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2004 Freestar no communication

8K views 2 replies 2 participants last post by  CatSkinner 
#1 ·
I swear, I want to burn this thing to the ground. She has a P0453 code. This is high voltage on the signal wire for the fuel tank pressure sensor circuit. I dug into it today and I unplugged the connector to the top of the fuel tank, then I pulled the ground wire off the battery and pulled the connector at the PCM above the right strut tower. I had it off and on a few times and I unhooked the battery each time. I also lifted the Bussed Electrical Center (BEC) and tried to find some wiring while troubleshooting the P0453 code.

Now I can't communicate with my scanner to the PCM, the transmission warning light is flashing and it won't crank.

I have a relay or two clicking under the dash - probably the accessory relays in the Smart Junction Box (SJB). I checked fuse 21 in the SJB and it's good, but the PMC controls the ground for the starter relay and I'm sure that's why it won't start. It looks like I need to check fuse 40, 43 and 49 in the BEC first since they supply power to the PCM. And there is the PCM Power Relay.

About those relays... Some can go in either way, and I'm 99% sure I have them in the right way, but the only way I can tell is by checking for key on power at one of the connectors and putting the pin 30 in that slot.

It's gotta be something simple or expensive. Either a blown fuse or a blown PCM.

Any other suggestions?
 
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#3 ·
Ok, I'm trying to piece this together without a schematic and after reading over both posts, I'm wondering if you're looking at this backwards. The pressure sensor is pretty much a transducer. One wire is always hot, one wire is ground and the third is your varying signal.
If they're calling the wire your on a reference signal, that may be your hot wire. I would verify your tank is really not pressurizing, and that your carbon canister and vent line aren't plugged. If the vent line is clear, pull it from your canister and try running it again and see if the diagnostic clears, then put it back on the canister, if it comes back, you may need a new canister.
 
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