Hello,I have a high idle problem on my 99 Durango 5.2litre. It is returning a P0505 error, I have replaced the IAC and the TPS, I have removed and cleaned the throtlle body but the check engine light is still on. It seems to idle fine untill it warms up, then the idle will shoot up to about 2000 RPM. The only part on the throttle body I have not replaced is the MAP sensor, at a $110I would like to know if it would be the next step or if there is anything else I can look at. I would like to add that it does not idle high all of the time, sometimes it runs and idles perfectly, but the check engine light remains on all the time. All and any help is greatly appreciated. Thanks!

I have the same issue on my 99 with the 5.9L engine. I have cleaned the battery terminals, replaced the plugs, wires, vacuum hoses, PCV valve, IAC and TPS. I have also cleaned the throttle body and put on a new throttle body gasket. I also get the P0505 code. I'm not sure what to look at next. It runs at 700-750 RPM when cold and then moves up to 1,000-1,000 RPM as it warms up. Anyone?

505 indicates an IAC driver circuit is shorted to ground or one of the other drivers. This can be a defective IAC (obviously not for either of you), a problem in the wiring harness or at the PCM connector.

Only thing to do now is test circuits and find out which driver is shorted to what. I would carefully inspect the exposed wires and loom to make sure none of them have rubbed through to gound or each other. If you don't find anything (without actually tearing apart the whole loom, provided it appears in good condition), start probing.

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Thank god Ford is still making vehicles, because mechanics still have bills to pay.

Thank you very much for the information. I will check the wiring today and post results. Is it easier to simply replace the harness or is that not an option?

I don't see anything obvious. If I take a voltmeter, do you know what the readings should be for each lead?

I checked all the wiring yesterday and could not seem to find any problems, they all seem in tact and working properly. What is strange is that it runs great with normal idle most of the time and it is only after it warms up that the idle will stay high. Could it be a vacum leak or a oxygen sensor? I was going to replace the PCM, but it seems that it would fail all of the time and not just some of the time. I might take it to our local shop this week as I am out of answers. Thanks for the help and if anyonehas any suggestions they would most certainly be appreciated.

Try replacing the crankshaft speed sensor that can sometimes ground itself...after that its the PCM...Chris

Thanks Chris, I will try that. I am trying to hold out on the PCM, I found one for $250 and almost purchased it, but would like to get the less expensive stuff out of the way first. I'll keep you posted.

I replaced the crankshaft position sensor today and it did not fix the problem....so I guess it's either take it to the shop or replace the PCM which is a real easy job. I'm just not sure if I should spend the $250 for the PCM or try our mechanic. It seems that only when the D warms up it starts to idle very high, somewhere in between 1500 and 2000 r's. Any other suggestions would be appreciated as I have tried all the easy stuff and am now thinking I should maybe leave it to the experts.

Well I took mine in for a diagnostic. It cost me $110. They say it is definitely the PCM.

Any recomendations for aftermarket ones to replace it with?