Join Date: Dec 2008
Location: Tyler, TX
Thanked 407 Times in 347 Posts
The E4OD/4R100 are electronically controlled transmissions. The "PCM" is the computer that controls both engine and transmisson functions, hence the "Powertrain" part of Powertrain Control Module.
When you LIE to the PCM about ICP (forcing the sensor LOW), it compensates by increasing the IPR duty cycle (or Pulse Width) until the ICP voltage is back to where the PCM expects it to be. This causes more fuel to be injected (more pressure + same "On Time" = more fuel) than the PCM believes is being injected.
The PCM works off of "look-up" tables for things like timing, trans line pressure, shift timing, converter lock-up (both pressure and timing). ALL these tables are based on engine LOAD.
Since the PCM thinks LESS fuel is being injected than actually is being injected, it believes also that the LOAD is lower.
Result, late shifts, soft whifts, line pressure lower than SHOULD be there, converter locked/unlocked when it should not be, and slipping. All this leads to trans failures.
Now, there are a handful of people who are "very knowledgeable" on the interactions of the PCM, engine and transmission. Two still work for SCT, the other is off on his own again, and is a former Ford transmission engineer.
NONE would ever suggest a mod such as this, and all can explain in greater detail than I about the reasons why - I have just scratched the surface.
'93 F-250 HD, 7.3L IDI, 5spd - FARM TRUCK
I Support: Trailer brakes an every axle over the towing vehicle's GVW; CDLs for RVers; Safety inspections for ALL vehicles and 6 axle trucks (97K GVW proposal).
Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote - Benjamin Franklin
I vote for LIBERTY!