Is the TCC voltage supposed to change when you press the accelerator?

[mcfixstuff]

I have been having issues with my TCC locking up WAY too soon while driving. I hooked a multimeter onto the wire for the TCC on the PCM, and when I'm at idle, it stays at 14.04 volts. When I accelerate the voltage starts to drop, once I am over 20mph, it reads around 2-3 volts, and the TCC engages as soon as it gets over 32mph. Once I am at freeway speed and cruising, the voltage drops and stays steady at 0.22v.

Is this a ECC-IV issue? I can get the voltage to drop by just applying the accelerator pedal in park. The TCC is doing exactly as it's told. The drop in voltage is directly related to the accelerator being pressed, which makes me thing it's not a wiring issue, also considering I did a resistance test on the wire, and it didn't change as I pressed the accelerator pedal.

I have never seen anyone else with this issue. I really don't wanna take it to the dealer and pay the diag fee when it's something I can just fix.

Anyone have any ideas at all?

 

[imp]

I have been having issues with my TCC locking up WAY too soon while driving. I hooked a multimeter onto the wire for the TCC on the PCM, and when I'm at idle, it stays at 14.04 volts. When I accelerate the voltage starts to drop, once I am over 20mph, it reads around 2-3 volts, and the TCC engages as soon as it gets over 32mph. Once I am at freeway speed and cruising, the voltage drops and stays steady at 0.22v.

Is this a ECC-IV issue? I can get the voltage to drop by just applying the accelerator pedal in park. The TCC is doing exactly as it's told. The drop in voltage is directly related to the accelerator being pressed, which makes me thing it's not a wiring issue, also considering I did a resistance test on the wire, and it didn't change as I pressed the accelerator pedal.

I have never seen anyone else with this issue. I really don't wanna take it to the dealer and pay the diag fee when it's something I can just fix.

Anyone have any ideas at all?

You probably have a 4-speed with Overdrive, type A4LD transmission. If the software back then operated similarly to the succeeded transmissions, 4R44E, 4R55E, the TCC should NOT engage until the transmission has engaged 4th. gear, O/D gear, the TCC locking in last, usually around 50 mph. Releasing the throttle (gas pedal) immediately unlocks the TCC, which will re-engage upon giving throttle again, so long as vehicle speed is still maintained. Something is haywire in your trans.

 

[ChildIdenticant]

Have you tried disconnecting the tcc wire altoghether, to analyze behavior during drive?

 

[mcfixstuff]

Ran some more tests this morning. Disconnected the TPS sensor and went for a drive with the CEL light on. Same issues of TCC engaging too soon. Voltage still dipping.
Plugged that back in and unplugged the VSS, voltage kept dipping, but no TCC lock up. Shifted like a dream into 1,2,3, and 4. No TCC, so I was getting higher RPM's on the freeway, but no bucking or lockup at lower speeds. No CEL either. Voltage was still dipping though, which leads me to believe the pin 53 (PPL/YLW) wire on the ECC is not the TCC signal wire, despite the information I found on the internet.
I will go the obvious route and swap the VSS all together.
Will report back.
Anyone know if its okay to go aftermarket on the VSS or do I need to go Motorcraft?
If that doesn't work, I will swap the ECM, with a reman unit.
I mean what else could it be? Can't be a short if it doesn't lock up when I unplug the VSS.
Either the VSS or the ECM.

 

[mcfixstuff]

NOW WAIT A SECOND. It's not the VSS. It wasn't going into 1,2,3,4. It was going into 1,2,3,3TCCL. Put the meter on the 3/4 solenoid, and the voltage never dipped in "4th". Tried to press the gas hard, and it clunked hard out of 3rd lockup into a lower gear. That wire was the correct wire, and something is telling it to engage when it's not supposed to. The solenoid is doing exactly as it's told. It wont disengage when I press the brake, but it'll disengage when I let off the gas pedal, like it's supposed to.
I just placed an order for another ECC. If that doesn't fix it, imma take the L and have a dealership diagnose the issue.

 

[ChildIdenticant]

53 (PPL/YLW) wire on the ECC is not the TCC

Yes, it is.

That wire was the correct wire

Yes, it was.

I just looked at schematics, there are diodes along the solenoids. If the tcc diode failed or is failing..... I think that could explain your issue.
Anyone else confirm?

