Hello there,

I took my 4r100 trans from our 2000 f250 Super duty in to get rebuilt. I just talked to the mechanic, and he has run into a problem that has him stumped. So, the trans is rebuilt and works. It shifts into reverse and can manually shift through all the gears. The problem is when the mechanic puts it in overdrive the input sensor is not reading anything and it wont go into first and is reading a zero. When he manually puts it in first it runs. It is not throwing any error codes and it has him completely stumped. He has never seen this before. So i was wondering if anybody on here had a possible reason for this.

Thanks.

 

Only a guess but was the range sensor calibrated when it was installed?

 

What is an input sensor?

 

Be nice.

You know that he probably means Turbine Shaft Speed sensor, which in many OBDII generic scan tool descriptions for powertrain DTCs in the lower 700 range (P0715, P0717) is commonly and synonymously described as the "Input/Turbine Speed Sensor."

 

I was assuming the same myself. I will use both terms, Input or Turbine speed, since they are the same in regards to the transmission.

The original post is a bit unclear. The turbine or input speed should go to zero if in drive (any gear) and not moving. But he also said it didn’t engage so I’m confused. If it didn’t engage then the turbine wouldn’t stop.

My first thought was incorrect cable adjustment or jacked up plastic clip on the trans lever. But not enough info to make an educated guess in my opinion.

 

I though he meant the TRS. That's why I asked.

 

Sorry for the original post being unclear,

I had my 4r100 rebuilt just last week and my transmission guy called me with a problem that he had never seen before. After he reinstalled the transmission and went to test drive it, he put it in drive and the trans would only start into 3rd gear and not 1st. He was not getting any codes, and he replaced the input sensor, tranny selidiod, neutral safety switch and doubled check the wiring. The tranny will shift into first, but you have to do it manually, and it will drive but you have to shift it manually. The input sensor reads zero when it is park and nuetral, but when put into drive it won't give an input reading until it is revved high enough to start in 3rd. The Input sensor reads normally though when it is put into 1st manually.

This had him stumped and now we are at the point where we think it is the PCM that is going bad. We came to this conclusion because 2 weeks before we had the tranny rebuilt, I had re done the entire front end of the truck and I replaced the old hubs with new ones. The new hubs came with abs lines; however, the old hubs did not have abs hook up on them even though the truck has abs plugs. Not really thinking anything about it, I plug the abs lines into the plug ins on the front driver and passenger sides and about 2 weeks later is when the trans went out.
I am now at the conclusion that when the abs lines got plugged in, it fried the PCM or it was already not good due to the old hubs not having abs lines on them. I am the second owner of this truck and was thinking that the reason the old hubs didn't have the abs lines coming off them was to bypass the PCM.

Sorry for the confusion and thank you for the advice.

 

What exactly are you calling the “Input Sensor”? The sensor I’m thinking of should read zero when in drive and sitting still.

 

The Input speed sensor on the trans.

 

Does he know it is in third gear, or does it just feel like it? I can't see a way for the trans to start in third gear, but I know how it would start in fourth gear.

What you are describing sounds like the solenoid body isn't getting power. There are a couple wires on the transmission connector that supply power. I don't have a diagram to tell you the pin numbers, but they are the red wires. They should have +12 volts any time the key is on.

 

Not all models of these trucks came with front ABS, but the wiring for them is there. That wiring should lead to the ABS module not the PCM so I wouldn't think that the PCM could be effected in any way by connecting the harness to the hall effect sensor in the hub. Of course I could be wrong but I would dig a little deeper before dropping the money on a PCM replacement.

 

I just purchased an OBDlinkex and bought the forscan software to actually see what was going on. This is my first time using this software and I followed the instructions provide in FTE sticky notes, so this is very new to me. I am throwing the PCM code PO741 and while the truck is on and in park the TC_SlipAct, 1/n PID is reading around 466- 500. When I put the truck in drive, it jumps between 736 to 750. While driving the trans starts in gear command one and shifts normally. I watched this on the Gear commanded PID. My trans mechanic was stumped with the numbers on the TC_Slip Act PID, and I think that's what he meant by the trans is starting in 3rd when put in drive. Also, the TCC % PID was reading zero the whole time. I will double check with my mechanic to get a definite answer on what was stumping him now that I have the Forscan software. If there is anything else i should be checking please let me know and I will post the findings.

 

Everything you listed here shows things are working as designed.

 

Does the truck drive and shift ok?

A little explanation about the numbers you are seeing.
TC Slip is going to be the difference between Engine speed and Input Shaft (and Turbine) speed.
—When in Park/Neutral the turbine is free to do whatever it wants so it will spins at a little less than engine speed.
—When you place in Drive the clutches engage and cause the Input Shaft (and Turbine) to stop moving. It is now connected to the output side which isn’t turning so it has to stop. That’s the purpose of the TC, to allow a fluid coupling.
—therefore the TC slip will show the same as Engine speed since Engine - Turbine = TC Slip
— 750 - 0 = 750
–I believe the TCC % PID is showing the lockup command value. Since you aren’t moving it’s not commanding lockup to occur which is why it will show as zero. Get into 3rd/4th gear and you should see it start commanding lockup.

Mark, what’s your thoughts on the P0741 code? That’s TC LU issue correct? Lock up not occurring?

 

All of that is correct.

Correct. When the PCM commands lockup and it doesn't happen, this code will be set. Until the code is cleared the PCM won't attempt to lock the converter again.
If the problem is the torque converter clutch solenoid you'll see a code for a solenoid problem. If the problem is a wiring issue you'll see a code for an electrical circuit fault. Since you didn't mention any of those codes, just the P0741, the problem is either a bad converter, a damaged. or missing seal on the input shaft, or a stuck torque converter clutch control valve. This valve is located in the pump body, so to check all three of these faults the transmission needs to come out of the truck.