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MindPhish55 04 Apr 2009 12:18 pm

Hi. Great forum, I'm a lurker and have had a few problems with my PT I've always found a solution on this site, thanks. :1st:

I've tried to find some information on this error code (P1685) but really can't find all that much, or maybe I didn't look hard enough. I do know it's an invalid key entry but can't really find how to remedy the problem. I have a 2001 PT and have been getting the code the last few days now, little ding about a mile or so into my trip. Car is running great otherwise...

Thank you in advance and if more info is needed please ask. :D

CREWZIN 04 Apr 2009 03:35 pm

Re: P1685
Welcome to the forum. From PT

P1685 Skim Invalid Key - The engine controller has received an invalid key from the SKIM.

I would not mess with the SKIM. The issue with the SKIM may be tied to the faulty TCM. The TCM is integrated into one module, called the PCM.

SKIM Operation

When the ignition switch is moved to the RUN position, the SKIM transmits an RF signal to the transponder in the ignition key. The SKIM then waits for a response RF signal from the transponder in the key. If the response received identifies the key as valid, the SKIM sends a “valid key” message to the PCM over the PCI bus. If the response received identifies the key as invalid or no response is received from the transponder in the ignition key, the SKIM sends an “invalid key” message to the PCM. The PCM will enable or disable engine operation based upon the status of the SKIM messages. It is important to note that the default condition in the PCM is “invalid key.” Therefore, if no response is received by the PCM, the engine will be immobilized after two (2) seconds of running.

I do not think it's the transponder key. When the faulty TCM/PCM is replaced it may very well resolve the issue with the SKIM. If the issue still exists after the installation the dealer will troubleshoot it with a DRB III scan tool.

MindPhish55 05 Apr 2009 11:39 am

Re: P1685
Thank you. So the problem is most likely the PCM? I have another question.....I've had an error code (P0551 - Power Steering Switch Failure) for about two weeks and still operating the car. (haven't had a chance to take it in) Could this have anything to do with the P1685 code?

I hope I didn't further my problem by not taking care of the first error code.

CREWZIN 05 Apr 2009 12:02 pm

Re: P1685
There is a Power Steering Fluid Pressure switch and they do go bad so that's probably your P0551 code but check or have checked your power steering fluid reservoir to make sure it's topped up.

No, I don't think that has anything to do with the PCM BUT I'm far from an expert so you might want to double check with an experienced mechanic.

MindPhish55 05 Apr 2009 02:00 pm

Re: P1685
Thanks Crewzin for the help. :)

01ltdcruiser 03 Apr 2012 10:28 pm

Re: P1685
Hi Crewzin, I think the SKIM issue is what has happened to my 01 Cruiser as well. My car has been running great and I havent had any problems until today. I left my keys at work and went to leave and used a spare key I haven't tried. It started 3 times but died immediatly (2 seconds) If I come back to it tomorrow with the right key will it start?

CREWZIN 04 Apr 2012 06:50 am

Re: P1685
If it dies within 3 seconds, that's a sign that the security system didn't recognize the right code from the key. Your original key should be OK.

01ltdcruiser 04 Apr 2012 06:55 pm

Re: P1685
Thank you thank you thank you:)!!! My car started with the factory key! Your forum is a lifesaver as a mechanic bill would have finished me at the moment! I really appreciate all the info available here and apologize for the double post!:o


jonwicksy 29 Jul 2014 11:13 am

Re: P1685
Bumping this thread because I am having the same problem. ('02 PT) About a year ago I had to change the ignition cylinder out. I did it myself and now I use a different key. Most of the time when I go to start my car it turns on and the engine hits 1100RPM and then dies... Could this be the same issue and if so how do I fix it?

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