 

[mcfixstuff]

Have you tried disconnecting the tcc wire altoghether, to analyze behavior during drive

When I disconnected the transmission pigtail, it would shift 1,2,3 no issue. No lockup. I really don't wanna cut and solder any PCM wires if I don't have to. I might as a last resort.

 

[mcfixstuff]

Yes, it is.

Yes, it was.

I just looked at schematics, there are diodes along the solenoids. If the tcc diode failed or is failing..... I think that could explain your issue.
Anyone else confirm?

I don't think the TCC diode is failing, because when I took the valve body off to replace the solenoid (and I did replace it) both the new and old solenoid bench tested perfectly fine. The issue neither got better or worse after the solenoid change.

 

[mcfixstuff]

Have you tried disconnecting the tcc wire altoghether, to analyze behavior during drive?

You were correct. I said **** it and cut the wire at the PCM side. **** still going into TCC lockup, and the voltage still dipping at the live side of the wire going to the solenoid. Switched the meter to ohms to watch the computer enable the ground switch for the solenoid. Sure enough, the computer is doing every it's supposed to. I'm about to do a resistance of the when wire while it's disconnected from the transmission.
I don't think it's the PCM. I think it's the wire. BUT WHERE?

 

[mcfixstuff]

Cut the wire at the transmission side. 1,2,3,4 no lockup. I think I found a winner. Now where the hell would the wire be grounding it's self? I'm gonna try to run my own wire, temporarily to see how it shifts.

 

[mcfixstuff]

ALMOST SOLVED!

Ran my own wire from the PCM to the TCC wire right next to the pigtail that plugs into the transmission, bypassing the factory wire on the harness. Guess what? Shifts like a ****in dream. No voltage fluctuating, 1,2,3,4, LOCK UP BABBBYYYY! Press the brake? Unlock. All symptoms gone.

Here's my delima, do I spend my time trying to trace down where the wire is broken and fix it, or do I rip up the carpet and seats and run my own wire in an organized way along the factory harness?

Is there a common failure point for that harness? I'll do all the work tomorrow, just wanna know what I'm getting myself into.

 

[ChildIdenticant]

Is there a common failure point for that harness?

I think that one goes from trans to connector near charcoal can with no obvious fritction points, then loops through conduit over against top of firewall eventually back around through the firewall on passenger side. Check the firewall passthrough/bulkhead. where harness bundle ceases to be conduit and just wrapped (description of mine).

Don't know if it is common point, just looks most likely to me.

 

[mcfixstuff]

I think that one goes from trans to connector near charcoal can with no obvious fritction points, then loops through conduit over against top of firewall eventually back around through the firewall on passenger side. Check the firewall passthrough/bulkhead. where harness bundle ceases to be conduit and just wrapped (description of mine).

Uhhhh, yeah.... That explains everything. Big long exposed wire is the purple and yellow TCC wire.
Looks melted, not chewed away. Like chemically melted .

 

[ChildIdenticant]

Uhhhh, yeah.... That explains everything. Big long exposed wire is the purple and yellow TCC wire.
Looks melted, not chewed away. Like chemically melted .

fothermu.... And this really shifted fine before warming up?
I don't think brake fluid is supposed to effect the insulation but long term....maybe. And the master is about right above so unless anyone else has insights... Is it soft and gummy or brittle and hard? Or both?

bravo to thorough troubleshooting

 

[mcfixstuff]

fothermu.... And this really shifted fine before warming up?
I don't think brake fluid is supposed to effect the insulation but long term....maybe. And the master is about right above so unless anyone else has insights... Is it soft and gummy or brittle and hard? Or both?

bravo to thorough troubleshooting

Soft and gummy. I had a power steering leak for a long time that I fixed a few months ago. Never had a brake fluid leak thought. Maybe I did, and just didn't know it. I redid the entire brake system last year. I had so many wires like that. My AC high pressure switch pigtail was like that too. I probably went though about 15 to 20 wires, cutting, adding heat shrink tubing to cover the exposed wire, soldering, then covering with heat shrink. Not a fun repair, but I had all the tools and supplies on hand, so it cost me nothing.
Now I notice a substantial increase in power, I wonder if that was also the cause of my fuel economy problems. I'll get back with everyone. Truck drives like it's brand new now.