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code p1689, no vp needed


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  Hot summer day and the wife take the truck to the store, Her car was in my shop getting a hvac fan motor. She calls me up an hour later, "the truck wouldn't start". I drive over with the shops work van and put the scan tool on. Code p0230 transfer pump circuit out of range, running a Fuel Boss pump with back up electric pump so no big deal.  I clear the code and try to start. The engine turns over not real fast and no start. O'k wife is hot could care less about doing diagnostics and wants to go home. I have it towed to the shop and put the wife back in her Volvo.

   An hour later I turn the key and it starts up with the check engine light on. It's the dreaded p1689 NO COMMUNICATION BETWEEN ECM AND PM.

Take the truck out for a 30mile drive, park it for 30 min. and no start. The engine turns over slowly and then not at all. Batteries are 2 mo. old and voltage is 12.7. Voltage when cranking 10.5-11 then drops to 9. so it's a bad starter motor. The starter motor was replaced 8/21/08 with a lifetime warranty part from NAPPA . I retested with the new starter and no more no more hard /no start hot or code p1689.

  So in conclusion I think a bad starter motor drawing the voltage below operating parameters caused the ECM not to "see" the VP and therefor set code p1689.     What do you think?

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Sounds possible to me.

I worked on a DT444 (7.3 powerstroke basically) and according to diagnostics it was pointing to a bad IDM (Injector Driver Module), but we knew once you got the thing to start everything worked fine so the IDM had to be fine. After doing some research I found that for the IDM to fire the injectors it requires a minimum of 10.5V and when the starter would crank it drew it down below 9V, Replaced the starter and all has been fine since.

Edited by bjytech
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You guys make me like my P-7100 more and more.......

I didn't know they made P-7100 Starter Motors. He he

Sorry MnTom just couldn't resist

Edited by JAG1
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