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Discussion Starter #1
My 97 died while backing out of the garage and will not restart. Although the tach works while the engine is cranking, I replaced the CPS with a spare I carry in the truck to eliminate anything weird. The CPU had P1670 and a P0603 codes. I have not had time to look into these with any depth yet but I do know the first is a communication problem between the CPU and the IDM. The weird thing is the ICP pressure is over 3200 psi while cranking. If I remember correctly ICP pressure while cranking should be 400-500. Any help would be appreciated
 

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3200 reading makes me suspicious the ICP is defective.

Check the oil level on the HPOP reservoir - get it within 3/4" of the top, then unplug the ICP and try to start it.

Unplugging the ICP will default the pressure to 750 or so psi.

If the HPOP reservoir was completely dry, you may need to purge the high pressure oil system.
 

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Thanks Kimber, I will try those suggestions this weekend. I forgot to mention the "WAIT TO START" light does not come on. I have not had time to research that yet, hopefully this week.
 

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If you have a tuning chip, remove it. We should've done that first thing :)

Check fuse 22 under the hood. Make sure your batteries are fully charged.

Maybe bugman will join in - he knows more about the WTS circuit than I.
 

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Since you are getting a reading on the tach you may have one of those odd ball problems.

Fuse #22 under the hood controls the fuel heater which will short out and blow it. It also supplies power to the PCM relay. So no fuse #22 no PCM functions. That is the strange thing where you say that you don't have a WTS light but the tach registers when turning the engine over since the PCM controls both circuits.

I would check it anyway and if you haven't yet I would unplug the fuel bowl heater to eliminate any problems with that in the future. Also if the #22 fuse is blown unplug the heater before replacing it.
 

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Discussion Starter #6
Thanks for all the suggestions. I tried removing the chip, unplugging the ICP, rechecking the fuses(visually and with a meter) and all where good, switching the PCM and IDM relays with known good ones, and nothing changed. I replaced the batteries a few months ago, they are in good shape and charged. The tach reads about 200 rpm or a little less when cranking the engine, is this correct or should it be higher? If the IPR was not receiving a signal from the PCM, would it default to a higher pressure or a lower pressure?
 

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Did you have oil in hpop reservoir?

I'm not aware of any default pressure built into the IPR.

Make sure you have at least half a tank of fuel in each tank, and switch tanks.

Check your fuel pressure with a pressure gauge at the fuel pressure regulator - look for the schrader valve - should be 50 or so at crank.

If all that checked out, and if it were my truck, I'd give it a quarter-second shot of ether. Many find that advise revolting, but I've been doing it to my `95 for 20 years in cold weather.
 

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I have not had very much time to work on the truck. I was able to use a real scanner and found it will not do a "Buzz Test" or a "KOEO" test, states that there is a communication problem between the PCM and IDM. I was also able to pull additional codes with the better scanner however.

P1663 - FDCS CIRCUIT FAILURE - Indicates that the PCM has detected a failure on the FDCS line
P1667 - IDM Circuit Malfunction
P1668 - PCM/IDM Communications Error

Although I am suspecting an IDM failure, I hope to borrow a break-out box this weekend and check the wiring between the PCM and IDM as well as the injector circuits for problems. Thanks for your help and any advice or information is welcome.

Kimber: Yes, the reservoir has oil, about =1/2" to 3/4" below full. I know it has some fuel pressure because it squirts out of the schrader valve but I do not have a fuel gauge. I hope to have a fuel gauge by next weekend. The fuel tanks are full and 3/4 and switching tanks does not change anything.

Leafit: What do you mean by single click? When the ignition is first turned on or while trying to start it?
 
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