Transmission Open and Closed Loop Cycle?

[Fordzilla80]

Hey guys, quick question. When the PCM is in open loop, does it also ignore the transmission sensors, such as the solenoids?

My problem is the wonderful, awesome P0741 TCC Clutch Stuck Off code. I have a problem with the idle getting really jumpy at stops and sometimes the truck will just die. It seems I have intermittent lockup, as sometimes I can see the RPMS jump up and down, but other times I see nothing. The catch is, the truck runs absolutely great when it's cold, but as it warms up, it gets worse until the point where the idle is so jumpy the truck is barely driveable due to the risk of it dying. What I'm wondering is if my TCC solenoid has an issue, is the truck running fine when it's cold because the PCM is ignoring input from the solenoid, or could it be that one of the valve body gaskets is damaged, closing up when it gets cold, but expanding as it gets hot, just as a vacuum line would?

 

[PopRichie77]

There are many things that can cause a P0741 code, so there is no specific answer. The first thing would be to drop the pan, remove the valve body and replace the gaskets and TCC solenoid, along with a new filter and fluid.
The computer doesn't go into open or closed loop. When cold it doesn't try to lock the TC until a certain temperature. Then after about 3 failed a temps, it goes into ( Failure Mode Management) commonly called Limp Mode and flashes the OD light, it may also reduces engine power to prevent further damage to the trans, it usually doesn't effect idle.
TC could be bad, seals for the TC on the pump could be bad, or too much internal leakage could cause no TC lock up.

 

[Fordzilla80]

Ahh I see. All good things to check. I can see how the computer keeps O/D out until the trans warms up. But the biggest thing that confuses me is that there are absolutely no symptoms when the truck is cold. If I had a bad separator plate gasket or a faulty TC, wouldn't these issues show up when the truck is cold as well?

 

[PopRichie77]

The fluid is thicker when cold, thus not as much leakage, when warm it is much thinner and leaks more.

 

[Fordzilla80]

Ahh that makes sense.

While playing around with it today, I noticed the problem gets better if I shut the A/C off. It only fluctuates a little bit, and doesn't seem to try and die. Another thing, if I put the truck in Neutral at stop lights, the idle goes right back to normal and the truck will idle fine. Then when I put it into drive, introducing the load, it does it's whole routine again. I also paid more attention to the hesitation it has, and it seems like the truck pops into neutral when I accelerate, but then it kicks back into drive. However I don't feel the gear change, it just seems like there's a moment of non-response, as if my throttle position sensor has a dead spot. And the last thing I noticed is that my brake switch is incredibly noisy. Kinda sounds like dry rusty metal is rubbing together. How does the computer know when to unlock the torque converter? On some vehicles I know the brake switch has function over this, But is this how it is on the Rangers? I need to shut that brake switch up, so if it has something to do with the T/C unlock, then lubing it up may be a cheap way to rule out a possible cause.

 

[PopRichie77]

Part of the brake switch is for the TC, it unlocks any time you touch the brake peddle. It also unlocks when you release the gas peddle. Also unlocks based on the trans speed sensor and the MAF sensor.
I don't think your idle problem has anything to do with the trans.

 

[Fordzilla80]

Part of the brake switch is for the TC, it unlocks any time you touch the brake peddle. It also unlocks when you release the gas peddle. Also unlocks based on the trans speed sensor and the MAF sensor.
I don't think your idle problem has anything to do with the trans.

I'm really hoping my idle problem has nothing to do with the transmission.lol. Back when this first started, I pulled all the plugs and inspected them. The plugs had normal wear, with no signs of running rich or lean, however the gap on the plugs ranged from .070 to .080, when they should be between .042 to .046. I re-gapped them for the time being, but ultimately they'll need to be replaced. Both the plugs and plug wires are original, and the truck runs a little rough, and may have a slight miss, but I've never experienced a vehicle with a miss, so I'm not really sure what that feel/sounds like. If I'm lucky, the plugs will take care of it. However I'm still gonna eventually invest in the valve body gaskets, all the updates, TCC and EPC solenoids, and possibly a shift kit. It's just safer security.

I really appreciate the help PopRichie.

 

[cowboykilroy]

Have you cleaned the idle air control valve? I have an 01 ranger edge 4x4 having idle issues and cleaning the IAC fixed it. My wifes car is an 05 escape w/auto and after driving 30+ miles when you come to a stop the t/c would not unlock and it would kill the engine unless you put it in neutral.no codes, no flashing od light. M trans man tried a few things to save me $ a flush and additive,then solenoid pack. went with complete rebuild and new T/C .all is good. good luck

 

[Fordzilla80]

The 5R55E has an internal thermostat that opens the external ATF cooling loop when the torque converter temperature reaches 150 degrees. If the transmission shifts normally when cold but poorly when warm that may be an indication of low line pressure.

