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PLarkinJr
Dodge Dakota
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5/04/2004
21:50:49
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 Subject: Help - P1899 Park/Neutral Switch
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OK, I tried the DIY overdrive inverter at
http://dodgeram.org/tech/mods/transmission/OD_inverter.html
and it works... however, after a while I get Check Engine light, and my OBD scanner shows its throwing a P1899 which Haynes says is "Incorrect input state detected for the Park/Neutral switch". Where'd I go wrong you think?
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PLarkinJr
Dodge Dakota
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5/06/2004
09:33:54
|  RE: Help - P1899 Park/Neutral Switch
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Nothing? Ok, here's more info and what I've pondered: The inverter is a relay with the coil side wired from the starter-relay wire (DB/YL) in the steering column to ground so that the relay is energized when you start the engine. The switch side of the relay is wired from the O/D-Off request switch to ground. The net effect is that when you start the engine, it momentarily "pushes the O/D-Off button for you".
Now, looking at the schematics for the OEM starter circuit, the ignition switch START position send current thru the DB/YL wire thru the coil-side of the starter relay. On the other side of the starter relay is the Park/Neutral switch which grounds ONLY if in Park or Neutral, thus preventing the starter relay from energizing if you are in gear.
So, if I'm understanding this right, my inverter relay gives the DB/YL an alternate path to ground just like the Park/Neutral switch. Could that be causing the ECU to get confused about the P/N-switch? Or might it simply be that my ground on the inverter relay is not good enough (I tapped one of the black ground wires going to the frame-ground bolt under the dash on the left side of the cab)?
P.S. after I clear the P1899 code, it returns after I put the truck in gear the third time I drive it.
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ticats
Dodge Dakota
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5/06/2004
10:04:13
|  RE: Help - P1899 Park/Neutral Switch
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Any transmission related driveability issues or is it just a MIL set/code stored type of thing?
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PLarkinJr
Dodge Dakota
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5/06/2004
10:10:08
| RE: Help - P1899 Park/Neutral Switch
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Drives just fine, and the OD Inverter works as advertised, makes it go "O/D OFF" every time I start it up... and it'll go into OD if I press the button thereafter. Its just that the Check Engine lite comes on, and my code reader says P1899, which Haynes and AllData.com says is the P/N-Switch.
Thanks!
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ticats
Dodge Dakota
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5/06/2004
23:27:51
| RE: Help - P1899 Park/Neutral Switch
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PLarkinJr...from my limited knowledge in this area, I would say that the Park/Neutral circuit has been closed by this inverter mod regardless of the gear selection. This surprises me as I have not come across anything indicating that this would happen. It appears that PCM cavity A6 (Park/Neutral Switch sense) is staying in one state, even when the gear is put in R or 1/2/D it doesn't change, then stores the code and triggers the MIL. Makes you wonder if it will start if gear is in DRIVE.
I was planning on doing this mod myself as I drag race on a regular basis and use O/D OFF frequently in city driving. I'll have my son look at the mod and the wiring diagrams (he has just earned a certificate in this area) but don't know how long before he can get to it. I'll post once he comes up with something. Let me know if you come with anything else as well.
ticats, ontario, canada
97 Dak CC Sport, 5.2L, 44RE,4.56SG, race weight 4,120 lb, 13.98 @ 99.85
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PLarkinJr
Dodge Dakota
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5/07/2004
09:25:45
| RE: Help - P1899 Park/Neutral Switch
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That would be great if your son could come up with something. I've experimented a bit... it wont start if its in drive. I've cleared the code and unplugged the relay wire going to the OD request and the code will return which wasnt a surprise. I replaced the relay and it returned (rules out bad relay). Next I'm going to try it with the only the relay wire going to ignition start unplugged... I'm guessing it wont trigger the code.
I'm wondering if the relay draws too much current on the start circuit, meaning a smaller relay might be better? Or perhaps it creates a short-to-ground so maybe a diode somewhere would fix that? I'm no electrical guru.
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ticats
Dodge Dakota
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5/07/2004
09:57:30
| RE: Help - P1899 Park/Neutral Switch
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Message:
I've been getting a better handle on how relays work and have been looking at the wiring diagram for the Starter System (auto.) in my FSM.
I've been rereading where you hooked up the ground wire to terminal 86 of your relay. It seems to me that you need to tap into the wire running from terminal 85 of the Engine Starter Motor Relay (T41 18 BK/WT in my FSM). This way, the ground from terminal 86 of your relay follows exactly the ground in FSM wiring diagram for the P/N Position switch ... i.e. grounded when gear selection is in Park or Neutral and open when the other gears are selected. I think that you were initially correct when you suspected that your hookup provided a permanent ground for the P/N Position switch no matter what gear was being selected and thus triggering a code and MIL.
Does this make sense to you? If you try rewiring the wire at terminal 86 of your relay as described above and it works, would you let me know :-)
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PLarkinJr
Dodge Dakota
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5/08/2004
10:33:08
| RE: Help - P1899 Park/Neutral Switch
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Well, I understand what you are suggesting: that my relay basically be parallel to the starter relay. I tried it and the relay will not trigger at all, OD still on at start up... I guess path of least resistence is thru the starter relay and/or there's not enuff combined juice on the DB/YL wire to trigger both... So I did a bit more experimentation, and its looking better. Essentially, I ran a wire from the downstream output of the starter relay back to the trigger side of my relay, so when the starter relay triggers, it in turn triggers mine. I'll leave it like that for a few more drive cycles (but I've got over 3 now w/o the MIL code and with OD switching OFF at start). After I feel good about it, I'll post detailed wiring information.
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ticats
Dodge Dakota
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5/08/2004
10:56:19
| RE: Help - P1899 Park/Neutral Switch
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Got my fingers crossed! I'll still get my son to look at it but right now he's going through 5 years of tax filings :-(
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PLarkinJr
Dodge Dakota
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5/09/2004
11:30:08
|  RE: Help - P1899 Park/Neutral Switch
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OK, thanks for all the help here. Details on what I did for the OD Inverter to not throw MIL P1899 are in my post this date on the original thread where the relay suggestion was posted:
http://www.dodgedakota.net/boards/gen/17332.html
Felt it more appropriate to correct the problem info in that thread.
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