zeros the other way.
He said he took apart the Throttle Body and cleaned it up and put it back together. As far as if he replaced the gasket/seal on the TB is unknown, He didn't charge for a new one so chances are he didn't replace the seal.
When he put the old IAC back on the van he used the old o-ring instead of a new one.
He said that he put the old IAC back on instead of the new one because he had to order the PCM and that would take a couple of weeks and he didn't want to mix the new IAC with the old PCM in case there is a spike and it ruins the new IAC.
He said the PCM will cost around $450. 00 for the part. And he can get it programmed by the dealer for $40. 00 more dollars. Labor will be additional depending on what he finds after changing the PCM and IAC.
That is why we were wondering if there are steps that should be followed when determining if a PCM is bad or not.
Since it has already cost $300. 00 for the scan/diagnosis only, plus $70. 00 for the new uninstalled IAC Motor that was at first the diagnosis.
Remember, even though the IAC is new and sitting on the kitchen table (the guy had the new IAC when he had the van) the old IAC is still in the van.
The guy did show/tell how to install the new IAC after the PCM is replaced.
That way my boyfriend can install it himself and save the labor charge of having it installed.
I'm having a hard time understanding why it cost so much to diagnose the prob. and why a part was bought and never installed.
What if the guy puts in a new PCM and then says oh thats not the problem?
Shouldn't the IAC be put in first, since we already have a new one?
Shouldn't the Throttle Body Gasket be replaced since tha Throttle Body was taken apart?
Shouldn't that be done before the PCM is replaced?
If the PCM is replaced first won't the new PCM recognize the missing gasket or maybe bad IAC and store the codes?
If anyone knows how to know if a PCM is bad or how to truobleshoot a P0505 trouble code I would really appreciate if that info could be shared.
Any info. is appreciated.
Thank You,
Sherri Belvill