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1500 no signal from pcm to asd

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Old 11-27-2023, 09:18 AM
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Default 1500 no signal from pcm to asd

My 2000 Dodge 1500 quit on me and I have traced it back to the asd relay. I have power to the relay (both unswitched and switched) and if I install a jumper wire in place of the two main terminals the truck runs. What I do not have is the ground signal from the pcm to the control side of the asd relay to activate it. I have checked the wire (blue with yellow trace) from the ipm to the pcm and I do have continuity. Is there more I should test or do I need a pcm? Thanks.
 
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Old 11-27-2023, 02:50 PM
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Does the fuel pump prime when you first turn the key on? PCM will only engage ASD for about 3 seconds at initial key on, and then, only if it sees the engine turning.

Since it will run with the relay jumpered, likely not a sensor problem.
 
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Old 11-27-2023, 03:29 PM
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Put a voltmeter on the wire just before the PCM. It should read 12V before cranking and go to 0V during cranking when the PCM is supposed to ground the relay circuit. If it doesn't then it's the PCM.
 
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Old 11-27-2023, 04:51 PM
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Honestly, I’m not sure about the fuel pump. I will check again at initial key on.
Originally Posted by HeyYou
Does the fuel pump prime when you first turn the key on? PCM will only engage ASD for about 3 seconds at initial key on, and then, only if it sees the engine turning.

Since it will run with the relay jumpered, likely not a sensor problem.
 
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Old 11-27-2023, 04:53 PM
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Excellent, thank you. If it doesn’t ground the wire during cranking I will order a pcm.
 
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Old 11-28-2023, 02:03 AM
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Originally Posted by tractorsam
Honestly, I’m not sure about the fuel pump. I will check again at initial key on.
The fuel pump relay and the ASD relay are on separate control pins at the PCM so the pump running is inconclusive. If the PCM turns out to be the problem you could add a relay that is controlled by the fuel pump relay load side and use it to ground the ASD relay control.
 
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Old 11-28-2023, 04:43 AM
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Ok, thank you. I used a jumper wire in place of the asd and drove the truck yesterday, seemed to work fine.
 



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