I know about the multiple problems a bad CPS can cause but hadn't heard about the one I experienced last week. My truck unexpectedly failed to shift from 1st to 2nd from a dead stop. The engine would just rev up to 3200 rpms and stay there until I let off the gas, at which point it shifted. At first I thought my tranny was fried. I did some FTE research and most threads indicated a VSS (Variable Speed Sensor) might be bad, but mine was good to go. I spoke with my local tranny guy and he suggested the CPS was bad. I just happened to have my trusty spare CPS with me, changed them out, and the shifting problem stopped. I immediately purchased a replacement CPS and proceeded on my 800 mile trip over mountain passes with my RV, with no shifting problems. $35.00 repair, and a vacation saved! You got to keep that spare CPS in your glove box! It's the 2nd one I've had to replace.

 

Never heard of that one, good to know. I've got 2 spares in my glove box.

 

Way cool! Cheap fix and another piece of good information.

 

X2 what Pete said. I also have a spare CPS.

 

The CPS gives RPM signal. I don't see what that has to do with shift points if the PCM is still making the engine run correctly. Who the heck is your tranny guy? He seems to know more about motors than most Ford diesel techs.

That's the first time I've heard of this (not that it really matters much with my hand shaker). Thanks for the tip machine gunner.

Semper Fi.

 

F350-6: I was surprised as well when he said it may be the CPS. Based on my symptoms, he rattled of three sensors to check. The CPS and the VSS are the first culprits. He stated the tranny is directed to shift based on algorithms from data the VSS and CPS are sending. If either of them are sending bad data to the computer, the computer algorithms get cluster plucked, and send bad shifting data to the tranny. It made sense to me, so I cleaned the VSS with no change. I then changed the CPS, and hot darn the shifting problem corrected itself. Again, the systems were not shifting from 1st to 2nd gear from a dead stop, with either a hot or cold transmission. He listed a third sensor involving the fuel injection system if either the VSS and CPS were OK. I can't remember what that last sensor was called but we didn't get that far. The guys name is Mike and he operates Silverdale Transmissions in Silverdale Washington. I hope it's OK to give this guy a plug. Not only did he fix my problem, but he scanned my truck for codes, drove it around himself, and charged me a big fat zero $ for look see. He saved my families vacation! When my E4OD does finally die, I'm going to him for the rebuild.

Semper Fi and guns up!

 

Glad to hear you got it fixed. And good info.

Semper Fi

 

Ya just might contact him and see if he's interested in joining FTE
Rog