ASD components not working.

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09-04-2012 | 02:22 AM

#16

Lunchbox07

Thread Starter

Newbie

Joined: Aug 2012

Posts: 16

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Do I plug it in at the engine harness where I unplugged the old? Also what happens if the dash still doesn't work after I plug the new one in?

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09-04-2012 | 02:25 AM

#17

Radi

CF Veteran

Joined: Apr 2012

Posts: 5,302

Likes: 21

From: Wisconsin

Model: Cherokee

Quote:

Originally Posted by Lunchbox07

Do I plug it in at the engine harness where I unplugged the old? Also what happens if the dash still doesn't work after I plug the new one in?

Yep, plug it in place of the old one temporarily and see if the gauges still work.
I'm betting they do.

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09-04-2012 | 08:58 AM

#18

CCKen

CF Veteran

Joined: Aug 2010

Posts: 8,357

Likes: 90

From: Canton, MI

Year: 1999

Model: Cherokee

Engine: 4.0

Quote:

Originally Posted by Lunchbox07

The fuel pump worked when I unplugged it and tried it. I found on another forum that said. That the pcm sends power somehwere at first turn of key and it goes thru the cps. It said if the cps does not send a signal back to the pcm within a couple seconds the pcm cuts the ground off to the asd and fuel pump relays. So therefore no power to anything. Hopefully will have fixed tomorrow.

It would have probably worked before unplugging the CPS.

Not really. The fuel pump has its own power circuit and does not go through the CPS or ASD.

When the key is placed in the RUN position or the START position, the fuel pump relay control coil is supplied with battery voltage. As the key passes through the RUN position, or when the key is held at the RUN position, the PCM momentarily provides a ground to the fuel pump control coil which closes the power contacts in the relay, powering the pump for 1 to 2 seconds to prime the fuel rail. At this time, the CPS has nothing to do with the fuel pump.

When the CPS signals the PCM that the engine is turning the PCM will provide a continuous ground to the control coil of the fuel pump relay which closes the relay power contacts, providing power to the fuel pump while the engine is running. If the engine stops turning the CPS will let the PCM know and it will remove the ground from the pump relay control coil.

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