Hey all, trying to resolve an issue with my franken-truck. For context: its originally a 1993 F-250 5.8L, but I converted the drive train to a 1997 7.3L PSD/E4OD combo. I only got the engine/trans and engine wiring, and had to piece the rest of it together from other trucks, so the PCM I ended up with is a TEE5 from a 1995 truck. The issue I am having is that the computer is never engaging the torque converter clutch solenoid. I have forescan on my phone, so I am able to see live data for the truck. After taking it for a long drive, I verified that all other transmission solenoids are being commanded to operate normally, and the truck shifts fine. However, even when fluid reaches operating temperature, the TCC is still never commanded to operate by the computer. I dont have any check engine lights or stored codes, and the VSS operates just fine. Apparently the function of the brake lights can effect the function of the TCC, so I'm thinking maybe the fact that my truck is a 1993 (Canadian truck is it makes a difference) and docent have a 3rd brake light may be the culprit? Its been like this ever since I did the swap, I've just not started digging into it. Anyone have any clue what could be the cause of my issue? Thanks.

 

Monitor BOO with Forscan. That's Brake On/Off. If it is always 1 the converter isn't going to lock. It should be 0 when the brakes are off and 1 when the brakes are on.

 

Just did another test drive will checking BOO like you said, I also checked the brake pressure switch input for the cruise control while I was in there. Both read as they are supposed to, off (or 0, mine it set to say on/off) unless I actually push the brakes, no sticking or delay in turning off. Earlier I found this TSB that states when the PCM detects a fault in the brake lamp circuit it will output 5-8v on the green brake signal wire. I checked and I don't have 5-8, but i do have 0.08v, so not sure if that actually indicates anything or not. Would love more advice, thanks.

 

Is transmission fluid temperature (TFT) working? If the PCM thinks the trans is cold it will never command lockup.

 

Yeah, TFT is working but only gives me the reading in volts. It does take quite a while for the fluid to warm up, I have a 6.0 trans cooler with a derale thermostat in line, but still takes quite a while to get to ~0.90v, which is where it seems to settle at. Took the truck to work today and still the same issue, even after it warmed up. I haven't yet verified continuity of the wire for the TCC, if there's an issue there would it never turn the TCC on but also not throw a code? It's the lack of any codes that is really throwing me for a loop.

 

If it were an electrical problem it would set a code. The electrical tests are the most robust tests that the PCM runs.

I think Forscan will read trans temp in degrees. Try TOT (transmission oil temperature) which is what the software calls it. I can't translate the voltage to degrees. I remember seeing the transfer function, but that was almost 40 years ago. My memory certainly isn't that good.

 

Thanks, Ill give that a try later. I have been using the chart from this post that indicates that once warmed up my fluid temp is hovering around 200-210, so plenty warm enough. Since I got home ive been poking around in the wiring harness and confirmed that, physically, the TCC solenoid is working. I depinned the wire from the PCM connector and had a helper manually ground it while the truck was in drive and I held the brake. Truck began to die so that confirms the TCC is working, plus I have hear the solenoid clicking in KOEO.

At this point ive ruled out everything else, so I'm thinking its bad programming on the PCM? It was a reman from rockauto so no idea what the programming they put on it actually is, all I know is that it was originally a TEE5. Ill give my local dealership a call tomorrow, hopefully they can reflash the pcm for me.

 

Hope you dont mind me bugging you again, still havent figured out the issues but I did get some new data that may point to a solution.

I realized that I hadn't been looking at the EPC data while I was gathering data the last time, so I took the truck to work today and set up forescan to monitor that as well. Now, its my understanding that the PCM doesn't actually see the line pressure in the transmission as an input, so what forescan displays as the EPC PSI is actually just what the PCM is wanting the line pressure to be based on inputs right?

If so, than it looks normal to me. 5 PSI idle, jumps to 10-20 depending on throttle and gear. I was stuck in traffic mostly so I couldn't give it full beans to see how high it got. What was interesting to me was the EPC voltage reading. I understand from a post you made over on the powerstroke forum back in 2022 that the PCM controls the EPC solenoid by varrying the current. IE, it varies the resistance to ground to control the actuation of the EPC solenoid. So high resistance = low voltage reading on forescan = low EPC PSI right?

Well, I couldn't find anything online that gave me concrete info on what the voltage reading should be, but tagental info found through google implies it should be between 0.5v and 1.5v at idle assuming my previous assumption is correct right? Well, at idle is reads around 9v, and increases with throttle, gear, etc. If these readings are incorrect, could it be pointing to a faulty PCM or EPC solenoid, thus causing the PCM to never activate the TCC? Excessive resistance in the solenoid would lead to a lower than expected voltage reading I would think, so I don't think the issue is the solenoid? What I built the truck im sure I ohm tested all the solenoids in the pack and they tested good, but who knows if they got messed up between now and than to I will definitly check when I get home later.

 

Could it be that the 1997 has PWM controlled solenoid and the TEE5 is on/off?

 

I was sure I checked for that when I originally Ohm tested the solenoid, the PWM TCC solenoid has a different set of values to the non pwm, but it is definitly worth a check again.

 

Correct. The PCM has no idea what the actual pressure is, all you can read is what the PCM wants the pressure to be.

Right.

I don't think so.

1997 was on/off. If it were a PWM TCC solenoid it would still work.
It isn't hard to determine which TCC solenoid is there. The PWM solenoid has about 1-2 ohms resistance, the on/off is around 20 ohms.

 

Just did some reading about the TEE5, seems that you are not the only one with TC lockup issues.
My guess is that the TEE5 TC lockup code just simply sucks.

Others have chipped or reflashed the TEE5 to correct the issues.

I bet if you try a different calibrated DPC-202 hardware like TDE1, you'll find that the trans works better, but engine may not.