1999 Dodge Ram RPM Signal
Printed From: the12volt.com
Forum Name: Vehicle Wiring Information & File Requests
Forum Discription: Request Car Alarm, Car Stereo, Cruise Control, Remote Starter, Navigation, Mobile Video, and Other Vehicle Specific Wiring Info, Manuals, Tech Tips
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=145388
Printed Date: May 02, 2025 at 2:35 PM
Topic: 1999 Dodge Ram RPM Signal
Posted By: thetinman86
Subject: 1999 Dodge Ram RPM Signal
Date Posted: April 27, 2019 at 5:58 PM
Hello all! I’m working on a little project using an arduino to remote start a vehicle and I’m looking for an rpm signal I can work with. I see the what people use for traditional systems is the black / grey wire on the ignition coil. I have no oscillascope to see what the waveform is. Ideally I would like a 5vdc pwm. Any advice would be appreciated. Thanks in advance.
Mike
Replies:
Posted By: i am an idiot
Date Posted: April 30, 2019 at 5:53 AM
Did you try the black/grey wire?
Posted By: Ween
Date Posted: April 30, 2019 at 6:52 PM
https://api.motor.com/v1/Information/Vehicles/Attributes/BaseVehicleID/1902/Content/Documents/Of/WiringDiagrams/7714332?Scheme=Shared&XDate=1556668326&ApiKey=YWWodJ8Irm&Sig=UAVXJqvsf2SDEUKnGfoIzCsNt1fcOHre35PpV6iLbUM%3D
Posted By: thetinman86
Date Posted: May 02, 2019 at 8:27 PM
Yeah I checked that wire. I can’t tell what the signal is but the voltage is too high. I think I’m going to check the crank sensor wire. That wire should go to the PCM module on the passenger side fire wall.
Posted By: thetinman86
Date Posted: May 02, 2019 at 8:29 PM
Sorry ween I can’t open that link for some reason.
Posted By: Ween
Date Posted: May 02, 2019 at 8:35 PM
Oh well....PCM connector C! pin 8 maybe? gray/black ..Crankshaft Position Sensor Signal
Posted By: i am an idiot
Date Posted: May 02, 2019 at 9:30 PM
How much too high is the voltage? A simple 2 resistor voltage divider will work.
https://www.ohmslawcalculator.com/voltage-divider-calculator
Posted By: thetinman86
Date Posted: May 06, 2019 at 6:34 AM
I thought of this as well however I have no idea what the signal is to design this voltage divider. I measure on AC an get +20V when revved and when on DC 4V? Seems weird so I am trying to stay away from this wire. The PWM signal I can get from the crank sensor I think is best. Hopefully I can try this out tomorrow. Next is door locks and starting! Again, thank you both for your input!
Posted By: thetinman86
Date Posted: May 06, 2019 at 9:52 AM
Just out of curiosity is there anything else I could use as a "run" signal that would be better or easier than the crank sensor? I don't really need an exact RPM. Just looking for something to say hey I'm running don't try to start again.
Posted By: thetinman86
Date Posted: May 07, 2019 at 1:26 PM
Another question. Does anyone know the minimum voltage for crank sensors that produce an AC output signal? I know the magnitude will increase with RPM but what is the minimum at idle?
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