Ford PWM Idle valve circuit is not working
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Ford PWM Idle valve circuit is not working
I've posted a question on this subject once before and have had no luck getting my fast idle valve to work. I am running a ford 302 with MSII V3 board and 2.891 code version. I've tried every type of setting in both frequency and valve duty cycle table. I know my external wiring is correct because I've jumped the center lead (B) of the transistor TIP120 and the (E) lead which goes to ground and the valve opens. I also checked each lead of the transistor and (B) goes to pin 30 DB37 12V key on and (E) is grounded which leaves (C) which has 0 volts key off and jumps to 4 volts for a second then .3 volts until the engine is started then remains at a constant 5.85 volts. Doing this same test on the simulator and changing the duty cycle numbers I can swap the voltage ranges. I believe the transistor is not damaged from tests with the simulator, but I am not sure. Is there a easy way to test without removing the transistor from the MS? Does anyone know what the signal would look like going to pin (C) from the daughter card? Should it be a constant voltage that decreases as temperature increases? Or since its a Pulse Width does is have a square wave signal where I need a oscilloscope to determine pin (C) is getting the correct signal? The attached image is from the Mega-manual that shows the PWM idle valve transistor modification. Any help that could give me further troubleshooting ideas would greatly be appreciated.
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Matt Cramer
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Re: Ford PWM Idle valve circuit is not working
The signals involved are square wave signals - some multimeters may average them and interpret them as a variable voltage, others may behave a bit differently. If you test it on a Stim, can you change the intensity of the FIDLE LED by turning the CLT trim pot?
Re: Ford PWM Idle valve circuit is not working
I've tried it on the simulator and the led gets bright or dim depending on which way the coolant pot is turned. That's what is so confusing on the sim it seems to be working like it should, but in the vehicle the valve doesn't work unless I bypass the transistor. The only thing I can think of as my next step is to hook up a oscilloscope to see if the incoming signal is correct on pin (C) of the transistor or replace the transistor. So when I get a hold of a oscilloscope the signal I should be getting is a square wave and the frequency should match what is set in Megatune which is 320Hz currently.