Okay, well I ran across that post from another member on here that detailed one of my issues to a tee. Judging by his description of low line pressure causing the transmission to run better when cold, and the symptoms my truck is presenting, I'm pretty sure I'm facing transmission issues. Unfortunately, the only code I get is P0741 for the TCC circuit performance or stuck off, and that only seems to come on when I maintain a steady speed. I do not believe that my T/C is unlocking, as tapping the brake and gas does not provide a change in the rpms. The transmission seems to go into every gear when it should, and it seems to downshift fine, although some of my shifts are occasionally rough when I go wide open throttle.

There are a few things I am thinking at this point.

-T/C Solenoid is faulty, be it the wiring, the solenoid, etc.
-EPC solenoid is faulty, be it the wiring, the solenoid, etc.
-I may have blown the valve body gasket out. Luckily, I replaced the trans filter about 2 months prior to my symptoms, so if I did blow the valve body gasket(s), then I should find remnants in the new filter element.

Gonna do a little research to see if there is a way I can measure line pressure, but ultimately it looks like I will be entertaining the valve body in the near future. My truck hasn't even reached 50,000 miles yet.

 

[PopRichie77]

You need a 300 psi gauge and connect it to the line port, also you can connect to the EPC port and check that. However line and EPC pressure can be in spec and the torque converter still will not lock up, pressure can be lost after these ports so that there is not enough pressure to lock the TC. I know this for a fact cause I had a p0741 code replaced all seals that are specified for the Torque converter also replaced the Valve body with one from Central Valve Bodies, replaced the Torque Converter and still had no lock up. But you should replace the things you indicated above first. Which may solve your problem.

 

[Fordzilla80]

Yep, I'm gonna have to go on quite a shopping spree just to figure this out. It wouldn't piss me off as much if I were richer and had another truck to drive while this one is down. lol.

I've read on a few different articles that unplugging the connector on the trans disables lockup, but I don't see the need to pull all 13 connections. Do you think that I could possibly pull the pin for the TCC solenoid wire and take it out of the connector and then go on a test drive to see if that unlocks the T/C?

Actually, looking at my wiring diagram book, it looks like the EPC solenoid and the Transmission Fluid Temp sensor both have their own separate wires as well. Previously I had to replace the main trans connector since the dealer that pulled the trans to replace the rear main seal before I got the truck broke it in two spots. I'm wondering if maybe some combination of these wires shook themselves loose somehow? I know that when the guy sent me the new connector, some of the locking pins were weak. That may be something I want to check on since all of this did start after I went through a bumpy mud hole. If no input is sent to and from the TFT sensor, then I guess that could cause my good when cold bad when warm issue, and could throw off information to the other parts? Or maybe the other connections being loose are presenting their own problems?

 

[Fordzilla80]

Just as an update, I changed the plugs and wires yesterday, and it seems like the jumpy idle is about 85% reduced. Idle still hunts a little, but it's not a major jump like before. The IAC still seems to function fine, as when I pull the connector the truck idles down to around 400 close to stalling.

I also crawled under the truck to check the main connector for the solenoid wiring, and it seems like everything is in check there. Couldn't find any loose connections anywhere. I did clean the mud off the connector. Not sure what made the jumpy idle lessen up, be it the new plugs and wires, or adjusting the trans connector. Gonna go out this week and remove the TCC wire and see if the truck behaves any better/worse. Still no O/D Off light or Check Engine Light which annoys me quite a bit. There's no point in having OBD II if it can't even recognize a serious problem.

Two things that I have also noted is a distinct clunk coming from either the front u-joint or maybe the slip yoke. I have never greased either in the 7,000 miles I've had the truck, so definitely need to take care of that. Also, the brake pedal switch on the pedal stalk is incredibly noisy, like a rusty e-brake release handle on an older F-series truck. Need to pull it off and see why it has gotten so noisy.

 

[Fordzilla80]

Alright so pulling the TCC wire from the connector threw the O/D Off light as soon as the truck was started, so that means that my O/D Off light still works, and that the computer is trying to respond with the TCC solenoid up to that terminal. I realized the other day that I still have 5 quarts of Mercon V in the shop, so sometime next week or so I will go out and grab a new filter and gasket, and then pull the pan, pull the filter, check all the solenoid connections, ohm out the solenoids, possibly check the EPC and TCC solenoid screens, and then take apart the old filter and inspect the filter element to see if I can find any gasket remnants or other materials. If I do, then I will know where I stand. If not, and everything else checks out, I'll have to move on to line pressure tests.