P0505 Code

[lanesharon]

I changed my IAC, spark plugs, wires, cap, rotor, pcv, and breather. Still get the infamous 'check engine light' with a P0505 code. If it comes on at startup, it stays on. If it does not come on, it stays off. Last week I went to Sears to have the suspension greased. They took off the idler arm to grease between. Oddly enough, the light stayed off all day, through a number of starting and stoppings. Late that night, I started her up, and it came on again.

If it were a short in the wiring, wouldn't it come on and off, during one driving session? If it were a 'sometimes' malfunctioning part, wouldn't it come on and off, during one driving session? This is driving me bonkers.

A friend of mine, today, told me it could be the fuel injectors. He told me to put some STP fuel injector cleaner in the gas tank.

Can someone give me some advice on this unusual situation?

[Dodgevanman]

What is the P0505 description? What fault does that code represent?

[lanesharon]

Idle Control System Malfunction or Idle Air Control Motor Circuits

I have seen both of them listed in manuals. I changed the idle air control system valve. Then did the complete tuneup. It still came on all the time.

Then I changed the pcv and breather. That is when it started coming on sometimes. And the rest of it I explained in my first post on the topic. It is strange.

[lanesharon]

Today, I went through the van again, looking for any loose fittings, or cracked hoses. Nothing. During that time, I disconnected the battery and let the system reset. This afternoon, I reconnected and started it up about 10 times, no MIL (check engine light). Then I put on some gas and let the engine warm a little, turned it off, back on. Now, I got an MIL.

That means that the check engine light is getting triggered when the PCM is in a closed loop operation. It also means that it is starting to monitor the OS2 sensor input. I am going to disconnect tomorrow for several hours again. Then do the whole process all over again. If the MIL triggers only when the car is warmed up again, then I know I am onto something.

I am going to make a grid and attach it here.

[lanesharon]

I looked through the entire PCM section and realize that the only thing that may be different for me is the oxygen sensors. I am enclosing xls document for PCM open and closed loops (engine cold, engine warm). Although acceleration and deceleration revert to open loop mode and the oxygen sensors are ignored, again. YCHHH. If this proves to be true again tomorrow, it means more money, again.

[Dodgevanman]

I hate the fact that you're having troubles, but I'm glad you are posting some observations on what is going on. Maybe somebody can used this info. down the line.

[lanesharon]

Today, I disconnected the battery. Several hours later, I reconnected. Then I decided not to crank the engine over. Instead, over the course of a few hours, I went into the van and turned the key on, but did not turn it to run. I did this 10 times, during each session. Then waited a half hour or so, and did it again. On the 46th time, the engine light came on! That leaves me totally confused as to what this is.

The only thing that I can see that is triggered at key-on only, that might effect the IAC, is the ECT (engine coolant temperature sensor). The PCM sends a signal out to the ECT. From that point on, the PCM only sends out signals to the other elements (IAC, O2S), based on the data it has received from the ECT.

This just sounds like some type of a short somewhere to me. Bad solder, bad connector, or bad engine module. With so many electronic solenoids, relays, sensors, modules, control units involved in this situation, I am totally lost for where to go next. If I take it into a shop, I doubt if they could tell me much more than I already have discovered.

Any advice would be greatly appreciated.

[van-nut]

Sharon -

I totally agree about the shop helping. Some techs are really sharp, and others not so much. I've seen a couple at the so-called 5 Star dealers who left me less than impressed.

The good news is that the van is drivable, right? And still runs decent? And the problem, while intermittant, at least repeats itself.

I'll help if I can. I like challenging problems, and who knows, maybe next week/month/year my van will have the same problem. :WHT:

First off, I've got a factory manual and a supplementary factory manual called "Powertrain Diagnostic Procedures" for my '98 van. As far as I know, there should not be any major differences from '98 to '00. If you need any schematics or anything else scanned and posted, just ask.

I took a look in both manuals, and the schematics show that all 4 wires from the IAC motor go straight to the PCM - absolutely NOTHING in between - IAC, 4 wires, PCM. That's good news.

Also, the description in the big manual for code #P0505 reads "A shorted or open condition detected in one or more of the idle air control motor circuits"

If it is a bad/flakey contact at the PCM itself, look at the 3 big connectors which plug into the PCM - the middle one is called "C2" and pins #10, 11, 19, and 20 should be the four which go to the IAC. I guess it's safe to unhook the battery and let it sit for a bit and unplug that connector to check it. Don't see why it wouldn't be. Just make sure it sits for a bit after you disconnect the battery. And make sure you don't have any static built up in your body which will spark when you touch the van - ESD. Touch a good ground point before you start, and frequently re-touch it while your working around the PCM. Or better yet use a ground strap if you happen to have one.

