code p1668 help - PowerStrokeNation : Ford Powerstroke Diesel Forum
 
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post #1 of 6 (permalink) Old 09-21-2008, 10:03 PM Thread Starter
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code p1668 help

I am working on a 96 that is throwing the p1668 code it says pcm-idm communication. I have tested the pcm and the idm on different trucks and they are fine. What other components can I check?

01 F350 cc dually 6sp conversion
00 F250 2.6 puller
early 99 F350 2wd daily driver
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post #2 of 6 (permalink) Old 09-23-2008, 05:08 PM
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Re: code p1668 help

DTC P1668 and P1670 indicates that a communication error has occurred between the PCM and the IDM.
Possible causes:
Open fuse
IDM relay
Open or shorted IDM enable circuit
Open/short in EF circuit
Open/short in FDCS circuit
IDM powering circuits
PCM
Check for other codes

Rick....

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post #3 of 6 (permalink) Old 09-24-2008, 12:18 AM Thread Starter
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Re: code p1668 help

no other codes. I changed around the relays and the truck srarted, but now it has a short in it. The wait to start light flashes constantly and the lights in the dash flash. It's almost like you are turning the key on and off really fast.

01 F350 cc dually 6sp conversion
00 F250 2.6 puller
early 99 F350 2wd daily driver
smokin dually is offline  
post #4 of 6 (permalink) Old 09-24-2008, 12:43 AM
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Re: code p1668 help

Just for drill disconnect the fuel heater. They like to fail and short on out the PCM circuit but I have not read of anyone having this exact set of problems. I would also be checking out those relays.

Tom

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post #5 of 6 (permalink) Old 09-25-2008, 12:46 AM Thread Starter
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Re: code p1668 help

I will try new relays tomorrow

01 F350 cc dually 6sp conversion
00 F250 2.6 puller
early 99 F350 2wd daily driver
smokin dually is offline  
post #6 of 6 (permalink) Old 09-27-2008, 02:26 AM Thread Starter
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Re: code p1668 help

It was the relay.

01 F350 cc dually 6sp conversion
00 F250 2.6 puller
early 99 F350 2wd daily driver
smokin dually is offline  
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