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Ford F350 Diesel - Forced Idle

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New User

Apr 13, 2010, 1:02 PM

Post #1 of 4 (1979 views)
Ford F350 Diesel - Forced Idle Sign In

F350 SD
6.0 V8 Diesel

Problem: The scanner kicks out DTC for the MAP sensor, MAP/BAPP sensor and the EGR sensor. The likelihood of all 3 sensors being out is extremely slim. The PCM Reference Voltage which is connnected to all 3 sensors intermittently drops from 5 volts to 1 volt or less. This is causing engine to run in a forced idle mode (no rev when gas pedal is depressed) and/or stall out. When 5 volt Reference Voltage is restored all engine lights go out and truck runs normally. We have already replaced the Accelerator Pedal & Sensor. We have swapped the PCM (with a used one) and the FICM (also used) and the problem still exists. Ford has advised that the F Series trucks have known issues with the control modules so we are still suspecting the PCM is a problem. Has anyone else run into this or do you have any suggestions?

Veteran / Moderator

Apr 13, 2010, 6:09 PM

Post #2 of 4 (1968 views)
Re: Ford F350 Diesel - Forced Idle [In reply to] Sign In

you've really done your homework testing this problem out. Thanks for that. I have heard of the 6.0 diesels having defective PCMs and it makes it hard to trust a salvage unit because of that. The PCM is what delivers the 5v reference, and this looks like a cut and dry case of PCM failure. Being that Ford knows their part is defective, its possible you may convince a dealer to replace it as an extended warranty or policy repair. At the very least, the company may give you a break on the price

New User

Apr 13, 2010, 6:17 PM

Post #3 of 4 (1967 views)
Re: Ford F350 Diesel - Forced Idle [In reply to] Sign In

Thank you for the reply Nick, it's nice to hear someone else who knows their stuff is of the same mind. Ford is now taking back the PCM units with a core return which shows to us that they are finally testing the units for possible causes to the problems. They aren't offering much more in the way of a price break and this truck is long off warranty.
We were hoping to see if anyone else had run into this Forced Idle issue before. We are currently awaiting another used PCM unit and if this one fails we will have to break down and go for the new one. Have a great day.


Apr 14, 2010, 9:08 PM

Post #4 of 4 (1957 views)
Re: Ford F350 Diesel - Forced Idle [In reply to] Sign In

have seen problems with the pcm as well.but also double check grourds as well have seen those cause a issue in a few cases as well.

Ford F350 Diesel - Forced Idle

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