Oddly, I didn't see anything in the Powertrain Diagnostic book on troubleshooting this code.

Good Luck and keep us in the loop. :gr_patrio

Pete

[lanesharon]

Pete, I work with computers, so I know the importance of grounding. For safety, should I remove both poles of the battery and cap them? Does the PCM keep residual juice (like a monitor)? I don't want to screw up the PCM (way too much money).

Thanks for your help. I am thinking that I will do as you suggested first. Then if I can't find any problems there, I am wondering if I need to clean the throttle body (although it seems pretty clean to me!).

Thanks for your help.

[lanesharon]

Never mind. I am reading the manual on install and removal of the PCM and it says just to disconnect the negative. Then you can check the connections.

[lanesharon]

I think I got it. Today, I went through everything suggested. I knew I had rechecked the new spark plugs, but I got to thinking today that I had not rechecked the wires. I took one of the old wires off and starting changing out one by one. I had a slight ticking in the engine. When I reached number one cylinder (second to last I checked), I put the wire on and the tick went away. I had a bad wire.

That's two bad parts I got from Autozone recently. One was the rotor, which literally fell apart in pieces. Now the wire. Thanks to everyone for your suggestions.

Now, onto the next job - flushing the radiator.

[lanesharon]

I have to rescind my happy dance. I got in the van tonight and the light came on right away, before I even cranked it over. All day it ran fine, no light, with starting and stopping. Not only did the light come on again, but that strange slight ticking sound came back too.

:banghead:

Can someone tell me if I take it to a Dodge dealership, can they do a complete scan that will give them more info than just the DTC's?

[van-nut]

Probably the dealer can answer that question best. I'm no guru on scanners, but I believe the better ones can display most or all of the sensor voltages in real time, and even log the data for later playback.

I guess it might be worth it to explain the whole situation to the service manager and see what he has to say, and decied at that point.

This ticking noise - it only makes the noise with the engine running? Or before you even crank it? And is it ticking many times, like at the engines RPM, or just one tick? And if you clear the code, the tick stops again?

Pete

[lanesharon]

Tick is either in the engine or the exhaust. It was too dark tonight for me to look under the van and get a good feel for which. Oddly enough, it only happens when the check engine indicator light is on. So, all day today, it ran quiet and smooth (no light). Once the light was set on, the ticking came back and it idles a little rougher.

Even though this van only has 50,000 miles on it, do you believe the throttle body needs a cleaning?

Is there a way to clean the oxygen sensors?

I am going to flush the radiator tomorrow, only because I had planned on doing that anyway. I will call the dealership and find out if they can do a more detailed diagnostic scan, with printout. If not, I will then take it to an exhaust shop and have them check that out. One step at a time.

[stev]

Lanesharon,

There is a TSB out on how to properly route the ignition wires. You may want to follow the directions on this closely.

http://www.dodgeram.info/tsb/1998/18-48-98.htm

This stopped my ticking problem and engine light issue on my 2000 Dodge Ram Van conversion by PrimeTime with the V6 3.9L.

And yes, getting cheap wires doesn't help. A 7.5~8mm set would be ideal. I would not go higher than that since more spark being delivered can shorten the life of a basic ignition coil. Only the performance ignition coils work well with the thicker gages. The most important factor here is the wire shielding. Those ignition wire looms are very important to snap the wires in and hold them for these engines.

Even though this TSB is for 94-99, I've found it helpful for both my 2000 and 2001 Ram Vans.

Peace!

Stev

[lanesharon]

Stev, Thanks, I rerouted the wires exactly the way I took them off. I had owned the vehicle for months before this problem came up. But, I will check the TSB.



It dawned on me this morning that there is one consistent thing to all of this. I disconnect the battery negative until the electronic system resets. Then I drive and drive, no problem. But, when I let the engine totally cool down, I get the light.



I know this to be true, because last Sunday I went to a get-together that lasted about 4 hours. All the way there, while gathering up several friends, I never got the light. But, after the engine cooled (while we were there), the light came on. Same thing yesterday. After I get the radiator flushed today, I will try this out again.

[lanesharon]

Just wanted to add one piece of info. I talked to the Dodge dealership today. They have no way of doing a 'more precise' scan on the van. The service attendant told me that they only see what we can already see through the odometer. He did say that they have 'experience' behind them. Also, he told me that they charge $90 to $180 to take a look at it.